Promotionskolloquium
Georgios F. Paraschos	ORATED

Max-Planck-Institut für Radioastronomie, Bonn, Germany

In this presentation, I will discuss our results from studying the radio source 3C 84 associated with the active galactic nucleus of the galaxy NGC 1275. The focus is put on high-frequency very-long-baseline interferometry studies, which provide the resolution to explore the innermost regions of the observed core-jet morphology. Data observed at three wavelengths (20, 7, and 3.5 mm) have been combined to probe the emission and absorption of the synchrotron radiation and the magnetic field configuration: the spectral index of the central region reveals a gradient (values range between +2 and -1.5 between 7 and 3.5mm), the jet apex is about 400-1500 Schwarzschild radii upstream of the 3.5-mm core, and the magnetic field appears to be a combination between poloidal and toroidal, with a strength of 2–4 Gauss. Imaging results of the central region at 3.5-mm are also presented, further constraining the position of the jet apex. The analysis reveal a possible change of the viewing angle of the relativistic flow, with an upper limit of 35 degrees. Images of the source over 20 years reveal the kinematics of the plasma regions, as well as the jet shape: the latter appears to be frequency dependent, caused by a spine-sheath jet stratification scenario. The spectral index between 7 and 3.5 mm shows a gradient, suggesting the black hole to be off-centered from the total intensity radio maximum. Note: Talk presented at the Seminar Room 1 of the I. Physikalischen Institut of the Universität zu Köln

	Main Colloquium
Dr. Frank Schinzel	ORATED

NRAO, USA

Studying the dynamics inside complex supernova environments is challenging. Following a supernova explosion, a newly formed pulsar is embedded in the ambient medium. In rare cases, the pulsar can get a significant 'kick' from the initial explosion and may escape its surrounding supernova remnant to interact with the interstellar medium (ISM). This talk will discuss probably one of the best of such cases recently discovered. I will be illustrating the journey that led to the discovery of the pulsar wind nebula (PWN) related to the high 'kick' velocity PSR J0002+6216, followed by a discussion of our recent results from spatially resolved X-ray observations taken with the Chandra X-ray observatory and combined with multi-epoch multi-frequency radio observations with the Very Large Array. These observations are providing unique insights into the bow-shock properties of this PWN and the interaction of the cometary-like tail with the ISM surrounding the supernova remnant CTB 1. I will also include a brief summary of the challenging High Sensitivity Array (VLBA+VLA+Effelsberg) observations, concluded this July, to constrain the parallax distance to PSR J0002+6216. I will end with an outlook addressing a missing population of young gamma-ray pulsars in the Galactic plane, with the potential of finding more young pulsars with rare properties.

	Special Colloquium
Sergio Poppi	ORATED

INAF, Osservatorio Astronomico di Cagliari, Italy

The Sardinia Radio Telescope (SRT) is a 64-metre single dish radio telescope operating from 300 MHz to 26.5 GHz. In 2019 the Italian National Institute for Astrophysics (INAF) was awarded funds to extend the infrastructure to observe at high frequencies, up to 116 GHz, either in single-dish or VLBI mode. Thus, in this presentation it will be shown the upgrade of the SRT which includes state-of-the-art receivers, back-end, high-performance computing, a new metrology system and also, new instrumentation for laboratories.

	Main Colloquium
Dr. Thushara Pillai	ORATED

MIT Haystack Observatory, USA

Stars form during gravitational collapse in molecular clouds. This process governs how galaxies evolve over cosmic time by creating their stellar components. It also affects properties of the planets formed along with the young stars. Collapse in molecular clouds during star formation is controlled by self–gravity, random “turbulent” gas motions inside clouds, and interstellar magnetic fields. Past studies have revealed a detailed picture of the role of self–gravity and gas kinematics during star formation — but observational assessments of magnetic fields remain challenging. A coordinated and ambitious project is needed to systematically fill the gaps in our current understanding of magnetic fields in star formation. SIMPLIFI (“Study of Interstellar Magnetic Polarization: a Legacy Investigation of FIlaments”) is primarily a SOFIA legacy project designed to study a sample of molecular clouds at near (d < 500 pc) and intermediate (d <5 kpc) distances in polarized Far-IR light. Near-IR starlight polarization combined with Gaia data provide information on the connection of dense clouds to its diffuse natal environment. SIMPLIFI also uses molecular line emission to study the relative alignment of gas flows and magnetic fields and tests key theoretical predictions of MHD turbulence. I will present highlights from the pilot survey program that start to clarify the role of magnetic fields in a diverse sample of star-forming filaments, and provide a framework to simplify the diversity of filament properties.

	Special Colloquium
Ryan Keenan	ORATED

University of Arizona, Tucson, USA

The J=1-0 transition of the CO line has long been the canonical tracer of molecular gas. However, the improved sub/millimeter facilities, the push for higher resolution, and a growing interest in high redshifts all favor observations with the higher frequency CO(2-1) line. Recent studies have found evidence that CO(2-1)-CO(1-0) line ratios vary between galaxies of different types and across galactic environments, suggesting that care is needed when interpreting CO(2-1) as a tracer of bulk molecular gas. These results are complicated considerably by the difficulty of comparing millimeter data collected with different facilities. Calibration issues produce systematic uncertainties comparable to the dynamic range of trends found in recent studies and resolved measurements can produce contradictory results depending on the datasets used. I will present the Arizona Molecular ISM Survey with the SMT (AMISS), a multi-CO line survey of ~200 nearby galaxies designed to understand CO line ratios across a broad range of galaxy properties. AMISS uses data from a single telescope for each line, with careful attention to calibration, which allows us to overcome many of the challenges in measuring line ratios. The large size of our survey allows us to identify trends between galaxy properties and CO line ratios. In particular we find a correlation between CO(2-1)/CO(1-0) and galaxy-integrated star formation rate. This effect propagates to the slope of the Kennicutt-Schmidt relation, giving different slopes for measurements made with different lines. I will discuss how these results impact the interpretation of CO(2-1) studies at high and low redshifts, and motivate the need for resolved, multi-CO line surveys of larger samples of galaxies.

