Helioseismology

Main Colloquium
Prof. Laurent Gizon
CANCELED
Max-Planck-Institut für Sonnensystemforschung, Goettingen

How does the solar dynamo work? In order to address this challenging question, we need to understand all the components of motion that maintain the magnetic field in the solar convection zone, using helioseismology. Solar acoustic oscillations have been observed nearly continuously at high spatial resolution for over 20 years by dedicated observatories from space and the ground. The science of helioseismology consists of interpreting the frequencies, amplitudes and phases of the oscillations seen at the surface to make 2D and 3D images of the flows in the solar interior. Important results include, for example, maps of internal rotation (as a function of radius and latitude) and flow patterns associated with convection and magnetic activity. In this presentation I will especially report about the very recent discovery of a new component of solar dynamics at large spatial scales: global equatorial Rossby waves.

High precision pulsar timing

Promotionskolloquium
Eleni Graikou
ORATED
MPIfR

Pulsars are rapidly rotating, highly magnetised neutron stars, remnants of a supernova explosion. The majority of the science that we can do with pulsars comes from a technique that is called pulsar timing. Millisecond pulsars, which are pulsars with spin periods of only few milliseconds, are ideal objects to apply timing since their rotational stability on long timescales approaches that of atomic clocks. Probably one of the most interesting application of pulsar timing is the detection of gravitational waves (GWs) in the nanoHz regime with pulsar timing arrays (PTAs). The main source of red noise in pulsars that potentially blocks the detection of GWs with PTAs is chromatic variations produced by perturbations in the interstellar medium. In the first part of the talk I will focus on the usage of the Effelsberg and MeerKAT high-frequency receivers on measuring these dispersion measure variations and increasing the sensitivity to GWs. Even though GWs have been directly detected with LIGO, the first observational evidence of their existence came from the study of the first binary neutron star system ever discovered, PSR B1913+16. In the second part of this talk, I will present the effect of the relativistic geodetic precession on the total intensity profile and polarisation properties on this pulsar. As well as our study about the shape of the emission beam. Finally, I will show the timing analysis of a pulsar-white dwarf system, PSR J1933-6211 and present its evolution. [Referees: Prof. Dr. Michael Kramer (Max-Planck-Institut für Radioastronomie), Prof. Dr. Norbert Langer (Argelander-Institut für Astronomie, Universität Bonn), Prof. Dr. Klaus Desch (Physikalisches Institut, Universität Bonn), and Prof. Dr. Barbara Kirchner (Mulliken Center for Theoretical Chemistry, Institut für Physikalische und Theoretische Chemie, Universität Bonn)]

Deep, Large Scale Surveys of Star Forming Regions throughout the Milky Way

Promotionskolloquium
Carsten König
ORATED
Max-Planck-Institut für Radioastronomie

Star formation and the processes involved are not only important to the Milky Way as an astronomical object, but are also crucial to understand our own origin. For instance, only lower-mass stars like our own Sun have supposedly a long enough lifetime to allow for the development of life, whereas high-mass stars are the major source of the heavy elements like iron, that are needed to form life as we know it. Therefore, understanding the influence of the Galactic environment on low- to high-mass star formation is crucial to understand our own place in the Galaxy. In this work we have investigated star formation throughout the Milky Way - from the inner parts to the far outer Galaxy, ranging from a small, well selected sub-sample up to a complete sample of massive star-forming regions. We used several different dust-continuum surveys (ATLASGAL, Hi-GAL, MSX and WISE) to obtain photometric data, and consecutively model the spectral energy distributions of the dense molecular clumps in which stars and star clusters form. From these we derive the physical properties such as dust temperatures, integrated fluxes and H2 column densities. We derive distances from line-of-sight velocities obtained from CO observations for the majority of the sources, allowing us to calculate clump masses and bolometric luminosities and analyze the properties of the sources in the context of their large scale Galactic environment. [Referees: Prof. Dr. Karl M. Menten, Prof. Dr. Pavel Kroupa, Prof. Dr. Klaus Desch, Prof. Dr. Hubert Schorle]

The Breakthrough Listen Initiative: Determining the Prevalence of Technologically-Capable Life

Special Colloquium
Dr. Andrew Siemion
ORATED
Berkeley SETI Research Center

A revolution in our knowledge of the exoplanet population has brought with it the incredible realization that our galaxy is awash in oases for life. Coarsely speaking, it is now clear that all of the necessary precursors and preconditions for life to arise exist in abundance throughout the cosmos. Knowledge of these facts has sharpened our scientific curiosity about whether or not life has indeed arisen elsewhere in the universe, and if so, whether any of that life evolved the same capacity to probe and contemplate the universe as human beings. The search for extraterrestrial intelligence (SETI) seeks to answer this question by conducting searches for direct or indirect effects of extraterrestrial technologies, so-called “technosignatures.” At the forefront of these experiments is the Breakthrough Listen Initiative, a 10-year research program that is conducting the most comprehensive, intensive and sensitive search for extraterrestrial technologies in history. Breakthrough Listen employs radio and optical telescopes around the world and is developing sophisticated algorithms to sift through massive amounts of observational data. Here we will review the current status of the Breakthrough Listen program, including both existing facilities and nascent engagements with new telescopes and datasets just coming online. We will also present some highlights from the ancillary science made possible by Breakthrough Listen instrumentation and analysis methodology, especially in the area of fast radio bursts

Neutrino Emission from Blazars

Special Colloquium
Dr. Markus Boettcher
ORATED
North-West University, Potchefstroom, South Africa

The recent detection of the very-high-energy neutrino IceCube-170922A in spatial coincidence with the BL Lac object TXS 0506+056 around the time of an extended high state of this source, marks the best evidence so far for blazars being a source of astrophysical very-high-energy neutrinos. In addition, an extended neutrino excess (flare) was detected from a position consistent with the position of this blazar in 2014 - 2015, during a time of quiescence in electromagnetic radiation. This association provides evidence for the acceleration of hadrons to ultrarelativistic energies in the jets of active galactic nuclei (AGN). It may support hadronic emission models for blazars and suggest AGN as sources of ultra-high-energy cosmic rays. This talk provides a general overview of hadronic emission models of blazars and their associated neutrino emission predictions. Recently published papers discussing the connection between TXS 0506+056 and IceCube neutrinos will be critically reviewed.

Galactic Gamma-ray Astronomy in the Advent of CTA

Main Colloquium
Prof. Olaf Reimer
ORATED
Institut für Astro- und Teilchenphysik, Leopold-Franzens-Universität Innsbruck, Austria

Progress in observation and theory allows to study Galactic sources of Cosmic Rays in ever increasing numbers, variety and phenomenological complexity. We are presently witnessing complementarity between deep studies of individual sources and population aspects, and Galactic source physics reaching out into the extragalactic domain. Some source classes evade such generalization owing to uniqueness (Galactic Center), challenging complexity among the class constituents (e.g. gamma-ray binaries), or absence of firm identification (e.g. young stellar cluster). I will review properties and phenomenology of Galactic sources in the interplay between observations and concepts of particle acceleration. Scientific problems raised or left unaddressed by current gamma-ray instruments (Fermi-LAT, HESS/MAGIC/VERITAS, HAWC) will be contrasted with the science prospects of the upcoming Cherenkov Telescope Array Observatory.

HL Tau @ low tau: dust properties from multi wavelength ALMA and VLA observations

Informal Colloquium
Dr. Carlos Carrasco Gonzalez
CANCELED
Centro de Radioastronomia y Astrofisica, CRyA-UNAM, Morelia, Mexico

New high quality millimeter observations of protoplanetary disks have radically changed our view of disk evolution and planet formation. Now, we know that most protoplanetary disks present substructures in the dust in the form of high density rings. Understanding how these structures are formed and how they will evolve has become fundamental in order to unveil how planets are formed. A necessary first step is to obtain the properties of dust in the disk. However, even with ALMA, this is still difficult. Most of the dust in protoplanetary disks seems to be located in very dense structures which are optically thick at ALMA wavelengths. Then, obtaining the dust properties requires a complex modeling and a lot of initial assumptions. This could be solved if high quality observations at an optically thin wavelength are added. I will show some preliminary results we obtained in the case of HL Tau. This is not only the disk that changed our vision of the field four years ago, it is also the disk with the most complete set of millimeter observations at high angular resolution. We have analyzed these data to obtain the dust distribution in the disk without any modeling and with a minimal number of initial assumptions. I will discuss them in the context of planet formation.

AGN torus detectability at sub-millimeter wavelengths: what to expect from ALMA continuum data

Special Colloquium
Dr. Alice Pasetto
ORATED
Instituto de Radioastronomía y Astrofísica, Morelia, Mexico

In this talk I will show you a study on the detectability of the emission associated with the AGN dusty structure at sub-mm wavelengths using ALMA, in a theoretical and observational way. Theoretically, we use the Clumpy models from Nenkova et al. together with the mid-infrared to X-ray and the radio fundamental plane scaling relations. We find that it is more likely to detect bigger and denser dusty tori at the highest ALMA frequency (666 GHz/450 μm). Observationally, we use four prototypical AGN: NGC 1052, NGC 1068, NGC 3516, and IZw1, with radio, sub-millimeter, and mid-IR available data. We fit the mid-IR and radio spectra and we combined and extrapolated both fits to compare the extrapolation of both torus and jet contributors at sub-mm wavelengths. Our observational results are consistent with our theoretical results. The most promising candidate to detect the torus is the QSO IZw1 (therefore, highly accreting sources in general), although it cannot be resolved due to its large distance. We suggest that to explore the detection of a torus at sub-mm wavelengths, it is necessary to perform an SED analysis including radio data, with particular attention to the angular resolution.

Broadband radiometric searches for dark matter in radio to sub-millimeter regimes

Lunch Colloquium
Dr. Andrei P. Lobanov
ORATED
MPIfR

Prompted by the lack of detection of a massive dark matter carrier particle, the experimental scope of dark matter searches has been gradually shifting toward lower particle masses which correspond to frequencies below 1 THz. At these frequencies, weakly interacting sub-eV particles (WISP) are considered to be likely candidates for explaining the dark matter. Particularly promising in this regard are the QCD axions, axion-like particles (ALP), and hidden photons with masses between 0.1 micro-eV and 10 meV (24 MHz -- 2.4 THz frequency range). Searching for potential WISP dark matter signal in this entire frequency range requires making efficient, broadband radiometric measurements performed at a power sensitivity of better than 10^-23 W and a fractional spectral resolution of about 10^-6. The WISP Dark Matter eXperiment (WISPDMX), operated in collaboration between the MPIfR, University of Hamburg, and DESY, has pioneered such broadband radiometric searches and achieved the best exclusion limits for hidden photon dark matter in the 10-500 MHz (0.04-2.0 micro-eV) range. This effort is going to be further expanded with Broadband Radiometric Axion Seacrhes (BRASS) experiment which will enable WISP dark matter searches in the unprecedentedly broad, 20-1000 GHz frequency range. A review of the WISPDMX results and a summary of the BRASS activities will be presented in this talk.

Modified Gravity in Plane Sight

Special Colloquium
Dr. Indranil Banik
ORATED
Helmholtz-Institut für Strahlen- und Kernphysik

The satellite galaxies of the Milky Way and Andromeda mostly lie within thin (<20 kpc) planes. This strongly suggests a violent formation mechanism whereby galactic interactions(s) formed tidal tails from the outer disks of these galaxies. These tidal features could later coalesce into the observed satellite planes, a process known to occur and feasible in the ΛCDM standard cosmological paradigm (Newtonian gravity + dark matter). However, it implies that the satellites should be free of dark matter and thus have very low internal velocity dispersions, contrary to observations. Thus, I will present a reasonable model for the satellite galaxies using an empirical acceleration-based modification to gravity which can explain internal dynamics of galaxies without dark matter and in fact with very little freedom. In this theory (MOND), the Milky Way and Andromeda flew past each other ~9 Gyr ago, with most of their satellites forming from tidal debris during this interaction. In recently published MOND restricted N-body simulations of this flyby (MNRAS, 477, 4768), it is possible to reproduce the large-scale geometry of both satellite planes as well as the age and thickness of the Milky Way’s thick disk, an old structure which formed rapidly with an associated starburst around the expected time of the interaction. Some models can also get counter-rotating satellites around the Milky Way (analogues to Sculptor) but not around Andromeda, where there is no evidence for counter-rotators. I will finish with future work in this area and other possible tests of MOND.