	Special Colloquium
Dr. Anaëlle Maury	ORATED

CEA-Saclay and Harvard-Smithsonian CfA

Wherever we have the means of observing them, magnetic fields are detected across the full spectrum of astrophysical environments, from our own Earth, to stars, and cosmological structures. Magnetic fields are also present at all scales and evolutionary stages of star-forming structures. They have long been suspected to play a key role in shaping the typical outcome of the star formation process, such as stellar mass, spin, and multiplicity, or even the fate of stars towards their ultimate stages. In this talk, I will provide a global outlook on the progresses made in the recent years to characterize the role of magnetic fields during the embedded phases of the star formation process. Thanks to the development of observational capabilities and the parallel progress in numerical models capturing most of the important physics at work during star formation, we have successfully confronted detailed predictions of magnetized models to observational properties of the youngest protostars. I will present the physical processes and observational methods allowing to trace the magnetic field topology and its intensity in embedded protostars, and review the main steps, success and limitations in comparing real observations to synthetic observations from the non-ideal MHD models. I will describe in more details the physical conditions required to ensure an efficient magnetic field coupling, and present our work characterizing the two main agents responsible for the coupling in star-forming cores: dust grains and ionized gas. Following this Ariane thread, I will argue our observational and theoretical findings support a novel scenario where the magnetic field and the evolution of dust grains around solar-type protostars are tightly linked. Putting them in the broader context of protoplanetary disk studies, I will show how these findings deeply modify our paradigm of planet formation, ultimately shedding light on the formation and properties of exoplanetary systems, a fascinating question which has been at the heart of our quest to define mankind and the conditions for life to develop in a broader context. I will conclude by describing promising avenues to further explore the properties of young stars and the planets forming around them, their magnetic fields and dust pristine properties, getting the best fruition from future developments of both observational and computational capabilities.

	Main Colloquium
Dr. Catherine Zucker	ORATED

Space Telescope Science Institute, Baltimore, Maryland, USA

Given its proximity, the solar neighborhood has long been considered a fundamental laboratory for understanding how stars form. However, until very recently, this understanding was largely based on static ''plane of the sky'' views, making it extraordinarily challenging to build a 3D physical picture of gas and young stars using 2D integrated quantities. In this talk, I will discuss how new 3D spatial and dynamical constraints from Gaia, in combination with new data science and visualization techniques, have transformed our understanding of star formation near the Sun. In particular, I will show how ''3D dust mapping'' has provided never-before-seen 3D spatial views of the interstellar medium: redefining the structure of the Local Arm of the Milky Way, giving rise to previously undiscovered superbubbles, and constraining the detailed morphologies of individual molecular clouds at 1 pc resolution. Combining 3D dust mapping with the 3D space motions of young stars, I will show how we can reconstruct the star formation history of the solar neighborhood over the past 20 Myr, and in doing so, explain the origin of all nearby star formation as being driven by the expansion of the Local Bubble. I will conclude by discussing new opportunities with Gaia DR3, as well as the implications of our results for the theory and simulation communities.

	Promotionskolloquium
Parichay Mazumdar	ORATED

MPIfR

Molecular Cloud (MC) surveys play a crucial role in helping us understand their structure and composition. In addition, they are also essential in understanding the theory of star formation and testing various models of the Milky Way. During this thesis defense, I will present the work done on starting a new large-scale high-resolution survey (LAsMAGal) of giant molecular clouds (GMCs) in the Milky Way. The proposed survey is a first of its kind which simultaneously covers both 12CO and 13CO (3-2) lines. It also has a higher angular resolution and sensitivity than previous surveys of the southern Milky Way. I will first motivate the need for a new survey and present the results of the pathfinder study conducted to kick start the survey and test the feasibility of various observing strategies. Following this, I will demonstrate the capabilities of the new survey by presenting the observations taken towards the G305 star-forming GMC to study the effects of stellar feedback on the GMC. LAsMAGal data in combination with other ancillary survey data were used to investigate how the feedback from the central cluster of OB stars in G305 impact three separate aspects of the GMC, namely gas excitation, dynamics, and star-forming ability. I will conclude by briefly stating the current status of the survey and other science being carried out using LAsMAGal data. [Referees: Prof. Dr. Karl M. Menten , Prof. Dr. Pavel Kroupa, Prof. Dr. Klaus Desch, Prof. Dr. Matthias B. Hullin]

	Special Colloquium
Prof. Amélie Saintonge	ORATED

University College London, UK

Galaxy evolution is regulated by gas accretion from the intergalactic medium, the cooling and processing of this material into stars in the interstellar medium, and the return of some of the gas and metals to the circumgalactic environment via feedback processes. This framework is built upon an extensive network of observed scaling relations between galaxy physical properties, many of which are crucially measured through large dedicated surveys at submm/mm wavelengths with facilities such as IRAM, JCMT, APEX and ALMA. In this talk, I will review key results from such studies of the cold ISM of nearby galaxies, with a particular emphasis on the systematic variations in star formation efficiency and ISM physical properties, and the lessons they teach us about galactic-scale processes such as star formation, dust production/destruction, mixing and gas transport. I will also argue that much needed breakthroughs in our understanding of star formation and galaxy evolution will come from the next generation of (sub)mm facilities, which will allow us to connect the cold ISM of large samples of galaxies with the environment that feeds them (the circumgalactic medium, in particular), and to quantify the impact of the galactic environment on the star-formation process on molecular cloud scales, both at low and high redshifts, as a stepping stone towards a universal theory of star formation.