Testing jet formation in a new sample of radio galaxies

Lunch Colloquium
Dr. Biagina Boccardi
ORATED
MPI für Radioastronomie & Osservatorio di astrofisica e scienza dello spazio di Bologna

In the recent years, radio galaxies proved to be the ideal targets for studies aimed at investigating the launching mechanism of relativistic jets. Inferring the intrinsic properties of the jet base through high-resolution radio observations is easier in misaligned objects than in blazars, due to the reduced impact of Doppler boosting and projection effects. So far, very-long-baseline interferometry studies of jet formation have been performed in selected nearby objects (mainly in M87, Cygnus A, and 3C84), and have provided important observational evidence in support of the magnetic launching models. In this talk, I will discuss the attempt to identify a larger sample of radio galaxies suited for such analyses, and I will present first results concerning the high-energy emission, the collimation properties, and the internal structure of the plasma flow in still unexplored sources down to scales of hundreds Schwarzschild radii.

The detection of leaking ionizing radiation from dwarf star-forming galaxies at redshifts 0.3 - 0.4

Lunch Colloquium
Dr. Y. I. Izotov
ORATED
Bogolyubov Institute for Theoretical Physics, Kyiv, Ukraine

Low-metallicity dwarf star-forming galaxies are often considered as the main sources contributing to the reionization of the Universe at redshifts 5-10. However, observations of these distant galaxies are difficult because of their intrinsic faintness. Instead, it was proposed to observe analogues of primeval galaxies at lower redshifts with higher apparent brightness aiming to detect leaking ionizing radiation at rest-frame wavelengths below the Lyman limit at 912 angstrom. I will present recent results of the spectroscopic observations of galaxies at redshifts 0.3 - 0.4 obtained with the Cosmics Origin Spectrograph (COS) onboard the Hubble Space Telescope (HST). It was found that all observed galaxies are leaking ionizing radiation. The escape fraction of this radiation in some galaxies is very high.

Black holes: portents for new gravitational physics

Special Colloquium
Prof. Steve Giddings
ORATED
University of California, Santa Barbara. USA

As evidence mounts for the existence of black holes, we have failed to give a satisfactory description of them in quantum theory, revealing an apparent contradiction among current foundational physical principles and indicating the need for their revision. One approach is to view black holes as quantum subsystems that can exchange information with their environment, making contact with problems in quantum information theory. The need to modify present physics also raises the question of observational tests, via gravitational or electromagnetic radiation from the near-horizon region.

Relativistic redshift of the star S0-2 orbiting the Galactic center supermassive black hole

Special Colloquium
Dr. Tuan Do
ORATED
UCLA, Los Angeles, USA

I will present a direct test of the Einstein equivalence principle around a supermassive black hole using the orbit of the Galactic center star, S0-2/S2. A key aspect of this experiment is the combination of our existing spectroscopic and astrometric measurements (1995-2017) that cover its 16-year orbit with new measurements in 2018 (March to September) that capture three key-observable events during its second measurable closest approach to the black hole. I will discuss the detection of the gravitational redshift on the orbit of S0-2 and the importance of systematic errors as measurements become increasingly more precise. I will also discuss the future of tests of gravity with stellar orbits at the Galactic center with the next generation of large ground-based telescopes such as the TMT and ELT.

Terahertz Airborne Astronomy using a Four Detector High Resolution Spectrometer: 4GREAT

Promotionskolloquium
Carlos A. Durán
ORATED
MPIfR

After the Herschel Space Telescope ceased operations in 2013, the astronomical community has been lacking access to those parts of the terahertz spectrum that are not visible from ground-based observatories. The atmosphere blocks most of the radiation at those frequency bands, even at high geographical altitude facilities like the Atacama desert (> 5000 m altitude), where APEX and ALMA operate. 4GREAT, an extension of the German Receiver at Terahertz frequencies (GREAT) operated aboard the Stratospheric Observatory for Infrared Astronomy (SOFIA), has been developed in response to those needs. This works describes its design, test, commissioning and scientific capabilities. 4GREAT is a heterodyne receiver that comprises four different detector bands and their associated subsystems, which can be simultaneously operated fully independently in one system. All four detector beams are co-aligned on the sky. The four frequency bands of 4GREAT cover 492-627, 893-1073, 1239-1515 and 2495-2690 GHz respectively. Various astrophysically important spectral lines are observable in each band, and in some cases different transitions of the same species, for example CO, lie in two or more bands of 4GREAT. The very important ground state transitions of various molecules can be observed, including NH3 , H218O, CH, OH, OH+ , NH, NH2, and the deuterated isotopologues HDO, and OD, as well as fine structure lines from neutral atomic carbon, [CI], and ionized nitrogen, [NII]. The expanded capabilities of GREAT with 4GREAT are now being used for a variety of spectroscopic studies. Its potential has been demonstrated by an absorption study of two ground state transitions or the methylidyne radical (CH) in diffuse molecular gas. As CH traces the unobservable molecular hydrogen, such observations are of fundamental importance for diffuse cloud astrochemistry. [Referees: Prof. Dr. Karl M. Menten, Prof. Dr. Frank Bertoldi, Prof. Dr. Ian Brock, Prof. Dr. Hubert Schorle]

TBD

Main Colloquium
Prof. Samaya Nissanke
CANCELED
GRAPPA, University of Amsterdam

TBD

Constraining galaxy and black hole mergers with pulsars

Lunch Colloquium
Dr. Siyuan Chen
ORATED
University of Birmingham

We have strong evidence that super massive black holes reside in the centre of most galaxies. Galaxies have also been observed to merge, consequently the super massive black holes should also form a binary and eventually merge. These super massive black hole binaries (SMBHBs) emit gravitational waves (GWs) as they spiral into each other. The superposition of all the GWs emitted by the cosmic population of SMBHBs form a gravitational wave background (GWB). This GWB affect the time of arrival (TOA) series of the radio signals from pulsars in a characteristic and correlated fashion. Pulsar Timing Arrays (PTAs) make use of this fact and aim to detect gravitational waves by precisely timing an array ofpulsars. One of the prime targets for PTAs is the GWB from a population of SMBHBs. SMBHBs have a strong relation with their host galaxies, in fact, we believe that SMBHBs are created via the merger of the host galaxies. Thus, the rate at which galaxies merge is related to the population of merging SMBHBs. The GWB frequency spectrum can be computed by integrating the emission of one single binary over the whole population. I will present a parametric model to compute the strength of the GWB from the population of SMBHBs in terms of astrophysical observables. These include the galaxy stellar mass function, pair fraction and merger time scale as well as the galaxy mass - black hole mass relation with scattering. All of which are interesting quantities, that have already been measured and constained. Using a PTA upper limit on the GWB, we can directly compare and combine the constraints on these astrophysical observables from electromagnetic observations with those from PTAs. I will present preliminary results with our nested sampling algorithm, showing how much (or little) PTAs can tell us about galaxy and black hole mergers.

Measuring Magnetic Fields Near and Far via the Zeeman Effect

Main Colloquium
Dr. Tim Robishaw
ORATED
Dominion Radio Astrophysical Observatory, Canada

The Zeeman effect is the only observational tool that allows us to directly measure the magnetic field strength and direction in the interstellar medium. We provide an overview of ongoing projects in which we are using the Zeeman splitting of the 21-cm line and the 18-cm hydroxyl (OH) transitions in order to probe astrophysical magnetic fields. We will highlight the first detection of extragalactic Zeeman splitting in the OH megamaser emission from starburst galaxies. Results will be shown from a southern survey of Zeeman splitting in OH masers in our Milky Way's spiral arms that suggest field reversals relative to the field directions probed by Faraday rotation. We will also discuss previous measurements of the Zeeman effect in Galactic 21-cm radio emission, some of the instrumental challenges involved in such measurements, and plans for a large-scale survey underway on the 64-m Parkes telescope and the 26-m John A. Galt Telescope at the Dominion Radio Astrophysical Observatory.

Resolving the jet collimation region in blazar Mrk 501

Special Colloquium
Dr. Shoko Koyama
ORATED
ASIAA, Taiwan

Probing detailed structure of the inner part of the relativistic jets is a fundamental issue for understanding jet launching and collimation mechanisms. High-resolution VLBI observations have revealed the clear limb-brightened structure and allowed to study the jet collimation profile and discriminate the jet foot point of the nearby radio galaxy M87. However, intensive studies have not been performed for blazars. Multi-frequency VLBI analysis have revealed parabolically collimated structure, from ~1000 to ~100000 Schwarzschild radii. We will discuss the origin of the relativistic jet, either black hole accretion flow or spinning black hole, and further compare the jet launching mechanism with the profile of M87. We will also present our future prospects with the Event Horizon Telescope observations.

Distribution, physical and chemical properties of cold gas around galaxies

Special Colloquium
Dr. Rajeshwari Dutta
ORATED
ESO, Garching

Understanding the physical conditions and volume filling factor of the cold neutral medium phase, which is closely related to the molecular phase, is essential to understand the processes through which gas gets converted to stars in galaxies. HI 21-cm absorption allows us to probe the thermal state of the HI gas as well as the parsec- to kpc-scale structures in the gas and relate them to the in-situ star formation. Using more than 400 hrs of GMRT and VLA observing time, we have conducted systematic HI 21-cm absorption surveys, both at low-z (z < 0.4) and at high-z (0.5 < z < 1.5). At low-z, we have used a galaxy-centric observational approach, i.e. we have used radio-loud quasars whose sightlines happen to pass through the gas disks/halos of nearby galaxies (referred as quasar-galaxy pairs) to probe gas up to 40 kpc around the galaxies. At high-z, where it is difficult to detect galaxies directly, we have used an absorption-centric approach, where we have searched for neutral gas associated with strong metal absorption line systems. Using the above two complementary techniques, we have studied the distribution of cold neutral gas around galaxies and its connection with the galaxy properties, and metal and dust content. The results from these studies will be presented in this talk.

Supercomputer simulations of the emergence of cosmic structures

Main Colloquium
Prof. Volker Springel
ORATED
Max-Planck-Institut für Astrophysik, Garching

Hydrodynamical simulations of galaxy formation have now reached sufficient physical fidelity to allow detailed predictions for their formation and evolution over cosmic time. I will review the foundations of this methodology and describe results from a recent effort to construct a new generation of structure formation models, the IllustrisTNG simulations. These numerical simulations achieve large enough volume to make accurate predictions for clustering on cosmologically relevant scales, while at the same time being able to compute detailed galaxy morphologies, the enrichment of diffuse gas with metals, or the amplification of magnetic fields during galaxy formation. They also support the notion that supermassive black holes are crucial for determining the final life stages of galaxies.

X-ray properties of optically-selected clusters in the Subaru HSC-SSP field

Special Colloquium
Prof. Naomi Ota
ORATED
Nara Womens University, Japan

I'd like to introduce our on-going project on X-ray follow-up observations of optically- and shear-selected clusters in the Subaru HSC survey, and report the status of XMM-Newton observations of massive galaxy clusters at 0.8 < z < 1.2 newly discovered in the HSC-SSP field. If time permits, I'd like to briefly show our Suzaku study of thermodynamical status of X-ray low surface brightness clusters in the local Universe.

Molecular complexity in the interstellar medium

Lunch Colloquium
Dr. Arnaud Belloche
ORATED
MPIfR

The search for complex organic molecules (COMs) in the interstellar medium (ISM) has revealed chemical species of ever greater complexity in various types of environment. This search relies heavily on the progress made in the laboratory to record and characterize their rotational spectra. Besides, our understanding of the chemical processes that lead to molecular complexity in the ISM builds on astrochemical numerical simulations that use chemical networks fed by laboratory and theoretical studies. On the observational side, the advent of the Atacama Large Millimeter/submillimeter Array (ALMA) and the expansion of the IRAM Plateau de Bure Interferometer now called NOEMA have recently opened a new door to explore the molecular complexity of the ISM. Thanks to the high angular resolution they can achieve, the spectral confusion of star-forming cores can be reduced, and their increased sensitivity allows astronomers to detect molecules of low abundance that could not be probed by previous generations of telescopes. The complexity of the molecules detected recently manifests itself not only in terms of number of their constituent atoms but also in their molecular structure. I will discuss results on molecular complexity in the ISM delivered by recent ALMA and NOEMA surveys.

The University of Tokyo Atacama Observatory 6.5m telescope

Special Colloquium
Prof. Mamoru Doi
ORATED
Institute of Astronomy, School of Science, University of Tokyo

The goal of the University of Tokyo Atacama Observatory (TAO) Project is to construct and operate a 6.5m infrared telescope at the summit of Cerro Chajnantor (altitude 5640m) in northern Chile. It is promoted by the Institute of Astronomy, School of Science, the University of Tokyo. The dry climate and high altitude provide excellent observation conditions from NIR to MIR wavelengths, as verified with the pathfinder 1-m telescope miniTAO. The 6.5m telescope has two Nasmyth foci where two facility instruments, SWIMS for the near-infrared and MIMIZUKU for the mid-infrared, will be installed, and two folded Cassegrain foci for carry-in instruments. The telescope, which includes three mirrors, is almost completed, and civil work at the site is underway. Two instruments are being commissioned at the Cassegrain focus of the 8.2m Subaru telescope on Mauna Kea, Hawaii. I will give an overview of the TAO project and present its current status.

What is Nature Astronomy and how to get published in it?

Special Colloquium
Dr. Marios Karouzos
ORATED
Nature Astronomy

Nature Astronomy, launched in January 2017, is a new research journal published by Springer Nature. Sitting alongside our sister journal Nature, we aim to publish high impact research in the fields of astronomy, astrophysics and planetary science. In this talk I will cover the motivation and scope of the journal, the types of manuscripts we publish, the editorial process and what we look for in papers. I will also cover common pitfalls of writing and submitting papers and I will share hints and tips on how to maximize the impact of your paper, from writing an engaging but informative title and a properly contextualized but concise abstract, to structuring your paper in a way that your results are communicated succinctly.

Millimetre VLBI Observations of M 87 and 3C 84

Lunch Colloquium
Dr. Jae-Young Kim
ORATED
MPI für Radioastronomie

I will present the results of a study of the innermost structure of the radio galaxies M 87 and 3C 84 performed with the global mm-VLBI array. Observations reach a resolution down to 7 gravitational radii in the case of M 87. For 3C 84, linearly polarized features were detected in the core region, with a large Faraday rotation in this region. These results constitute the main body from my PhD thesis, recently defended at the University of Cologne.

The European Open Science Cloud, EOSC-pilot, and the future of Open Science in Europe

Special Colloquium
Dr. Volker Beckmann
ORATED
CNRS, IN2P3, Paris, France

The European Open Science Cloud (EOSC) is a Horizon-Europe program, with the official launch of the EOSC in November 2018. The vision of this ambitious program is to provide to all researchers in Europe the access to data, services and computing infrastructures necessary to conduct their scientific projects. This Open Science vision is simultaneously embedded in national initiatives by governments of the EU member states. The EOSC-pilot is a 2-year preparatory project to evaluate possible business and governance models of the EOSC, to propose methods to reduce fragmentation and to improve interoperability between data infrastructures, and to develop a number of demonstrators functioning as high-profile pilots that integrate services and infrastructures to show interoperability and its benefits in a number of scientific domains. As the pilot comes to an end and the EOSC is going to go into its next phase, I will discuss the main pilot project results and the possible benefits and impacts of the EOSC on the way we conduct data and computing driven research in our domain.

The dawn of organic chemistry in space

Main Colloquium
Dr. Cecilia Ceccarelli
ORATED
UGA/IPAG, Grenoble

Since a long time, it has been known that molecular complexity in space can reach amazingly high levels. Alcohols, sugars and amino acids are detected in meteoritic and cometary material; some of them are even detected in regions where solar-like stars and planetary systems are forming today. These evidences led the Nobel prize laureate C.De Duve to affirm that the ''seeds of life are universal'' and that ''life is an obligatory manifestation of matter, written into the fabric of the Universe''. So far, the smallest seeds, which I will call here iCOMs (for interstellar Complex Organic Molecules), are detected in a bit more than a dozen solar-like star forming regions. New facilities, like IRAM/NOEMA and ALMA, are increasing this small number and providing images of these regions with unprecedented precision and sensibility. At the same time, new laboratory experiments and quantum chemistry theoretical studies suggest previously unpredicted routes of iCOMs synthesis. The combination of all these new works is challenging old theories and provoking the emergence of new ones. In this talk, I will present these recent advances and debates, and the new worldwide large projects whose goal is to unravel the dawn of organic chemistry in space.

VLBI and gamma-ray studies of TANAMI radio galaxies

Promotionskolloquium
Roberto Angioni
ORATED
MPI für Radioastronomie

I will report on the first systematic VLBI and gamma-ray monitoring study of a representative sample of radio galaxies with strong compact radio emission, with the aim of exploring the intrinsic relationship between high-energy emission and pc-scale jet properties in active galactic nuclei (AGN). While a number of studies have firmly established a close relationship between the gamma-ray and radio properties of AGN in general, the samples considered are dominated by blazars, i.e. AGN featuring well-aligned, Doppler-boosting-dominated jets. This poses a challenge in disentangling the orientation-dependent effects from the intrinsic emission produced in AGN jets. Radio galaxies, on the other hand, have misaligned jets whose emission is much less affected by Doppler boosting. We find that the high-energy emission in the compact jets of radio galaxies is not strongly driven by orientation-dependent Doppler boosting effects, much unlike the situation in their blazar counterparts. However, a significant correlation between gamma-ray flux and radio flux still holds, suggesting a direct physical link between the intrinsic emission properties of AGN jets in the two wavebands. We base our study on the decade(s)-long VLBI monitoring provided by the TANAMI and MOJAVE programs, in combination with gamma-ray data from Fermi-LAT, and also report on the interplay between pc-scale jet kinematics and gamma-ray emission in key individual sources.

The kiloparsec-scales of S5 0836+710 revisited by LOFAR

Special Colloquium
Prof. Dr. Manel Perucho
ORATED
Universitat de València, Spain

Recent LOFAR observations have changed our view on the kiloparsec-scale structure of this quasar. In this talk I will present the results from these observations, which show that the arcsecond bright region is not a disrupted relic, but a hotspot. Furthermore, we have been able to unveil the counter-hotspot, as a halo-like resolved feature around the core. I will develop on how this detection, together with stability analysis of the source, performed in a parallel work, has allowed us to determine physical parameters of the jet and also the intergalactic medium density around this z=2.2 source.

Reconstructing complex pulsar scattering environments with global VLBI

Special Colloquium
Dana Simard
ORATED
University of Toronto

Pulsar scintillation, the variation of the observed flux of a pulsar due to multi-path propagation, allows a glimpse into the small-scale plasma structures in the interstellar medium that scatter pulsar radiation - if we can infer their properties from the observed scintillation pattern. We have developed a model of scintillation from refractive plasma sheets that makes testable predictions which can be compared with observations to investigate these plasma structures. The main challenge in testing these models is mapping the scattered flux distribution of the pulsar on the sky, and to put physical scales to the constraints we must determine the scattering geometry of the system. I will discuss our novel interferometric technique to reconstruct the scattered flux of the pulsar and solve for the scattering geometry, even if the scattering environment is complex. This allows us to expand our study of pulsar scintillation to more systems and improve our global understanding of plasma scattering, which may benefit timing of millisecond pulsars and the aid in the interpretation of spectral structure in Fast Radio Bursts.

Space-VLBI studies of internal structure and physical processes in extragalactic relativistic jets

Promotionskolloquium
Laura Vega García
ORATED
MPIfR

In this talk I present the RadioAstron images of 4 sources: 3C 345, 1642+690, 0836+710, and 3C 273. I will then present the spectral analysis in the context of 0836+710. The core-shift analysis of this source hints at the presence of a recollimation shock. A kinematic analysis using the 43 GHz Boston University Blazar program data confirms the existence of a recollimation shock at a distance of 0.15 mas from the jet origin. We use the core-shift analysis and synchrotron spectrum fitting to estimate the magnetic field strength in the jet core, with both methods providing a consistent estimate of B_core ~ 0.04 G at 5 GHz. We also use the 1.6 GHz data (ground and space VLBI) to determine the ridgeline of the jet and use it for investigating the development of Kelvin-Helmholtz instabilities in the flow. We identify several distinct modes of the instability and determine their wavelengths and growth lengths. This study allows us to derive relevant physical parameters such as the jet classical jet Mach number and density ratio of the jet with respect to the ambient medium. We also perform a ridgeline analysis in 3C 273 that allows us to obtain the rotation speed of the jet. NOTE: The PhD Colloquium will be held at the Conference Room of the Institute of Theoretical Physics from the Faculty of Physics in Cologne, in the nearby building to the Physics Institute.

Testing General Relativity with Infrared Interferometry in the Center of the Milky Way

Main Colloquium
Prof. Reinhard Genzel
ORATED
MPE, Garching, Germany, and University of California, Berkeley, USA

The Center of our Galaxy is a unique laboratory for exploring the astrophysics around a massive black hole and testing General Relativity and other theoretical concepts in this extreme environment. I will discuss the results of a major campaign of observing the Galactic Center in 2017/2108 with three instruments at the European Southern Observatory's VLT, including the novel GRAVITY interferometric beam combiner of the 4 UTs. During this period the B-star S2 completed a peri-passage at ~1400 R_S, and permitted for the first time a test of the equivalence principle and the detection of the first post-Newtonian orbital elements in a classical 'clock experiment' around a massive black hole.

Finding the slowest pulsars

Master Colloquium
Jompoj Wongphecauxson
ORATED
MPIfR

Pulsars are remnants of intermediate mass stars (8-25 Solar mass) that emit electromagnetic radiation, mostly detected at radio frequencies. Pulsars are used as tools to study many physical phenomena, such as mapping the distribution of electrons in the interstellar medium. The methods used to search for pulsar that I am going to discuss are single pulse searching, the Fast Fourier Transform (FFT), and the Fast Folding Algorithm (FFA). Although the FFT has discovered the majority of pulsars, the FFT has some limitations, for example, detecting long-period pulsars (period longer than 1s). This limitation might cause us to miss some long period pulsars from the previous pulsar surveys which typically used the FFT. I will compare the FFT, FFA and single-pulse search efficacy. Radio frequency interference (RFI) affects the detectability of pulsars by creating numerous artificial pulsar candidates. In this work, I shall present a new method of RFI mitigation using over 70 million pulsar candidates detected in the FFT pipeline of the HTRU-N survey using Effelsberg telescope to identify periodically long live RFI. Pulsars in binary systems are affected by the motion, causing a Doppler shift which changes in their apparent period smearing and reducing the S/N of pulse profiles. A straightforward way to reduce this period change, called acceleration searching, which consists of assuming a constant acceleration and re-sampling the time series. I created acceleration-FFA pipeline for this thesis as well as an optimisation of the acceleration step size. Using the acceleration-FFA pipeline, I have processed 122 observations from the HTRU-S low-lat observed with Parkes telescope. Three new pulsar candidates have been discovered from this pipeline. Our method also redetected a pulsar that had been overlooked previously by the FFT pipeline. Finally, I also confirmed a FAST telescope pulsar candidate. [Referees: Prof. Dr. Michael Kramer, Prof. Dr. Norbert Langer]

Cold outflows ruffling AGN host galaxies

Main Colloquium
Dr. Claudia Cicone
ORATED
INAF - Osservatorio Astronomico di Brera

There are several lines of evidence for the presence of multiphase outflows ruffling the ISM of AGN host galaxies. Observations of massive and fast outflows of molecular gas, extending by several kpc, suggest that the feedback from powerful AGNs can undermine even the coldest and densest phase of the ISM that directly fuels star formation. However, because of our limited knowledge of the physical conditions of the outflowing molecular gas, the outflow energetics estimates are affected by large uncertainties. In an effort to advance in this field, we performed ALMA+ACA observations of NGC6240, a nearby IR-luminous galaxy merger hosting two AGNs in its nucleus. These data reveal that the molecular outflow extends by more than 10 kpc, and that - quite puzzlingly - its emission peaks between the two AGNs (rather than on either of the two). Furthermore, by combining the information from Carbon Monoxide (CO) and Carbon (CI) emission line data, we inferred an alpha_CO conversion factor of ~2 MSun/(K km/s pc^2) for the outflowing gas. This is lower than the alpha_CO derived for the non-outflowing medium (alpha_CO~3), but it is still large enough to guarantee that the outflow entrains a significant fraction of the molecular ISM, which we estimate to be 60+-20% within the central ~5 kpc. I will discuss these findings in the context of our understanding of the ISM properties of (U)LIRGs and of the feedback mechanisms shaping galaxies across cosmic times.