	Main Colloquium
Prof. Robin Garrod	ORATED

University of Virginia

Reactions on dust-grain surfaces are responsible for the production of many important interstellar molecules, including gas-phase H2, grain-surface ice species such as water, ammonia and methanol, and arguably some of the most complex molecules detected in star-forming regions. However, our view of the temperature dependence of this chemistry has recently been changing. A major driver in this shift is the gas-phase detection of complex organic molecules (COMs) such as methyl formate in cold pre-stellar cores. These detections have pushed back the astronomical clock on COM production, to a time much earlier than the warm proto-stellar stage in which they are usually detected (albeit in much greater abundance). Experimental evidence also suggests that COMs may be formed on very cold surfaces (~10 K), through mechanisms that do not require thermal diffusion of the reactants. Past models that rely solely on diffusive reaction mechanisms now appear inadequate. I will discuss new modeling treatments that adopt a more comprehensive framework for grain-surface and ice-mantle chemistry, allowing reactants to meet in a variety of ways that do not rely solely on diffusion. This allows COMs to form as the ice mantles grow, while processing of the ices by external and cosmic-ray-induced UV fields can also lead to COM production. The period when the water-dominated ices desorb from the grains also allows trapped radicals to meet and react on the warm ice surfaces, prior to desorption. Gas-phase chemistry can further enhance COM production in some cases. In combination, these processes allow COMs to form over a range of temperatures, through a variety of mechanisms. I will discuss the implications of this new picture of COM chemistry on the origins and abundances of both familiar and more unusual COMs in star-forming regions.

	Special Colloquium
Prof. Jeroen Stil	ORATED

University of Calgary, Canada

The HI/OH/Recombination line (THOR) survey includes the first broad-band (1 - 2 GHz) spectro-polarimetric continuum survey of the inner Milky Way. This allows polarimetry and measurements of Faraday rotation for Galactic and extragalactic sources over a large section of the first Galactic quadrant. After a brief introduction of THOR, I will introduce how broad-band polarimetry enhances Faraday rotation as a probe of Galactic magnetism, illustrated by three results from the THOR polarization survey. First, I will present a new view of Faraday rotation associated with the Milky Way's large-scale magnetic field in the first quadrant. Second, THOR's broad-band polarimetry of supernova remnants reveals their internal Faraday rotation. The third example addresses magnetic field structure on sub-parsec scales by differential Faraday rotation across extragalactic sources behind the Milky Way. These examples serve to show the rich data that modern spectro-polarimetric surveys like THOR have to offer.

	Main Colloquium
Dr. Tyrone Woods	ORATED

NRC Herzberg Astronomy and Astrophysics Research Centre, Victoria, Canada

The discovery of billion-solar-mass quasars at redshift ~ 7 challenges our understanding of the early Universe — how did such massive objects form in the first billion years, and what can this tell us about their environments at Cosmic Dawn? Observations and theory increasingly favour a "heavy seed" or "direct collapse" scenario, in which the rapid accretion possible in some primordial halos leads to the formation of uniquely supermassive stars, which collapse to form the initial seeds of supermassive black holes. In this talk, I'll present systematic, self-consistent simulations of the evolution of these objects under realistic formation conditions, and propose observational diagnostics to decisively test the origin of high-z quasars using next generation electromagnetic and gravitational wave observations. I'll also discuss the expected multiplicity of such supermassive stars and their subsequent interactions, as well as the unique observational signatures of primordial stellar populations which are intermediate in mass between supermassive objects and "typical" Pop III stars detectable by JWST and next generation observatories in the coming years.

	Special Colloquium
Dr. Riwaj Pokhrel	ORATED

Department of Physics and Astronomy, University of Toledo, USA

One of the well-established empirical results in astronomy is the Kennicutt–Schmidt relation between the surface density of interstellar gas and the rate at which the gas forms stars. A tight correlation between these quantities has long been measured at galactic scales. However, until recently the correlations on molecular cloud scales are found to vary between individual clouds. Through the Spitzer Extended Solar Neighborhood Archive (SESNA) and a matching Herschel archival effort, we have compiled huge, uniform maps of the structure of young star distributions and molecular gas for twelve nearby (<1.5 kpc) molecular clouds. In this talk, I will present a comprehensive analysis of the relation between star formation rate density and mass surface density of molecular gas over a wide range of sampling scales based on SESNA and Herschel observations. The ``universal” star formation relations in the star-forming clouds in the solar neighborhood will be discussed. I will also provide a brief update on other recent progress on observed star formation relations and simulation efforts and challenges in trying to explain the observed star-gas correlations.