Young Stellar Objects in the Central Molecular Zone

Master Colloquium
Alya Amirah Azman
ORATED
MPIfR

The Galactic Center (GC) environment provides unique and extreme conditions for star formation within the Milky Way. Candidate young stellar objects (YSOc) in the GC have previously been identified using Spitzer 24 micron emission. Star formation rates determined directly from YSOs counts are much higher than the value estimated from other methods. In addition, the YSOc distribution shows a puzzling asymmtery such that they are preferentially located at negative Galactic longitudes, while the molecular gas distribution is mostly concentrated to positive longitudes. To resolve the nature of these YSOc, we have conducted spectral line observations of these sources with APEX at 230GHz and characterized the dense gas associated with them. We also examine the far-infrared and submm properties of the YSOc using Hi-GAL and ATLASGAL survey data. Furthermore, using 70 micron data from Herschel Hi-GAL survey, we produce an independent catalog of YSOc. These confirm the known sites of star formation, as well as reveal new ones. Interestingly, based on our spectral line and dust continuum analysis, we find no evidence for the previously reported asymmetry. We conclude that some previous YSO catalogues were likely biased by contaminants, resulting in biased estimates of the star formation rate and its spatial distribution in the GC. [Referees: Prof. Dr. Karl Menten, Priv.-Doz. Dr. Maria Massi]

Prospects of testing alternative theories of gravity with Pulsar-White Dwarf binaries

Master Colloquium
Georgios Lampropoulos
ORATED
MPIfR

Alternative theories of gravity, in contrast to general relativity (GR) generally predict an additional dipolar term of gravitational radiation, an effect which becomes particularly strong in asymmetric binary systems. For that reason, dipolar radiation should modify the intrinsic orbital period derivative of that systems. Pulsars with White Dwarf companions (PSR-WD) so far turned out to be the best laboratories for constraining dipolar radiation. In this thesis, I focused on four essential relativistic PSR-WD laboratories characterised by low eccentricities and short orbital periods: PSR J1012+5307, PSR J1738+0333, PSR J1909-3744 and PSR J2222-0137. For these PSRs I have conducted extensive mock timing data simulations until 2030 for two different scenarios: Considering new and upcoming telescopes (FAST, MeerKat and SKA1) and considering only telescopes have so far been used (Arecibo, Effelsberg, Nancay etc.). In both cases, I investigate the improvement of the precision of the Post Keplerian parameters. A discussion about the limitations on these systems coming from insufficient mass or distance measurements and contributions due to the Galactic potential or Shklofskii effect will be carried out. Based on the mock data simulations, I will also present generic limits on dipolar gravitational radiation and how they will improve over the next decade. Furthermore, I will make a comparison with other types of experiments like the constraints obtained by the test of the universality of free fall in the triple system PSR J0337+1715. This comparison will be made within Jordan-Fierz-Brans-Dicke (JFBD) scalar-tensor theory of gravity. [Referees: Prof. Dr. Michael Kramer, Prof. Dr. Pavel Kroupa]

The CHIME/FRB and Pulsar projects

Main Colloquium
Dr. Cherry Ng
ORATED
Dunlap Institute for Astronomy and Astrophysics, University of Toronto, Canada

The Canadian CHIME telescope (the Canadian Hydrogen Intensity Mapping Experiment) located in Penticton, Canada BC, has recently come online and obtained first light observations. Originally designed as a cosmology instrument, it was soon recognized that CHIME has the potential to simultaneously serve as a great radio telescope for Fast Radio Bursts (FRBs) and pulsar science. CHIME operates across a wide bandwidth of 400 - 800 MHz and has a collecting area and sensitivity equivalent to that of the world’s largest radio telescopes. A high FRB survey efficiency is expected, with an estimated discovery rate of a few FRBs per day, thanks to the 1024 independent beams covering ~200 square degrees on sky and a real-time detection pipeline. The commensal pulsar backend is instead capable of tracking 10 pulsars simultaneously at any one time, 24-hrs per day, every day. We plan to carry out daily monitoring of all NANOGrav pulsars employed in Pulsar Timing Array work, and can cycle through all pulsars in the northern hemisphere within roughly a 10-day cadence. In this talk, I will present the latest progress of the CHIME/FRB and pulsar projects.

Half Century of my Astronomy - from a Star to Galaxies

Main Colloquium
Prof. Keiichi Kodaira
ORATED
Japan Society for the Promotion of Science (JSPS)

Towards the end of 10-years stay in Bonn as JSPS-Bonn Director and lucky visitor to MPIfR Colloquium, my astrophysicist career will be reviewed, how my thesis work on a star at CAU Kiel in 1964 led to Research Fellowship of CALTECH (1967-69), and to my own project Quantitative Classification of Galaxies in 1980s. Some of the background episodes in realizing the Japanese Large Telescope Project SUBAU in Hawaii (1980-1999) will be disclosed, being followed by the story about the collaboration with Prof. Vansevicius of the Vilnius Observatory in searching for Missing-Link Star-Clusters in M31 using the SUBARU images (2000-2009). I will report the recent development of Dynamical Classification of Galaxies using CALIFA data, to which I have been committed since a few years in collaboration with Dr. Kalinova at MPIfR. Finally, JSPS Postdoctoral- and Invitation-Fellowship Programs are briefly introduced.

A study of pulsar J1903+0327 as a laboratory for fundamental physics

Master Colloquium
Franziska Heusgen
ORATED
MPIfR

Pulsars are rapidly rotating, strongly magnetised neutron stars observed as sources with periodic signals most often in the radio spectrum which can be used to study a wide variety of physical phenomena. Due to their high rotational stability, especially binary pulsars are ideal testbeds for gravitational theories such as General Relativity. The aim of this master thesis is to perform an in-depth study of PSR J1903+0327, a millisecond pulsar in an eccentric, wide orbit with a main-sequence star as companion that is observed with various radio telescopes since 10 years. In this thesis, we analyse the observations from the last 6 years taken with the Arecibo radio telescope and improve the previous found timing solution by including our data. With our results, we are able to test different gravitational theories. General relativity predicts in contrast to most alternative theories of gravity the universality of free fall also for self-gravitating bodies. We constrain a new limit on a possible difference in the acceleration between PSR J1903+0327 and its companion star in the gravitational field of our Galaxy. By determining the intrinsic orbital period decay of the system, we derive limits on a possible time variation of the gravitational constant expected for many alternative theories of gravity. [Referees: Prof. Dr. Michael Kramer, Prof. Dr. Norbert Langer]

High-mass X-ray Binaries in the Fundamental Plane of Black Hole Activity

Master Colloquium
Staicy Stadtler
ORATED
MPIfR

The fundamental plane of black hole activity is the observed relationship between radio- and X-ray luminosities in accreting black holes, holding from stellar-mass black holes to supermassive black holes. Concerning accreting stellar mass black holes there exists a thorough analysis only for low-mass X-ray binaries (LMXBs). Our aim is to extend the study by including all known high-mass X-ray binaries (HMXBs) hosting a candidate black hole. Several archives are collected from the literature and incorporated into the analysis. Three archives consisting of LMXBs have been combined, HMXBs and two AGN archives have been added. We show that when the sample is analysed with the X-ray- and radio luminosity scaled with the Eddington luminosity all LMXBs and AGN cluster into two clear different regions whereas most of the HMXBs overlap with the AGN. We discuss three possible physical mechanisms at the basis of the found distribution: Doppler boosting, the accretion mechanism and the spectral state of the source. [First Advisor: Priv.-Doz. Dr. Maria Massi; Second Advisor: Prof. Dr. Karl M. Menten]

Multi-messenger Astronomy with Cosmic Neutrinos

Main Colloquium
Dr. Anna Franckowiak
ORATED
DESY, Zeuthen

The recent discovery of high-energy astrophysical neutrinos has opened a new window to the Universe. Identifying the sources of those neutrinos isthe most pressing question in the new field of neutrino astronomy. Combining neutrino data with electromagnetic measurements in a multi-messenger approach increases the sensitivity to identify the neutrino sources and helps to solve long-standing problems in astrophysics such as the origin of cosmic rays. A first compelling candidate was identified on September 22, 2017, when the IceCube Neutrino Observatory observed an extremely high-energy neutrino, IceCube-170922, in spatial and temporal coincidence with a gamma-ray flaring blazar, TXS 0506+056, monitored by the Fermi Large Area Telescope. The coincidence triggered a large follow-up campaign in a broad wavelength band. In this talk I will review the recent progress in multi-messenger astronomy using neutrino data with a focus on the candidate source, TXS 0506+056.

Cosmology vs. Phase-Space Correlations in Systems of Satellite Galaxies

Special Colloquium
Dr. Marcel Pawlowski
ORATED
Hubble Fellow, University of California, Irvine

In the Local Group and nearby Universe, several types of phase-space structures have been found, some of which are in tension with expectations based on the ΛCDM model of cosmology. The most prominent among these is the Planes of Satellite Galaxies problem, while others such as the overabundance of satellite galaxy pairs, the excess of backsplash galaxies, and the lopsidedness of satellite galaxy systems have thus far received less attention. These issues show that the mutual distributions and motions of satellite galaxies are powerful tests of cosmological models, due to the limited dependency of the positions and motions of satellite galaxies on the exact modeling of baryonic processes. I will review the current status - and possible interdependence - of these types of phase-space correlations, with an emphasis on the Milky Way system and the cosmological implications of our Gaia DR2 proper motion measurements for the majority of its satellite galaxies.

High energy neutrinos from merging black holes such as blazars

Lunch Colloquium
Prof. Dr. Peter L. Biermann
ORATED
MPI für Radioastronomie

High energy (HE) neutrinos are expected from interaction of high energy protons and nuclei. (A) Here we review first the sources of high energy protons and nuclei: i) Blue Super Giant star (BSG) supernovae exploding into their own wind give about $3 \cdot 10^{17} \, Z$ eV. ii) Gamma Ray Bursts (GRBs) can give a factor of a few hundred more energy per particle. iii) Radio galaxies can yield a few $10^{20}$ eV, and iv) blazars, basically radio galaxies with their relativistic jet pointed at us may reach the same energy. The cut-off spectra of hot spots in radio lobes, radio jet knots and compact nuclei of AGN, and the double-hump spectrum of blazars can all be understood with this approach: all present observational evidence for the presence of ultra high energy particles (UHECRs). (B) Second we review the source 41.9+58 in the starburst galaxy M82: It may be a mis-directed Gamma Ray Burst resulting from the merger of two stellar mass black holes: The open conal structure around it can be interpreted as resulting from the conal sweep of the dominant jet during a spin-flip. This in turn is caused by the orbital spin winning over intrinsic spin. 41.9+58 can be expected to have produced ultra high energy protons (perhaps also nuclei), high energy gammas, high energy neutrinos, and gravitational waves. (C) Third we consider the neutrino events of IceCube. Six of these events can be associated with relativistic jets pointing at us from blazars; one of them shows evidence for several neutrino events (TXS 0506+056 = PMN J0509+0541), and also coincident $\gamma$-ray flaring, while the other events are too old to allow a full check in the earlier data. All of these six sources allow interpretation as an ongoing merger of two super-massive black holes with an associated spin-flip; interaction is increased while the dominant jet sweeps around, allowing strong injection, acceleration and interaction. So flat radio spectra extending to far beyond GHz can be understood, very high energy protons and nuclei, high energy gammas and neutrinos, and in the actual merger gravitational waves. Future observations at IceCube and other observatories will check this picture. As the particle energies go much higher than at CERN, we can hope for new discoveries.

The upgraded GMRT: Opening more wavebands for the Universe

Special Colloquium
Prof. Dharam Vir Lal
ORATED
NCRA, Tata Institute of Fundamental Research, Pune, India

The Giant Metrewave Radio Telescope (GMRT) has just completed a major upgrade. The upgraded GMRT significantly improves scientific capabilities and allow GMRT to retain its status as the most sensitive radio interferometers in the world at low, less than 1 GHz frequencies. The main feature of the upgrade is near-seamless frequency coverage over 125-1450 MHz band. In the talk, I would present several more features of the upgrade and the science results that we obtained from it.

Dissecting the AGN disk-jet system with joint VLBI-Gaia analysis

Lunch Colloquium
Prof. Dr. Yuri Y. Kovalev
ORATED
Astro Space Center of Lebedev Phys. Inst. & Moscow Inst. of Phys. and Technology, Moscow, Russia

We analyze the positions of active galactic nuclei measured by VLBI and Gaia Data release 2 and compare the found significant VLBI-Gaia offsets in more than 1000 AGNs with their jet directions and colors. Exciting results for the whole sample as well as separate AGN classes will be presented.

The Cool Side of Galactic Winds

Main Colloquium
Prof. Sylvain Veilleux
ORATED
University of Maryland, USA

Galactic winds impact ongoing star formation and black hole activity in their hosts and deposit mass and energy into their halos and the intergalactic medium. Major outstanding questions remain, however, about the precise impact of these galactic winds on their surroundings. In particular, the exact nature of the neutral and molecular gas phases in these winds is still unclear. This colloquium will highlight the recent discovery of powerful atomic and molecular winds in nearby galaxies and quantify the role of AGN/quasars in driving these winds.

Low frequency radio telescopes: LOFAR and SKA paths to 2020

Main Colloquium
Prof. Carole Jackson
ORATED
General and Scientific Director ASTRON, the Netherlands

LOFAR has matured into a powerful low frequency telescope capable of a wide range of astronomical capabilities. In this update I will summarise the development of LOFAR into the International LOFAR telescope, and our future vision - a future tightly bound to the mission of ASTRON, our ILT partners, and the realization of the global SKA telescope.

The production of dust in galaxies

Main Colloquium
Dr. Francisca Kemper
ORATED
Academia Sinica, Institute of Astronomy and Astrophysics, Taiwan

The evolution of interstellar dust reservoirs, and the evolution of galaxies themselves go hand-in-hand, as the presence of dust alters evolutionary drivers, such as the interstellar radiation field and the star formation history, while at the same time, the dust is being formed and altered by processes taking place in galaxies. Indeed, dust can often even be used as a tracer of physical conditions. The exact mineralogical composition, the size and the shape of dust grains, are all affected by the physical conditions. Due to the more permanent nature of solids, dust grains provide a historical record of its processing history, while interstellar gas will only ever probe the present conditions. I will discuss our recent results on the Magellanic Clouds, Local Group galaxies, the Milky Way, AGN tori, and starburst galaxies, and highlight future observational opportunities open to astronomers to continue the study of interstellar dust in galaxies.

Mid- and high-J CO observations towards massive star forming clumps

Master Colloquium
Thanh Dat Hoang
ORATED
MPIfR

The success of ATLASGAL which is the first large scale unbiased survey looking for high mass star formation sites in the inner part of the Milky Way and the selection of its TOP100 sample lead to various follow-up studies on the physical and chemical properties of different evolutionary stages of high mass star formation in our Galaxy. In this talk, the observations of three mid- and high-J CO transitions, 13CO(6-5), C18O(6-5), and 13CO(10-9) toward the TOP100 sample using the APEX telescope and the Herschel Space Observatory will be presented. The TOP100 sources are classified into four sub-groups, 70 μm weak (70w), mid-Infrared weak (IRw), mid-Infrared bright (IRb), and HII regions, that represent four evolutionary stages of high mass star formation in the order of time, respectively. The CO lines have been detected in all the groups except for the 13CO(10-9) line in the 70w group. Detection rates get higher towards the more evolved groups, up to 100% for all three lines in the HII regions group. The line width and intensity are found to become broader and higher toward late phases of star formation due to the presence of a more dynamic environment and heating sources that reduce the CO depletion. The size of the 13CO(6-5) emission is estimated and is usually less than the size of the dust continuum emission measured by ATLASGAL. The 13CO(6-5) is also determined that it originates from either cores of cold clumps or from the PDRs. The high-J CO lines show narrower line widths and lower intensities compare to the mid-J CO lines. The integrated intensities of low- to high-J CO transitions show good correlations with the L/M ratio suggesting that they can be the indicators for the evolutionary sequence of high mass star formation. The 13CO(6-5) optical depth, excitation temperature, and 13CO column density have been calculated under local thermodynamic equilibrium (LTE). The results range from 0.15 to 2.47, 20 to 120 K, and 10^15 to 10^17 cm^-2, respectively. We used the RADEX program to model the 13CO(6-5) and 13CO(10-9) emission under non-LTE condition. The results put a lower limit on the Hydrogen density of 10^5 cm^-3 for the sources in the TOP100 sample. The 13CO(10-9)/13CO(6-5) ratio is found getting higher towards the more evolved sources, indicating an increase in the pressure inside the clumps. [Referees: Karl Menten, Pavel Kroupa]

Gravitational wave astrophysics at low frequencies

Main Colloquium
Dr. Enrico Barausse
ORATED
Institut d'Astrophysique de Paris/CNRS

I will review the status of the space-based Laser Interferometer Space Antenna (LISA) and its science goals. LISA will detect gravitational waves in the frequency range 10^-4 Hz to 1 Hz, a region of the spectrum populated by a large variety of astrophysical sources. Among these, a major role will be played by the mergers of massive black holes, which LISA will detect up to very large redshift z = 10-20. I will focus on the physics of these sources, as well as on how their detection by LISA will shape our understanding of astrophysics, cosmology and fundamental physics.

The gravitational-wave sky so far

Main Colloquium
Prof. Alberto Vecchio
ORATED
University of Birmingham

In less than two years of operation, gravitational-wave observatories - Advanced LIGO, and more recently Virgo - have directly detected gravitational waves, discovered binary black hole mergers, revealing an abundant population of these systems, and observed the first binary neutron star coalescence. The aftermath of this event was also observed across the electro-magnetic spectrum, from gamma rays to radio waves, providing evidence that binary neutron star mergers are engines behind (at least some) short gamma ray bursts and primary production sites of elements heavier than iron in the Universe. I will summarise the results so far, their main implications and touch upon prospects for the future.

Neutral hydrogen in spiral galaxies, gas accretion, and the MeerKAT

Special Colloquium
Dr. Gyula I. G. Józsa
ORATED
South African Radio Astronomy Observatory and Rhodes University

Spiral galaxies are building stars on larger time scales than the depletion time of the gas available in the galaxies themselves. Hence, a replenishment of the star formation reservoirs has to be supplied from the environment. But how this happens in detail is not well known. In the recent years, the question of how galaxies compensate their gas losses through star formation has been targeted by observing also the neutral hydrogen component of galaxies. In this talk I will discuss some recent findings from HI observations in the context of gas accretion and describe how future radio telescopes will help to shed more light into the nature of this process. In particular I will focus on the Karoo Array Telescope, MeerKAT, a new radio interferometer in the Karoo desert in South Africa.

Study of nearby spiral galaxies at low frequency

Master Colloquium
Ayushi Mandlik
ORATED
MPIfR

This thesis presents the first arcsec resolution observations of two nearby spiral galaxies- IC 342 and NGC 628, using Low Frequency ARray (LOFAR). Low frequency (145 MHz) continuum observations trace older, lower-energy cosmic-ray electrons in the galaxy via radio synchrotron emission. These electrons are ones that have travelled away from their locations of origin (supernova remnants) and are present in the extended disks and haloes of the galaxies. Low frequency surveys also help us understand the properties of warm ionized mediums of galaxies with the help of free-free absorption of synchrotron flux density by the ionized gas. The first part of my thesis presents FACTOR, which is the novel algorithm used to calibrate and image the galaxies using LOFAR visibilities. Images of the two face-on star forming spiral galaxies are presented at various resolutions. This is followed by an analysis of the spectral index distribution in the galaxies obtained between the LOFAR maps and VLA1 maps of 1.49 GHz for IC 342 and 3 GHz for NGC 628. Correlations between spectral index values and the levels of star formation are obtained with the help of far-infrared, H-alpha and thermal radio emission maps, which trace the regions of star formation in galaxies. Thermal fractions required to explain the observed spectral indices are calculated. The values of thermal fraction needed to explain the flat spectral index values seen in the central part and arms of IC 342 seem unphysical. This leads to the explanation that IC 342 suffers from higher levels of thermal absorption due to higher star formation rates. On the other hand, NGC 628 does not seem to suffer much from thermal absorption owing to its lower levels of star formation. Low frequency observations are also ideal to study diffuse magnetic fields in galaxies. The technique of RM Synthesis is applied to obtain the parallel component of magnetic fields (while its perpendicular counterpart can be calculated from the synchrotron flux density). As a result of wavelength dependent Faraday depolarization, diffuse polarized emission cannot be detected for either of the two galaxies. [Referees: Prof. Dr. Michael Kramer, Prof. Dr. Cristiano Porciani]

ATLASGAL/SEDIGISM: Our Developing View of Star Formation in the Milky Way

Main Colloquium
Dr. James Urquhart
ORATED
University of Kent, UK

APEX is playing a pivotal role in surveying large fractions of the Galactic plane in both dense material traced by thermal dust emission and the large-scale diffuse gas traced by the 13CO (2-1) transitions. Combining these two surveys allows us to connect the massive, high density, compact clumps where stars are forming to their host giant molecular clouds and the larger scale features of the Galaxy (e.g., the spiral arms and Galactic bar). In this talk, I will discuss the impact these surveys are having to our understanding of the structure of the Milky Way, and the role different environmental conditions play in the star formation process.

Final results of Hitomi, and beyond

Special Colloquium
Dr. Liyi Gu
ORATED
Univ. of Tokyo, Japan

The X-ray micro-calorimeter on board Hitomi was the first instrument to achieve broad-band, high-resolution spectroscopic measurement of hot astrophysical plasmas. It was discovered with the Hitomi observation of the Perseus galaxy cluster that the gas velocity in the cool core region is 150-200 km/s, which is much slower than the sound speed; the abundances of eight different elements are accurately measured, revealing an enrichment pattern that is surprisingly identical to the proto-solar nebula. The results of Hitomi also uncovered that our knowledge of basic atomic physics is not enough for a full and precise understanding of the physical state of cosmic plasmas. The re-build of Hitomi, the XARM (launch 2022), has already started in international collaboration of JAXA, NASA, ESA, and others. XARM inherits the main scientific goal of Hitomi, to reveal material circulation and energy transfer in cosmic plasmas with high-resolution spectroscopy. The XARM spectroscopy will not be just refinement, but a qualitative leap in the astrophysics of structure formation and cosmic matter flow, as well as in the basic atomic and plasma physics.

Global Millimeter VLBI Array Survey of Ultracompact Extragalactic Radio Sources at 86 GHz

Lunch Colloquium
Dr. Dhanya G. Nair
ORATED
MPI für Radioastronomie

We present results from a large global 86 GHz VLBI survey of 162 compact radio sources conducted in 2010–2011 using the Global Millimeter VLBI Array (GMVA). For 138 objects, the survey provides the first ever VLBI images made at 86 GHz. The survey data are applied for studying jet physics down to smallest angular (approx. 50 microarcseconds) and linear scales. Brightness temperature measurements made from the survey data have been applied to estimate the intrinsic brightness temperature at the jet base (VLBI core) and in the nearest moving jet components. These measurements have been modelled by a basic population scenario with a constant Lorentz factor for the entire source sample. From this modelling, the core brightness is found to be limited by the inverse Compton losses, while equipartition and adiabatic expansion govern the observed evolution of the moving jet components. Combining the survey estimates of brightness temperature with data obtained at lower frequencies, we have also studied jet acceleration on scales of approx. 100-10000 gravitational radii, showing that an MHD mechanism is most likely responsible for accelerating the jet plasma on these scales.