	Master Colloquium
Reem Aboelsoud	ORATED

Max-Planck-Institut für Radioastronomie

Studying the chemical composition of the molecular clouds in the central regions of galaxies helps us to infer the type of the nuclear activity. NGC5195, or M51b, is an iconic example of a nearby galaxy that had a recent interaction with its companion, M51, 50-500 Myr ago. In this thesis, we used NOEMA data to study the nucleus of NGC5195, its nuclear activity, and the effects of the interaction on its ISM. High resolution observations of CO(1-0), CN(1-0), HCN(1-0), HCO+(1-0) and HNC(1-0) towards the galaxy (2'' ~ 100 pc) were performed. Comparison between the spectra at the position of the nuclear source and the whole mapped area enabled us to investigate the nature of NGC5195 central activity. We conclude that an active AGN is likely not powering the galaxy. In addition to the moment maps of all lines, which show the intensity distribution, velocity fields and velocity dispersion, we also studied the intensity integrated ratio maps among CO/CN, HCN/CN, HCN/HCO+, CO/HCN, and HCN/HNC. The most interesting ratios were CO/HCN and CO/CN. Those two ratios show that M51b has two twin peaks in the East-West direction of the center. These peaks are oriented nearly perpendicular to the large scale bar and connected to a curved structure. The nucleus of M51b is surrounded by concentrations of dust, making a ring shape, and we found that the radius of the dusty ring is spatially coincident with the two molecular peaks found in our work. We have also studied how the source of the nuclear activity could affect the values of some molecular ratios. To make this comparison, we chose our galaxy observation, M51b, and 8 other galaxies, including starburst galaxies (M83, NGC 253 and M82), galaxies hosting AGNs (NGC 1068, NGC 7469 and M51), ULIRGs (Arp 220 and Mrk 231). What differentiates NGC5195, in comparison to the rest of the galaxies, is its post-starburst phase after its interaction with M51, which is characterised by a large amount of diffused gas, resulting in a high CO/HCN ratio. [Referees: Prof. Dr. Karl Menten, Prof. Dr. Frank Bigiel]

	Main Colloquium
Dr. Violette Impellizzeri	ORATED

Leiden Observatory, The Netherlands

Active galactic nuclei (AGN) play an important role in the shaping and evolution of galaxies. However, understanding their properties has been challenging due to the extraordinary sensitivity and resolutions required to study them. Such detailed observations are finally becoming accessible thanks to ALMA, VLTI and high sensitivity VLBI observations. In this talk, I will present results of the prototypical Seyfert 2 nucleus in NGC 1068. We have now obtained data with a factor 2 better resolution (1 pc-scale) with the most extended ALMA configurations, revealing clear indications of an outflow originating from the nucleus (consistent with the outflow observed in CO), and the presence of two nested, rotating disk components. The inner disk, inside 1.5 pc, has kinematics consistent with the edge-on, geometrically thin H2O water megamaser disk. The outer disk, which extends to 7 pc, is also geometrically thin but inclined. The outer disk counter-rotates relative to the inner, water megamaser disk. I will conclude with a picture in which the torus consists of two geometrically thin, counter-rotating disks, and the nuclear obscuration occurs in outflowing molecular clouds whose origin is likely a hydromagnetic wind driven off of the inner disk. I will also present new, sensitive VLBI observations of the water megamasers releasing for the first time the existence of linear substructures, or ''spokes,'' among the maser spots that suggest the influence of magnetic fields. The position-velocity diagram shows curvature consistent with elliptical orbits or spiral arm structure within the megamaser disk. We find that a warped-disk model fits the data well, and the de-projected model reveals candidate spiral arm structures. Finally, we were able to recover the 22 GHz continuum on short baselines. The resulting continuum image shows a distorted X-shaped morphology, which we can match with VLTI observations, changing our picture of the inner core dramatically. One arm of the X aligns with the m aser disk, suggesting that the continuum arises in an edge-on plasma disk. The other arm orients more nearly perpendicular to the maser disk, resembling sub-parsec lobes in an ionized outflow or jet.

	Informal Colloquium
Prof. Dr. Yoshiaki Hagiwara	ORATED

Toyo University, Japan, ASTRON/JIVE Visiting Scientist

*** Warning: room changed, now it is the library seminar room 2.05*** The most recent front-end developments for 4 x 20m radio telescopes of VLBI Exploration of Radio Astrometry (VERA) will be reported. We will show a brief overview of currently ongoing technical developments of a dual circular polarization receiving and ultra-wide band (16 Gbps) recording systems that have been installed to each of the 4 telescopes of VERA. With these developments for the wide band VLBI polarimetry, it is now possible to study magnetic field properties of radio jets in active galactic nuclei, masers in star-forming sites, and stellar envelopes in late-type stars at unprecedented sensitivity. The observing performance obtained from most recent performance test observations will be also presented.

	Special Colloquium
Dr. Víctor Patiño-Álvarez	ORATED

MPIfR-INAOE Partner Group Leader, Instituto Nacional de Astrofísica, Óptica y Electrónica, Puebla, Mexico

I will present some of the results obtained during the last three years by myself and the INAOE AGN Group, including the work of the Master and PhD students. Among the multiwavelength variability studies I will mention the results of different papers on the sources 3C 273, CTA 102, 3C 454.3, B2 1633+382, and PKS 1510-089. I will talk about the correlations obtained between the variability at pc-scales and the gamma-ray variability, for the sources 3C 279 and 3C 454.3; this with the objective of directly locating gamma-ray emission regions on the VLBA maps (and we succeeded). Lastly I will briefly talk about the Baldwin Effect, which is a relationship between spectral characteristics of AGN, that despite being studied for over four decades, there was no consensus on the driving mechanism of said relationship. However, we present observational evidence that probes that the Baldwin Effect is a direct and natural consequence of the relationship between the ionizing continuum and the emission line luminosities.

	Main Colloquium
Dr. Ian Heywood	ORATED

University of Oxford, UK

The South African MeerKAT telescope recently marked four years since inauguration, and three years of scientific observing in pursuit of its large survey programs and open time projects. I will present results from three imaging projects that I have been involved in, covering extragalactic deep fields from the MIGHTEE survey, a study of an unusual pulsar that was a joint venture between MeerTRAP and ThunderKAT, and an update on the observatory-led Galactic centre survey. I will discuss some of the data processing advances and challenges that have resulted from this work.

	Main Colloquium
Dr. Jumei Yao	ORATED

National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China

SNR shells have long been suspected as the culprits for dominating pulsar scattering. The interstellar scintillation observation of pulsars associated with SNRs provide us with great opportunity to find evidence for this and reveal the properties of the compact ionized structures. Using FAST, we did high sensitivity interstellar scintillation and polarization observations of PSR J0538+2817 and PSR J0659+1414. For PSR J0538+2817, we found that the shell of SNR S147 dominates its scattering and detected the first evidence for pulsar three-dimensional spin-velocity alignment. The scattering of PSR J0659+1414 is dominated by two different compact regions, the shell of the Monogem ring and the Local Bubble. And the polarization analysis shows that the spin and velocity vectors of PSR J0659+1414 are significantly misaligned.

	Master Colloquium
Shampa Bhusal	ORATED

Max-Planck-Institut für Radioastronomie

Globules, associated with H II regions, are one of the best laboratories to study the impact of stellar radiation and feedback from expanding H II regions on the surrounding medium. First detected by A. D. Thackeray (1950) in the southern H II region IC 2944, the so-called Thackeray’s globules are prime examples of such objects. In this thesis, I present APEX telescope observations of the largest globule in the complex, Thackeray 1, in low level rotational transition of CO and [CI], together with an unbiased spectral line survey in the 230 GHz atmospheric window. I have used this data to probe the physical and chemical conditions of the molecular gas and the photo dissociation regions (PDR) in Thackeray 1. The velocity resolved CO observations suggest that the largest globule is the overlap of two separate regions with masses ~ 11 Msun and 3 Msun corresponding to Thackeray 1A and Thackeray 1B, whereas the continuum dust emission with LABOCA 870 mum reveals an overall mass of ~ 19 Msun . The two regions are kinematically separated with velocities of -20 and -25 km s-1. The line survey reveals for the first time an unbiased view on the chemical molecular composition of these globules, with new detection of molecules such as C18O (2–1), H2CO(3 0,3 – 2 0,2 ), SO, HCN, HNC, HCO+, C2H and CS. MCweeds is used to constrain the column densities and abundances of these species. The incident FUV field intensity, G0 and hydrogen nucleus volume density n are estimated by using PDRTool box models constrained by observed CO line ratios. The data allows to investigate the stability of the globule by estimating their virial mass and ionization timescale. Both parameters confirm previous studies, including the HST image result, that the globule complex, Thackeray 1 is on the verge of breaking up or evaporating. [Referees: Prof. Dr. Karl Menten, Prof. Dr. Frank Bigiel]

	Main Colloquium
Prof. Cara Battersby	ORATED

University of Connecticut

Galaxy centers are the hubs of activity that drive galaxy evolution, from supermassive black holes to dense stellar clusters and feedback from newly-formed stars. Our own galaxy’s center has properties (densities, temperatures, and turbulent line widths) that are reminiscent of galaxies at the peak of cosmic star formation, but in our own cosmic backyard, where the interplay of these physical processes can be resolved in detail. In this talk, I will discuss gas inflow into our Galaxy’s Center, properties of the gas, and incipient star formation. I will discuss simulations of gas flows into the Galactic Center, which are thought to contribute to the unusual properties of star formation in this region, namely that it is producing 10 times fewer stars than predicted by standard scaling relations. I will describe observations of the gas and incipient star formation in this region, as well as discuss efforts to measure whether or not this unusual environment results in a change to the Initial Mass Function.

	Special Colloquium
Dr. Bryan Butler	ORATED

NRAO, Socorro, New Mexico, USA

Building on the remarkable success of the VLA, VLBA, and ALMA, NRAO is planning a large collecting area interferometer which will replace the VLA and VLBA - the next generation Very Large Array (ngVLA). For many of the same reasons that the VLA was constructed where it was (fraction of sky visible, quality of site, accessibility, etc.), the core and bulk of the collecting area of the ngVLA will be on the Plains of San Agustin, near where the center of the current VLA is. The ngVLA will have more than 10 times the sensitivity and spatial resolution of the VLA and ALMA, operating at frequencies from 1.2-116 GHz. The ngVLA will be optimized for observations at wavelengths between those of ALMA at mm-submm wavelengths, and the future SKA-1 at dm-m wavelengths, to be complementary to those instruments. The ngVLA will be transformative, with exquisite sensitivity to thermal line and continuum emission down to milliarcsecond resolution. The science goals are broad (a science book with more than 90 chapters and 285 unique authors has been written), but focus on: formation of planetary systems on terrestrial planet scales, including astrochemistry; characterization of galaxy structure and evolution; using pulsars in the Galactic center to test fundamental theories of gravity; and understanding the formation and evolution of stellar and supermassive black holes in the era of multi-messenger astronomy.