The Intertwined Stories of Globular Clusters and their Black Holes

Special Colloquium
Dr. Sourav Chatterjee
ORATED
Tata Institute of Fundamental Research, Mumbai, India

Dense and massive star clusters such as the globular clusters (GCs) are efficient factories for stellar exotica including GW sources similar to those detected by LIGO and Virgo. I will describe the BBH formation process inside typical GCs and its implications, and discuss why GCs are so efficient in producing short-period binary black holes (BBHs). I will further show how the fates of a GC and its black holes are intimately connected making the retention fraction of BHs in today's GCs very interesting. I will describe the challenges for observationally constraining the retention fraction of BHs in today's GCs and possible ways to overcome them. One common uncertainty in predicting the rate of GW detections comes from the lack of constraints on the distribution of natal kicks for BHs. I will describe how this uncertainty could be alleviated with the help of GAIA.

Star Formation and Galactic Environment

Main Colloquium
Dr. Eva Schinnerer
ORATED
MPIA Heidelberg

High angular resolution observations of nearby galaxies allow us to sample the star formation process in different galactic environments. This provides insights on the importance and role of galactic components such as bulges, stellar bars, spiral arms and active galactic nuclei (AGN) in the conversion of cold (molecular) gas into stars. New instruments can now regularly image with high quality and sensitivity large field-of-views at the scale of individual star-forming units, namely Giant Molecular Clouds (GMCs) and HII region (complexes): ALMA is fundamental for imaging of the molecular gas properties in the star-forming disks, while the optical Integral Field Unit MUSE on the VLT is providing detailed information on the ionised gas and stellar population. I will highlight recent progress in the field and present new results from the Physics at High Angular resolution in Nearby GalaxieS (PHANGS) survey that studies a representative sample of nearby massive, normal star-forming galaxies.

The dawn of organic chemistry

Main Colloquium
Dr. Cecilia Ceccarelli
CANCELED
UGA/IPAG, Grenoble

TBD

The Cosmic Infrared Background as seen by Planck: New Insights into the CIB-CMB Lensing Cross Correlation

Lunch Colloquium
Dr. Daniel Lenz
ORATED
Jet Propulsion Laboratory, NASA, USA

The cosmic infrared background (CIB) is a powerful probe of large-scale structure across a very large redshift range, consisting of unresolved FIR emission from dusty galaxies. It can be used to study the astrophysics of galaxies, the star formation history of the Universe, and the connection between dark and luminous matter. The major difficulty here lies in obtaining accurate and unbiased large-scale CIB images that are cleaned from the contamination by Galactic dust. We used data of neutral atomic hydrogen from the recently-release HI4PI Survey to create template maps of Galactic dust, allowing us to remove this component from the Planck intensity maps. I will present our final CIB maps and the various processing- and validation steps that we have performed to ensure the high quality of these maps. Based on these new CIB maps, I will also present a cross correlation analysis of the CIB signal and the Planck CMB lensing map, which can be used to study the primordial non-Gaussianity through a scale-dependent bias term. Aside from this particular application, the soon-to-be public maps will enable the community to investigate a wide range of questions, related to the Universe's large-scale structure.

Ionized and photodissociation regions toward a new sample of massive star-forming clumps

Promotionskolloquium
Wonju Kim
ORATED
MPIfR

Ionized hydrogen (HII) regions are an excellent indicator of high-mass star-forming regions and ongoing star formation in galaxies. Powerful outflows from O/B stars in their early stages and, throughout their whole life, intense ultraviolet (UV) radiation and stellar winds appreciably alter the chemical composition of the ISM in their vicinity and turn the surfaces of molecular clouds into photodissociation regions (PDRs). To investigate the feedback of young high-mass stars on their environment, 967 high-mass star-forming clumps were targeted, which were identified by the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL). I will present two studies of HII regions and PDRs associated with high-mass star-forming clumps. The first study focuses on an extensive survey of HII regions using (sub)millimeter hydrogen radio recombination lines (submm-/mm-RRLs) observed with the IRAM 30m, Mopra 22m, and APEX 12m telescopes. This survey covers the largest sample of (sub)mm-RRL detection published to date. The RRLs show association with young HII regions and molecular clumps and provide unique velocity information of ionized gas associated with dust clumps. By using RRLs, we also determined electron densities of the HII regions (10^3 cm-3 < electron density < 10^5 cm-3). Moreover, we found the production rate of ionizing photons estimated by RRLs can be excellent measure as well as Lyman photon fluxes of radio continuum emission. In the second part, I will present the IRAM 30m observations of eight molecular tracers of PDRs, namely HCO, HOC+, C2H, cyclic-C3H2, CN, H13CN, HC15N, and HN13C as well as C18O and H13CO+. Some of the molecules (HCO, C2H, and cyclic-C3H2) show correlations of their column densities and abundances with the presence of HII regions. The correlations possibly imply that the abundances of molecules vary in molecular clumps including different circumstances. [Referees: Prof. Dr. Karl M. Menten (Max-Planck-Institut für Radioastronomie), Prof. Dr. Pavel Kroupa (Argelander-Institut für Astronomie), Prof. Dr. Klaus Desch (Physikalisches Institut), Prof. Dr. Hubert Schorle (Institut für Pathologie)]

Innovative Pulsar Searching Techniques

Promotionskolloquium
Andrew Cameron
ORATED
MPIfR

Pulsars, rapidly-rotating and highly magnetised neutron stars, can be utilised as tools in the study of many fundamental physical questions, most notably in the application of binary pulsars to the study of gravitational theories such as General Relativity. The discovery of ever-more relativistic binary systems than those presently known will allow for such tests to probe even deeper into the nature of gravity. Here, I will present results from the processing of 44% of the the HTRU-South Low Latitude pulsar survey, the most sensitive blind survey of the southern Galactic plane taken to date. This includes the discovery and long-term timing of 40 new radio pulsars identified through the continued application of a novel ''partially-coherent segmented acceleration search'' technique, which was specifically designed to discover highly-relativistic binary systems. These pulsars display a range of scientifically-interesting behaviours including glitching, pulse-nulling and binary motion, and appear to comprise a population of generally older, lower-luminosity pulsars as compared to the previously-known population. In addition, I will also present an in-depth study of PSR J1757-1854, the only relativistic binary pulsar to have been discovered in the HTRU-S Low Latitude survey to date. This extreme binary system promises to provide new insights into gravitational theories within the coming years. Finally, I will also present the results of a study into the Fast Folding Algorithm, a time-based pulsar searching technique which may overcome biases in the dominant Fast Fourier Transform search technique against long-period pulsars and the presence of low-frequency red noise. [Referees: Prof. Dr. Michael Kramer (MPIfR), Prof. Dr. Norbert Langer (AIfA), Prof. Dr. Klaus Desch (Physikalisches Institut, Univ. of Bonn), Prof. Dr. Karl Wagner (Pharmazeutische Technologie und Biopharmazie)]

Mapping Hot Gas in the Universe using the Sunyaev-Zeldovich effect

Main Colloquium
Prof. Eiichiro Komatsu
CANCELED
Max-Planck-Institut für Astrophysik, Garching

Hot, thermal electrons in galaxy clusters up-scatter the cosmic microwave background photons, making clusters visible in the microwave sky. This effect, known as the Sunyaev-Zeldovich effect, has been detected routinely toward individual galaxy clusters. Since the SZ effect is proportional to a projected thermal pressure of gas, we can use this effect to map all hot gas pressure in the Universe in projection. We start this talk by presenting the first image of the SZ effect obtained by ALMA, which has the highest spatial (both angular and physical) resolution ever achieved for the SZ mapping observations. With such a high resolution map comparable to X-ray maps, this SZ map enables us to study astrophysics of galaxy clusters in a new way. The second part of the talk concerns a full-sky map of the SZ effect. Thanks to its multi-frequency coverage from space, ESA's Planck satellite has produced, for the first time, a full-sky map of the SZ effect. Statistics of this map, such as one-point PDF and the power spectrum, provides a powerful test of our theory for structure formation in the Universe. Unlike gravitational lensing of the CMB, which probes structure formation of the total matter, the statistics of the SZ effect tests our understanding of baryonic structure formation on large scales. We present state-of-the-art simulation of the SZ effect, and discuss what we learned from comparing the simulation with the Planck data. In the last part of the talk, we present a new analytical model for non-thermal gas pressure on galaxy clusters, which plays a crucial role in physical understanding of what we see in simulations and observations of the SZ effect.

The barred inner region of the Milky Way

Main Colloquium
Prof. Ortwin Gerhard
ORATED
Max-Planck-Institut für extraterrestrische Physik

The central few kpc of our Galaxy, the Milky Way, are dominated by the gravitational field of the Galactic bar. This talk describes dynamical models of the bar and box/peanut bulge, and what we have learnt from them about the dynamical structure, the distribution of stellar and dark matter mass, and the spatial and orbital distributions of the Galactic stellar populations. Much of the Galactic bulge must have formed from the disk at early times, constraining possible scenarios for Milky Way assembly.

Optical polarisation monitoring of Narrow Line Seyfert 1 galaxies. The search for long rotations of the polarisation plane.

Lunch Colloquium
Dr. Emmanouil Angelakis
ORATED
MPIfR

The Narrow Line subset of Seyfert 1 galaxies are associated with nuclear black hole masses systematically smaller than those associated with large ellipticals that preferentially host very energetic jets. In 2009 and on the discovery of GeV emission from a handful of such sources introduced them as yet another class of gamma-ray bright AGNs while giving evidences for the presence of a blazer-like jet. On the basis the most systematic, multi-frequency radio monitoring we showed that gamma-ray emitting NLSy1s possess mildly relativistic jet that show all typical characteristics of blazer jets. This aligned scenario was later confirmed also by careful VLBA studies of the only suitable member of the class. With the current study we undertook the task to quantify and understand the dynamics of the optical polarisation from 10 radio loud Narrow Line Seyfert 1 galaxies. We concentrate on the fractional polarisation and the polarisation angle. We especially look for long (beyond 90 degrees) rotations of the polarisation plane that are seen in blazer jets. Along with presentation of our current findings I will also discuss our approach for assessing the probability that the observed events are the mere result of noise. We show that although nice can indeed induce such events it is much more likely that intrinsic rotations are indeed occurring. This is the first time that such a phenomenon has been observed in this class of sources.

Large-scale clustering in a nutshell: from the CMB to the Cosmic Web

Main Colloquium
Dr. Cora Uhlemann
ORATED
DAMTP, University of Cambridge, UK

Cosmic structure formation describes how the initially almost uniform matter distribution observed in the CMB gave rise to the late-time cosmic web – an intricate pattern of galaxies on the sky. To connect the almost perfectly Gaussian statistics of the CMB to the highly non-Gaussian statistics of the cosmic web, we need to understand the gravitational clustering of matter. I will explain how spherical collapse, a nonlinear solution of gravitational collapse in spherical symmetry, can be used to accurately predict the statistics of densities in spheres. I will show that those counts-in-cells statistics capture essential non-Gaussian properties of the cosmic web, including peculiar regions of very high and low density. Finally, I will give an outlook how this can be applied to galaxy surveys to probe key properties of our Universe, from the origin of structure to the late-time expansion.

New clues on the origin of nitrogen in the solar system

Main Colloquium
Dr. Pierre Hily-Blant
ORATED
UGA/IUF/IPAG, Grenoble

To which extent did the primitive solar system keep memory of its interstellar past is a key question from planetary science and astrophysical perspectives. More generally, what is the interstellar heritage of planetary systems ? Most of our knowledge about the earliest stages of the solar system comes from isotopic ratios, because they trace the history of volatile elements. Another such tracer is the ortho-to-para ratio of relevant species such as water. In this talk, I will focus on one element namely, nitrogen. Our starting point for the history of nitrogen in the solar system will be comets for which all observations converge towards a single value of the 14N/15N isotopic ratio of ~140. This threefold 15N-enrichment with respect to the elemental 14N/15N ratio of 441 in the PSN may have several origins: 1/ cometary carriers of the primary reservoir of nitrogen have not been observed so far, 2/ fractionation in cometary nuclei over the last 4.6 Gyr, 3/ fractionation in the protosolar nebula by e.g. selective photodissociation of N2, or 4/ fractionation in the interstellar cloud where the Sun formed. We will discuss these possibilities in the light of measurements of the nitrogen isotopic ratios performed recently in prestellar cores, protostars, disks, and comets. In particular, the direct measurement of the 14N/15N ratio in the disk orbiting TW Hya performed with ALMA rules out fractionation in cometar nuclei as an important process. The measured ratio of 323+/-30 in TW Hya is interpreted as the elemental isotopic ratio of nitrogen in the present-day solar neighbourhood, in excellent agreement with galactic chemical evolution models. I will also present the recent direct determination of the HCN/HC15N in the L1498 prestellar core, suggesting that nitrogen fractionation is not efficient in such a cold environement, although source-to-source variations cannot be excluded. I will also present recent models of the ortho:para chemistry in collapsing prestellar cores. Finally, I will conclude with current challenges from observational, theoretical, and modeling perspectives.