	Master Colloquium
Mahathi Chavali	ORATED

Max-Planck-Institut für Radioastronomie

Water is a key molecule to model the physics and chemistry of star formation. It is also the main constituent of icy grain mantles in the universe. We studied HDO and H2O transitions observed by the APEX telescope in the ATLASGAL TOP100 sample containing 110 clumps representing all evolutionary stages of high-mass star formation. We studied the ratio of HDO/H2O as the level of deuterium fractionation of a molecule is a good tracer of its formation process. H2-18O, an isotopologue of water is observed as a tracer for water, as water is difficult to observe from the ground. Water deuterium fractionation has been studied before, but not in such a large sample and range of evolutionary stages. The analysis is complicated by line blending with transitions from other molecules. We analysed these observations using the 1D radiative transfer code RATRAN to obtain the fractional abundances of HDO and H2O. Our studies show that the water deuterium fractionation values are about two orders of magnitude larger in star forming regions, compared to the elemental D/H ratio. [Referees: Prof. Dr. Karl Menten, Prof. Dr. Frank Bigiel]

	Special Colloquium
Prof. Adam Leroy	ORATED

Ohio State University, USA

I will present PHANGS-ALMA a multi-cycle ALMA survey of 90 nearby galaxies that offered our first real cloud-scale survey of molecular gas in galaxies. Stars form in giant molecular clouds, which are dense, cold condensations of gas that in many ways act as the engines of galaxy evolution. The demographics, evolution, and physical state of these clouds relate directly to how star formation proceeds, feedback operates, and galaxies grow. Until recently, however, we lacked any large survey that resolved the gas in galaxies into individual clouds. Leveraging ALMA's amazing combination of resolution, sensitivity, and mapping speed, PHANGS-ALMA mapped the CO 2-1 emission, our basic tracer of molecular gas in galaxies, at 1" = 50-150 pc resolution scales across essentially all accessible very nearby star-forming galaxies. On its own, PHANGS-ALMA resolves the molecular gas across whole galaxies into individual star-forming molecular clouds, giving access to the demographics and properties of tens of thousands of molecular clouds across a representative set of z=0 galaxies. When paired with large programs on VLT/MUSE, HST, ALMA mapping of high critical density lines, and soon JWST and MeerKAT, PHANGS offers a pan-chromatic view that breaks a representative sample of galaxies into individual star forming regions for the first time. I will give an overview of the motivation and execution of the survey, describe the data and products available to the community, and then highlight results on a few key topics - demographics, life cycles, and star formation properties of clouds - from the PHANGS team.

	Main Colloquium
Dr. Shane O'Sullivan	ORATED

Dublin City University

Radio galaxies can be observed throughout the majority of the history of the Universe and are thus excellent beacons for measuring the properties of the cosmic web and their evolution with cosmic time. Here I will highlight recent results from the ongoing LOFAR Two-metre Sky Survey (LoTSS), with a focus on the linear polarization and Faraday rotation measure (RM) data. The exceptional RM precision of LoTSS (< 0.1 rad/m2), in addition to unrivalled ancillary information such as the host galaxy redshift, has facilitated several new discoveries. For example, our recent detection of the RM signature from cosmic web filaments shows how LoTSS is transforming our understanding of cosmic magnetic fields, and providing a new way to study the properties of filaments and voids of the cosmic web in general.

	Special Colloquium
Various Panelists	ORATED

Event Horizon Telescope Collaboration

The Event Horizon Telescope (EHT) presented on May 12, 2022 the results from the observations of Sagittarius A* (Sgr A* ), the Galactic center source associated with a supermassive black hole. Those are based on observations conducted in 2017 with very-long-baseline interferometry operating at a wavelength of 1.3 mm. These results support an image dominated by a bright, thick ring with a diameter of about 52 microarcseconds, consistent with the appearance of a Kerr black hole with mass of 4 million solar masses. These results provide direct evidence for the presence of a supermassive black hole at the centre of the Milky Way. Details on these results will be provided in a series of short talks by MPIfR affiliated astronomers who are part of the EHT team, spanning over two hours including discussion: introduction by Anton Zensus and Karl Menten; followed by short presentations by Alan Roy, Michael Janssen, Eduardo Ros, Gunther Witzel, Christian M. Fromm, and Michael Kramer, concluding with a final discussion.

	Special Colloquium
Dr. Chiara Spiniello	ORATED

University of Oxford (UK)

Massive early-type galaxies (ETGs) are believed to form through a two-phase process: an intense and fast star formation episode creates red, compact, and massive objects (“red nuggets”), and then a second phase, dominated by mergers and gas inflows, causes structural evolution and size growth. Luckily, since merging is believed to be stochastic, a small fraction of red nuggets survives intact until the present-day Universe, without experiencing any further interaction: the so-called Relic Galaxies. These very old Ultra Compact Massive Galaxies (UCMGs) are made of “in situ only“ pristine stellar populations, and as such they provide a unique opportunity to track the formation of this specific galaxy stellar component, which is mixed with the accreted one in normal massive ETGs. In this talk I will first introduce our effort in obtaining a complete census of UCMGs at z between 0.1 and 0.5 from the Kilo Degree Survey, and then introduce the on-going INvestigating Stellar Population In RElics (INSPIRE) project which aims at building the first statistically large sample of confirmed relics. I will give few details on the target selection, observation, data analysis, strategies and results obtained in the INSPIRE Data Release 1, based on 19 systems for which observations were completed in 2020. In particular, I will present the kinematics and stellar population results and the relic confirmation for the biggest sample of spectroscopically confirmed relic galaxies currently available beyond the local universe. I will finally introduce some future perspectives and goals of INSPIRE, highlighting how relics can be used as powerful tools to study the early phases of massive galaxies formation.