The Large Millimeter Telescope - early science and future opportunities

Special Colloquium
Dr. David H. Hughes
ORATED
LMT/INAOE, Mexico

The Large Millimeter Telescope (LMT) Alfonso Serrano is a 50-m diameter single-dish millimeter-wavelength telescope, optimized to conduct scientific observations at frequencies between ~70 and 280 GHz. The LMT is constructed on the summit of Sierra Negra at an altitude of 4600m in the Mexican state of Puebla. The LMT began shared risk early-science operations in 2014, including VLBI at 3mm and 1.3mm, using the inner 32-m diameter of the primary reflector with an active surface control system. Since early 2018 the LMT has begun scientific operations as a 50-m diameter telescope. I will describe the current status of the telescope project, the early scientific results, as well as the plan to improve the overall performance of the telescope and the development of the instrumentation program.

Let us discover the third family of compact stars!

Main Colloquium
Prof. David Blaschke
ORATED
University of Wroclaw, Poland

Sequences of stable solutions in the mass-radius diagram for compact stars are generally divided into two families: white dwarfs and neutron stars, separated by about three orders of magnitude in their radii due to their very different composition and the corresponding equation of state (EoS). When neutron star matter undergoes a phase transition due to, e.g., quark deconfinement and/or chiral symmetry restoration, at densities attainable in the neutron star interior then under certain conditions a third family of compact stars can occur and be populated. I discuss a few examples for the EoS of such hybrid star matter that would give rise to a third family of compact stars and fulfil all known constraints, in particular for the maximum mass from PSR J0438+432 and tidal deformability from GW170817. I argue that the measurement of a sufficiently large radius for the nearest millisecond pulsar J0437-4715 by NICER could rule out the scenario of a soft purely nuclear EoS (like SLy4 or APR) and provide evidence for the scenario of a third family of compact stars and thus for a strong phase transition in the EoS of cold dense matter in the interior of neutron stars with masses of about 1.4 Msun. The existence of a third family of compact stars would imply that a critical point in the QCD phase diagram must exist.

Light and shadow in the Galactic Center

Main Colloquium
Prof. Andreas Eckart
ORATED
Universität zu Köln

The luminous S-star cluster in the Galactic Center allows us to study the physics close to a super-massive black hole including distinctive dynamical tests of general relativity (Parsa, Eckart, Shahzamanian et al. 2017). Our best estimates for the mass of and the distance to Sgr A* are currently obtained using the three shortest period stars (S2, S38, and S55/S0-102). Additionally, we aimed at a new and practical method to investigate the relativistic orbits of stars in the gravitational field near Sgr A*. From VLT single dish adaptive optics data we derive estimates of the orbital deformation due to relativistic effects. Accepting this result, S2 is the first star on a spatially resolved orbit around a super-massive black hole for which a post-Newtonian effect has been measured. In addition we studied the central regions of the Galactic Center to determine if the Circum-Nuclear Disk (CND) acts as an absorber or a barrier for the central X-rays diffuse emission surrounding the super massive black hole (Mossoux & Eckart 2017). 4.6 Ms of Chandra observations allow us to detect, for the first time, a shadow against the diffuse X-ray emission whose extent and location correspond to those of the CND. This information is used to derive characteristic properties of the X-ray emitting medium in the central few parsecs. We deduced that the CND rather acts as a barrier for the Galactic Center plasma and that the plasma located outside the CND may correspond to the collimated outflow possibly created by Sgr A* or the interaction between the wind of massive stars and the mini-spiral material.

Type I shell galaxies as a test of gravity

Special Colloquium
Dr. Hajar Vakili
ORATED
Department of Physics, Sharif University of Technology, Tehran, Iran

Shell galaxies are understood to form through the collision of a dwarf galaxy with an elliptical galaxy. Shell structures and kinematics have been noted to be independent tools to measure the gravitational potential of the shell galaxies. We compare theoretically the formation of shells in Type I shell galaxies in different gravity theories in this work because this is so far missing in the literature. We include Newtonian plus dark halo gravity, and two non-Newtonian gravity models, MOG and MOND, in identical initial systems. We investigate the effect of dynamical friction, which by slowing down the dwarf galaxy in the dark halo models limits the range of shell radii to low values. Under the same initial conditions, shells appear on a shorter timescale and over a smaller range of distances in the presence of dark matter than in the corresponding non-Newtonian gravity models. If galaxies are embedded in a dark matter halo, then the merging time may be too rapid to allow multi-generation shell formation as required by observed systems because of the large dynamical friction effect. Starting from the same initial state, in the dark halo model the observation of small bright shells should be accompanied by large faint ones, while for the case of MOG, the next shell generation patterns iterate with a specific time delay. The first shell generation pattern shows a degeneracy with the age of the shells and in different theories, but the relative distance of the shells and the shell expansion velocity can break this degeneracy.

Searching for Pulsars in Unassociated Fermi-LAT Sources

Promotionskolloquium
Jason Wu
ORATED
MPIfR

In the past 10 years, the number of Gamma-ray pulsar has increased dramatically from 7 to 211 thanks to the superb performance of the Fermi Large Area Telescope (LAT). These observations have demonstrated that pulsars are by far the largest source class in the Galactic plane at GeV energies. In this talk I will describe the method I have used to select pulsar candidates from the third Fermi Large Area Telescope source catalog (3FGL). I will present the details of the radio pulsar survey using the Ultra Broad Band receiver at Effelsberg and the Gamma-ray pulsar blind search using the volunteer computing project Einstein@Home. I will present the 17 new pulsars found in our Gamma-ray blind search survey and discuss some of the implications of these results in terms of population statistics and pulsar emission properties. [Referees: Prof. Dr. Michael Kramer (Max-Planck-Institut für Radioastronomie), Prof. Dr. Norbert Langer (Argelander-Institut für Astronomie, Universität Bonn), Prof. Dr. Klaus Desch (Physikalisches Institut, University of Bonn) and Prof. Dr. Barbara Kirchner (Mulliken Center for Theoretical Chemistry, Institut für Physikalische und Theoretische Chemie, Universität Bonn)]

The Gaia mission: Objectives, status and early results

Main Colloquium
Dr. François Mignard
ORATED
Observatoire de la Côte d'Azur and CNRS

On the 14th September 2016 the European Space Agency and the European consortium DPAC have jointly released the first results of Gaia, precisely 1000 days after the launch. With one billions stars catalogued with accurate positions, the Gaia scientists have produced the best ever map of the sky. In addition a smaller astrometric catalogue with 2 million stars includes also their distances and annual motion on the plane of the sky. A small set of variable stars with light-curves and a reference system based on the extragalactic sources of the ICRF positioned for the first time in the visible are parts of this release. A second release is scheduled on April 25, 2018 with a larger catalogue and more than 1.2 billion parallaxes and proper motions, a kinematically non-rotating frame built on 550,000 quasars and several millions radial velocities. During the seminar I will summarise the main scientific objectives of the mission and the technical means implemented to achieve the goals and get at the mission completion positions, distances and proper motions of more than one billion sources. The main results of the Gaia DR1 will be outlined and I will describe in more detail the current status of the program and the content of the second release scheduled late April 2018.

Deciphering Quantum Information from Classical Black Holes

Main Colloquium
Prof. Jonas R. Mureika
ORATED
Department of Physics, Loyola Marymount University

Of all the predictions stemming from General Relativity, black holes are perhaps the most compelling and ubiquitous. These objects play a central role not only in astrophysics, but in fundamental physics as well. They are one of the few physical arenas wherein both quantum mechanics and gravitational effects are simultaneously present in the form of thermodynamics and information theory. Microscopic black holes have generally been expected to reveal the thermodynamic nature of gravity, but there is a growing conviction that larger black holes, including supermassive ones, may also reveal such effects. This talk will discuss this growing trend in black hole physics, as well as prospects for observing such quantum effects at the macroscopic scale in future experiments.

Hidden outflows and extremely obscured nuclei - starbursts or AGNs?

Main Colloquium
Prof. Susanne Aalto
ORATED
Onsala Observatory, Chalmers University of Technology, Sweden

Cold gas plays a central role in feeding and regulating star formation and growth of supermassive black holes (SMBH) in galaxy nuclei. Particularly powerful activity occurs when interactions of gas-rich galaxies funnel large amounts of gas and dust into nuclei of luminous and ultra luminous infrared galaxies (LIRGs/ULIRGs). These dusty objects are of key importance to galaxy mass assembly over cosmic time. It is also increasingly clear that feedback from star formation and AGNs is fundamental to regulating the evolution of galaxies in the nearby Universe as well as at earlier epochs. Mechanical feedback occurs in the form of winds (stellar, AGN, galactic), turbulence, supernova bubbles and superbubbles, AGN jets and backflows. With the advent of ALMA and the NOEMA telescopes we can now study the extent, morphology, velocity structure, physical conditions and even chemistry of these cold flows at unprecedented sensitivity and resolution. I will focus on recent ALMA and NOEMA studies of AGN and starburst outflows from dusty galaxies. In particular I will, for example, present recent ALMA studies with resolutions of 20-30 milli arcseconds (2 – 7 pc) of the launch regions of molecular outflows and jets in the nearby LIRGs NGC137,7 IC860 and Zw049. I will also show that one can use the JVLA telescope for high-resolution molecular observations of nuclear outflows. Finally, I will give the ALMA view of a double-outflow from the starburst galaxy NGC3256.

Energy equipartition between cosmic rays and magnetic fields

Special Colloquium
Amit Seta
ORATED
Newcastle University, UK

Interpretation of synchrotron intensity data requires knowledge of the cosmic ray number density, which is often assumed to be in energy equipartition (or otherwise tightly correlated) with the magnetic field energy density. We examine the energy equipartition assumption between cosmic rays and magnetic fields using both: test- particle simulations (important to capture the effect of magnetic field structure) and MHD simulations by considering cosmic rays as an additional diffusive fluid (important to consider the effects of gas pressure). We find no spatial correlation between the cosmic rays and magnetic field energy densities at turbulent scales. Moreover, the cosmic ray number density and magnetic field strength are statistically independent. Nevertheless, small-scale cosmic ray structures are abundant at low energies. These are particles trapped in random magnetic bottles. These conclusions can significantly change the interpretation of synchrotron observations and thus our understanding of strength and structure of magnetic fields in the Milky Way and nearby spiral galaxies.

The redshift distribution and dust properties of dusty star-forming galaxies at high redshift

Promotionskolloquium
Maria Louise Strandet Jensen
ORATED
MPIfR

In the colloquium I will present my thesis work on the Dusty Star-Forming Galaxies (DSFGs) from the South Pole Telescope (SPT) survey which are mostly gravitationally lensed galaxies at high redshift. We explore the high redshift nature of the SPT-DSFGs through ALMA redshift scans of 42 sources. We combine these observations with previously published and new mm/submm line and photometric data of the SPT-DSFGs to study their spectroscopic redshift distribution. This yields a sample of 62 sources with a median redshift of z = 4.1+/-0.2. To complete the redshift distribution for the full sample of 91 SPT-DSFGs we take advantage of the well sampled photometry of the sample. We determine redshifts by fitting Spectral Energy Distributions finding a median redshift of z = 3.7+/.0.1 for the full sample. For the sources with spectroscopic redshifts we determine dust temperatures and find a trend that dust temperatures are increasing with redshift. Among the SPT-DSFGs we found SPT0311-58 at z = 6.9, which is the highest-redshift millimeter-selected DSFG discovered to date. It has a large mass and is intensely star forming, which is very rare for a source well into the Epoch of Reionization. Examination committee: Prof. Dr. Karl M. Menten, Prof. Dr. Cristiano Porciani, Prof. Dr. Ian Brock, Prof. Dr. Christiane Dahl

Localizing a Fast Radio Burst and unveiling its extreme environment

Main Colloquium
Dr. Benito Marcote
ORATED
JIVE, Dwingeloo, The Netherlands

Fast Radio Bursts (FRBs) are radio transient sources that emit a single pulse with a duration of only a few milliseconds. They were firstly discovered in 2007, and nowadays we have detected tens of these events using single-dish radio observatories. Only one FRB has been precisely localized, FRB 121102, the only one known to repeats. In this talk I will focus on the results obtained from the localization of FRB 121102 performed in early 2017 and new observations conducted during the last year. We show that the bursts are coincident with a persistent and compact (<0.7 pc) radio source within a projected separation of less than 40 pc. These results, together with the recent detection of a surprisingly high rotation measure of the burst emission, only seen in the vicinity of Sagittarius A*, point to an extreme environment for FRB 121102.

Radio properties of SDSS-FIRST sources across optical diagnostic diagrams

Lunch Colloquium
Dr. Michal Zajacek
ORATED
MPIfR

The empirical relations between supermassive black holes and their host spheroids point towards a crucial role of galactic nuclei in the galaxy evolution. A detailed understanding of how the activity of a galactic nucleus regulates the growth of its host is still missing. To understand the role of an active galactic nucleus in the galaxy evolution, it is essential to study radio-optical properties of a large sample of extragalactic sources. In particular, we studied the radio spectral index distribution across the optical emission-line diagnostic diagrams. Using the SDSS, FIRST surveys and the Effelsberg measurements, we inferred the three-point radio spectral-index distribution for star-forming, composite, AGN Seyfert, LINER galaxies. Taking into account the previous analysis for larger radio flux densities at 20 cm (Vitale et al. 2015), we can confirm the trend of the radio spectral index flattening from composites, through AGN Seyferts, to LINERs. We will discuss the implications of this trend for the galaxy evolution across the optical diagnostic diagrams.

The Sardinia Radio Telescope

Special Colloquium
Dr. Valentina Vacca
ORATED
INAF, Osservatorio Astronomico di Cagliari, Italy

The Sardinia Radio Telescope is the new single dish facility operated by the Italian National Institute for Astrophysics (INAF). During this talk, I will summarize the available receivers and backends, report about the scientific results from its opening ceremony to date and give an overview of the present status.

SDSS V: Pioneering Panoptic Spectroscopy

Main Colloquium
Prof. Hans-Walter Rix
ORATED
MPIA, Heidelberg

SDSS V will be an unprecedented all-sky, multi-epoch spectroscopic survey of over six million objects. It is designed to decode the history of the Milky Way galaxy, trace the emergence of the chemical elements, reveal the inner workings of stars, provide a better census of stellar mass black holes in the Galaxy, investigate the origin of planets, and understand the growth mechanisms of supermassive black holes. It will also create a contiguous spectroscopic map of the interstellar gas in the Milky Way and nearby galaxies that is 1,000 times larger than the state of the art in the optical; this can uncover the self-regulation mechanisms of our Galactic ecosystem. It will pioneer systematic, spectroscopic monitoring across the whole sky, revealing spectral changes on timescales from 20 minutes to 20 years. SDSS V will accomplish its high survey speed, covering the entire sky repeatedly, by a combination of dual-hemispheres wide-field telescopes and a focus on bright objects, matched to Gaia, Kepler, TESS and also eROSITA. I will talk about the status, the scientific potential and the practical challenges of this recently initiated project, which is planned to start surveying in 2020, and is still building its consortium of partner institutions...

The physics and chemistry of oxygen-rich circumstellar envelopes as traced by simple molecules

Promotionskolloquium
Ka Tat Wong
ORATED
MPIfR

Different physical and chemical processes in the circumstellar envelopes (CSEs) of evolved stars, such as stellar pulsations, mass loss, shocks, and dust formation, can be studied by observing the molecular line emission and absorption in these environments. Recent advances in instrumentation for (sub)millimetre and far-infrared observations, such as the Herschel Space Observatory and the Atacama Large Millimeter/submillimeter Array (ALMA), allow us to probe the inner parts of the CSEs in great detail. In this colloquium, I will present two studies of the CSEs of oxygen-rich evolved stars. The first study focuses on the long-standing puzzle of ammonia (NH3) abundance. The observationally derived NH3 abundance is several orders of magnitude higher than that predicted by chemical models. In order to better characterise the distribution and excitation of NH3 in CSEs, multi-wavelength observations have been carried out towards four oxygen-rich stars with telescopes including the Karl G. Jansky Very Large Array (VLA), Herschel Space Observatory, and the NASA Infrared Telescope Facility (IRTF). In the second study, omi Cet (Mira) was observed with the longest baselines of ALMA. The stellar radio photosphere and molecular transitions of the surrounding gas were imaged at an unprecedented angular resolution of about 30 milli-arcsecond near 220 GHz (1.3 mm). For the first time, molecular line absorption against the stellar background has been clearly imaged at these wavelengths. Radiative transfer modelling of SiO and H2O lines and the comparisons with the predictions from hydrodynamical models will be presented. [Referees: Prof. Dr. Karl M. Menten (Max-Planck-Institut für Radioastronomie), Prof. Dr. Norbert Langer (Argelander-Institut für Astronomie, Universität Bonn), Prof. Dr. Stephan Schlemmer (I. Physikalisches Institut, Universität zu Köln), and Prof. Dr. Diana Imhof (Pharmazeutisches Institut, Universität Bonn)]

Continuous Gravitational Waves from Neutron Stars: Close to Detection or an Impossible Dream?

Main Colloquium
Dr. Alessandro Patruno
ORATED
Leiden University and ASTRON

A long standing question still open to debate is whether neutron stars are efficient emitters of continuous gravitational waves. The detection of such signals could open a new way to explore the structure of the neutron star interior, which hides many important answers about the working of nuclear forces and strong gravity. In this talk I review what is known about the neutron star structure and what is the evidence in favor and against the existence of such signals. I will discuss the spin distribution of neutron stars, the role of the magnetic field and some possible observational tests that could be performed in the future to try to settle the debate.

Uncovering the Protostars in Serpens South with ALMA: Continuum Sources and Their Outflow Activity

Special Colloquium
Dr. Adele Plunkett
ORATED
European Southern Observatory, Chile

The formation and evolution of protostars and their cluster environment are topics whose study utilizes the sensitivity, angular and spectral resolution, and mapping capabilities recently provided with ALMA. Serpens South is a young protostellar cluster that caught attention upon its discovery in Spitzer IRAC observations for the following reasons: (1) a high protostar fraction that indicates very recent and ongoing star formation; (2) iconic clustered star formation along a filamentary structure; (3) its relative proximity within a few hundred parsecs. In this talk I will present a multi-faceted ALMA data set, including maps of millimeter-wave continuum sources and molecular outflows throughout the region, as well as a more focused kinematical study of the protostar that is the strongest continuum source at the cluster center. Currently, we focus on the 52 protostar candidates detected near the cluster center, many of which are deeply embedded sources that could not be detected with Spitzer IRAC, and/or low-flux (low-mass) sources never before detected in mm-wavelengths. We find evidence of mass segregation and clustering according to the Minimum Spanning Tree method, distribution of projected separations between unique sources, and concentration of higher-mass sources near to the dense gas at the cluster center. Given the young age of this cluster, the mass segregation is likely primordial.

Growing black holes: from the first seeds to active galactic nuclei

Main Colloquium
Dr. Mar Mezcua
ORATED
Institut of Space Sciences (IEEC-CSIC), Barcelona

How supermassive black holes form and grow is still one of the long-standing questions in astronomy. Supermassive black holes of up to 10^10 solar masses already existed when the Universe was less than ~1 Gyr old. To reach this mass in such a short time, they should have started as seed intermediate-mass black holes (IMBHs) of 100-10^6 solar masses and grow very fast via accretion and mergers. Such IMBHs are the missing link between stellar and supermassive black holes and they should be present in the nucleus of low-mass galaxies and in the halos of large galaxies, e.g. in the form of ultraluminous X-ray sources (ULXs). In this talk I will present observational evidence that a population of IMBHs in dwarf galaxies similar to those seed black holes populating the early Universe exists. With the use of large, deep, multiwavelength surveys like COSMOS, these sources are detected up to z~2. I will also show that, in the local Universe, IMBHs can be additionally detected as extreme ULXs with powerful radio emission in galaxies having undergone a minor merger event. The later supermassive black hole growth can be explained by the accretion of gas coming from galactic scales. At kpc scales, this gas can be transported to the nuclear regions through galaxy mergers, which can trigger active galactic nuclei (AGN) activity and can be detected in the form of binary AGN. At scales of a few 100 pc, dust lanes can be the channels of inflow of material from the outer parts of the galaxy to the nuclear region, as evidenced by the finding that the spiral structure of the nuclear cold molecular gas traced by ALMA observations correlates with that of the dust. The nuclear dust lanes are in addition able to obscure the nucleus of low-luminosity AGN and to explain the collimation of the ionised gas, which questions the role of the dusty torus proposed by the Unified Model of AGN. 

Hydrodynamic simulations of the formation of galaxies

Special Colloquium
Dr. Pierluigi Monaco
ORATED
Dipartimento di Fisica, Sezione di Astronomia, Università di Trieste, Italy

Great progress has recently been achieved in simulating the formation and evolution of galaxies. In this case initial conditions, consisting in a scalar field of density perturbations, are set by the standard cosmological model, but the processes that shape the formation of galaxies as we know them take place on such a wide range of scales that a large number of these processes must be treated with sub-resolution techniques. I will review recent attempts to model the formation of galaxies, with emphasis on feedback processes from young and dying stars and from accreting supermassive black holes, that are most relevant for reproducing plausible galaxies, and will show recent progress on the panchromatic modelling of their spectral energy distributions.

Relativistic jets from black holes and neutron stars

Main Colloquium
Prof. Rob Fender
ORATED
Oxford Astrophysics

Relativistic jets are established to be a key feedback channel during specific configurations (rate, geometry, optical depth) of the accretion flow around all relativistic objects. I will summarise the current state of the art in our understanding of how the mode and power of such jets connects to the properties of the accretion flow around stellar-mass black holes, and discuss similarities and differences with such flows around neutron stars. I will highlight the pathological case of the nearby black hole V404 Cyg which underwent a bright and highly unusual outburst in June 2015, and discuss the future prospects for radio observations of such systems with new facilities such as MeerKAT and the SKA.

Unraveling interstellar chemistry with broadband rotational spectroscopy: PAHs and molecules in vibrationally excited states

SFB Colloquium
Prof. Melanie Schnell
ORATED
Deutsches Elektronen-Synchrotron (DESY), Hamburg

In the interstellar medium (ISM), chemical reactions are taking place in both the gas phase and on grain surfaces, which build up the complexity of organic molecules. We provide high-resolution laboratory data, obtained with broadband chirped-pulse rotational spectroscopy and various advanced light sources, such as Free-Electron Lasers (FELs) and synchrotrons, to improve the knowledge of the chemical inventory of the ISM and potential chemical mechanisms. We are particularly interested in polycyclic aromatic hydrocarbons (PAHs) and molecules in vibrationally excited states. While it is postulated that PAHs are at the basis of a rich chemistry, there has been no direct detection of individual types of PAHs in astronomical environments. We use a multi-spectroscopic approach to investigate PAHs and their chemistry. We employ broadband rotational spectroscopy to determine their structures and to investigate the hydration of PAHs to set a foundation for the future exploration of potential ice formation pathways. Far-IR spectroscopy allows us to study the global vibrations at low energies and the effect of anharmonicity. X-ray spectroscopy and VUV-UV and VUV-IR pump-probe spectroscopy provides insight into potential mechanisms for the interplay between ionization and fragmentation when interacting with harsh radiation. Molecules in vibrationally excited states are interesting from a spectroscopic point of view and can provide information about the physical conditions of their environment. For this, we use a segmented W-band spectrometer (75–110 GHz), which provides direct overlap with ALMA band 3, and perform the experiments under room-temperature conditions. This approach thus provides access to high-resolution, pure rotational data of vibrational modes that occur in the far-infrared fingerprint region and that can be difficult to access with other techniques.