	Special Colloquium
PD Dr. Silke Britzen	ORATED

MPIfR

Die Event-Horizon-Teleskop- (EHT) Kollaboration hat am 12. Mai das erste Bild vom Schatten des Schwarzen Lochs im Zentrum unserer Galaxie veröffentlicht. Es ist das erste Bild von Sgr A* , aber bereits das zweite Bild eines supermassereichen Schwarzen Lochs (nach M87* ). Mit einem Netzwerk von acht Radioteleskopen, das fast die Größe der Erde erreicht, gelang ein Bild, an dem auch viele Kollegen aus dem MPIfR lange gearbeitet haben. Ich berichte über die Entstehung dieses Bildes, die Unterschiede zwischen Sgr A* und M87* und die Bedeutung der Aufnahmen für die Erforschung dieser kosmischen Schwerkraftfallen. [Dieser Vortrag richtet sich an alle Mitarbeiter des Instituts]

	Special Colloquium
Dr. David Martı́nez Delgado	ORATED

Instituto de Astrofı́sica de Andalucı́a (CSIC), Spain

Within the hierarchical framework for galaxy formation, merging and tidal interactions are expected to shape large galaxies up to the present day. While major mergers are quite rare at present, minor mergers and satellite disruptions - that result in stellar streams - should be common, and are indeed seen in the stellar halos of the Milky Way and the Andromeda galaxy. In the last years, the Stellar Stream Legacy Survey (PI. Martinez-Delgado) has exploited available deep imaging of some nearby spiral galaxies with the ultimate aim of estimating the frequency, morphology and stellar luminosity/mass distribution of these structures in the local Universe. In this talk, I will present the current results of our systematic survey of stellar streams together with some recent follow-up observations (e.g. Megara, Subaru) and N-body modelling of the most striking streams. Finally, I will discuss what we can learn about galaxy formation from the results of this survey, including the comparison with the available L-CDM cosmological simulations.

	Main Colloquium
Prof. Simon Stellmer	ORATED

Physikalisches Institut der Universität Bonn

Astronomy and low-energy quantum physics experiments might seem to be located at opposite ends of the spectrum of physics research, but there are surprisingly many connections. I will elaborate on two of such topics. Firstly, I will present searches for beyond-standard-model physics based on precision spectroscopy. Secondly, I will advertise a new initiative to determine the Earth orientation parameters through a novel type of ring laser gyroscope.

	Special Colloquium
Dr. Tomás Cassanelli	ORATED

Departamento Ingeniería Eléctrica, Universidad de Chile, Santiago, Chile

The sensitivity of a radio telescope is of significant scientific interest. By increasing the sensitivity (or increasing the aperture efficiency) we are able to reduce errors in the telescope's main beam, and hence detect fainter sources. Out-of-focus (OOF) holography is a method to determine errors in the aperture plane of a radio telescope. In contrast to traditional holography, OOF can be applied without extra equipment and using common astronomical sources and receivers. By correcting aperture errors we are improving the surface accuracy, and effectively improving the aperture efficiency. In this talk I will describe the method, the developed software (pyoof), the observations, and how it is applied to the Effelsberg telescope. Results from multi-year observational campaigns will also be discussed, in an effort to model repeatable sources of deformation over the 100-m collector and improve its surface efficiency.

	SFB Colloquium
Prof. Brett McGuire	ORATED

Massachusetts Institute of Technology, Cambridge, USA

Polycyclic Aromatic Hydrocarbons (PAHs) have been implicated as a large reservoir of reactive carbon in the interstellar medium since the 1980s. PAHs have been widely attributed as the carriers of the unidentified infrared bands where their aggregate vibrational emission spectra are extremely well matched to the observed line signals. Only in the last year have individual PAHs been detected in the ISM for the first time, however, allowing us to begin to investigate the detailed chemical pathways for the formation and destruction of these molecules. In this talk, I will discuss our detections of PAH molecules via their rotational transitions using Green Bank Telescope observations of TMC-1 from the GOTHAM collaboration. I will discuss the efforts to model the chemistry of these PAHs, the necessity of complementary laboratory kinetics work, our application of novel machine learning approaches to exploring the chemical inventory in TMC-1, and finally the benefits of unbiased reaction screening studies in the laboratory with Microwave Spectral Taxonomy.

	Main Colloquium
Dr. Nami Sakai	ORATED

RIKEN Cluster for Pioneering Research, Saitama, Japan

Star and planet formation is one of the most fundamental structure-formation processes in the Universe. Physical processes of star and planet formation have widely been investigated as one of the major targets of astronomy and astrophysics by observations in all the wavelength region from radio to X-ray during the last few decades. Although a rough outline of these processes has been presented, there remain many unknowns and missing links. On the other hand, star and planet formation is a process where interstellar matter is evolved into planets. Hence exploring chemical evolution is of fundamental importance in understanding the origin of the Solar system, and eventually the origin of life on the Earth.  We have thus started to study the chemical evolution by collaborating with people in molecular science field. Such chemical approach also tells us novel information on physical processes of star and planet formation. In this talk, I will introduce efforts on such studies.

	Special Colloquium
Dr. Pierre Cox	ORATED

Institut d'Astrophysique de Paris, France

The Herschel surveys have enabled the detection of numerous dusty luminous sub-millimeter galaxies (SMGs) in the early universe. Follow-up observations of these sources are essential to determine their nature and the physical properties of their interstellar medium; reliable measurements of their redshifts are therefore crucial to explore the molecular and atomic gas of these objects. I will here present the results of a Large Program, z-GAL, using NOEMA, aimed at a comprehensive 3 and 2-mm spectroscopic redshift survey of a large (~140 sources) sample of the brightest (S500microm>80 mJy) SMGs selected from the Herschel H-ATLAS and HerMES surveys, which probe the peak of cosmic evolution (2

	Main Colloquium
Prof. Dominik Riechers	ORATED

Universität zu Köln

Recent years have seen great advances in studies of galaxy evolution and the early Universe due to substantial upgrades in our observational capabilities, coupled with ever more complex simulations of star, galaxy, and cosmic structure formation. I will highlight a range of new investigations of the cosmic baryon cycle coupling galaxies to their environments through their gas reservoirs, gas accretion, and outflows as a result of feedback processes driven by newly formed massive stars and active galactic nuclei. These properties evolve through cosmic history due to changes in the properties of "typical" galaxies and those undergoing their most intense phases of activity, but also due to changes in the environments resulting from the formation ever more pronounced cosmic structures and the cooling of the Universe due to cosmic expansion. I will introduce a new method to constrain the latter through direct line absorption against the cosmic microwave background, and promising new observational methods to constrain the former through large-scale line intensity mapping surveys of the early Universe, all the way back to cosmic reionization. Due to the rapid progress in observational, theoretical, and laboratory astronomy over the past decade, as well as new trends in astronomical instrumentation and facilities like CCAT-prime, ALMA 2030, NOEMA, the SKA and the ngVLA, we will have the tools to usher in a new phase in our understanding of the evolving cosmos back to its infancy stages in the coming decade.

	Special Colloquium
Dr. Carolina Casadio	ORATED

Institute of Astrophysics - FORTH, Heraklion, Greece

Projects aimed at characterising dark matter properties make use of very different approaches. One such approach is to look for strong gravitational lens systems. Gravitational lensed images with angular separation on milli-arcsecond scales probe gravitational lens systems where the lens is a compact object with mass in the range 10^6-10^9 solar masses, i.e. a supermassive compact object (SMCO). This mass range is particularly critical for the widely accepted cosmological model, which predicts many more DM halos on sub-galactic scales (< ~ 10^11 solar masses) than currently observed. The most direct way to explore these small angular scales is through the high-resolution of radio Very Long Baseline Interferometry (VLBI). We perform a pilot search, using the Astrogeo VLBI FITS image database and collecting multi-frequency, multi-epoch VLBI data of 13828 individual sources. We identified 40 milli-lens candidates, which have been followed-up with multi-frequency European VLBI Network (EVN) observations. Performing a similar search in a complete sample of ~ 5000 sources would allow us to constraint the abundance of SMCO in the Universe with more than an order of magnitude better precision than in previous studies, and to ultimately reject many currently viable DM models.

	Special Colloquium
Prof. Dr. Yuri Y. Kovalev	ORATED

Astro Space Center of Lebedev Phys. Inst. and Moscow Inst. of Phys. and Technology, Moscow, Russia

In this talk I will discuss recent developments in AGN studies on parsec and sub-parsec scales made with ground and Space VLBI as well with multi-band and multi-messenger observations. These include the extreme brightness temperature puzzle of RadioAstron measurements, the VLBI-Gaia view on the AGN disk-jet system, and the mounting observational indications for the blazar-neutrino connection. I will conclude the talk by outlining several exciting opportunities for centimeter and millimeter single-dish and VLBI experiments which will be playing a key role in the coming new era of multi-messenger astronomy.

	Main Colloquium
Dr. Guilaine Lagache	ORATED

Laboratoire d'Astrophysique de Marseille, Frankreich

CONCERTO is a new instrument that has just been successfully installed in the Cassegrain Cabin of the APEX telescope. It is a spectrometer with an instantaneous field of view exceeding 260 square arcminute and a spectral resolution up to 1.5 GHz. It covers the frequency band 130-310 GHz. The main scientific aim of CONCERTO is to map in 3D the fluctuations of the [CII] line intensity in the reionisation and post-reionisation epoch (z>5). This technique, known as intensity mapping, will allow us to address questions about the contribution of the dust-enshrouded star formation at z > 5, the history of metal enrichment, and the role of star-forming galaxies in shaping cosmic reionization. In addition to the main [CII] survey, we expect CONCERTO to bring a significant contribution in a number of areas, including the study of galaxy clusters (via the thermal and kinetic SZ effect), the follow-up of cosmological deep surveys, the observation of local galaxies, and the study of Galactic star-forming clouds. CONCERTO will also observe the CO intensity fluctuations arising from 0.3

	Main Colloquium
Dr. Eda Gjergo	ORATED

Wuhan University, China

The astrophysical sites which dominate the production of r-process elements have been a matter of contention for decades. The event GW170817/AT2017gfo, with the confirmed observation of the neutron-capture element strontium, originally raised hopes that neutron star mergers (NSM) could be a leading contributor to the production of heavy elements. However, galactic chemical evolution (GCE) models which take into account the rates of NSM events show that the onset of NSM occurs too late in the enrichment history to explain the abundance patterns of extremely metal poor stars. Among the other candidates is the small fraction of core-collapse supernovae whose progenitor star rotates sufficiently fast and creates magneto-hydrodynamic jets (MHDJ) capable of yielding r-process enrichment. It is possible that the rarity of such events may be offset by the larger rates and mass ejecta. After an introduction on GCE modeling, I will present results which include novel yield tabulations of neutron-capture events. I will explore the dependence of neutron-capture element abundances on theoretical NSM rates, as well as on future GW missions. We investigate some variation of parameters in single-zone GCE models for both the Milky Way and dwarf galaxies. On a s-process production baseline by AGB and core-collapse SNe, we estimate which conditions favor one r-process enrichment scenario over the other.

	Main Colloquium
Prof. Karl Mannheim	ORATED

Institut für Theoretische Physik und Astrophysik, Universität Würzburg

The plasma composition of jets ejected from accreting black holes in active galactic nuclei remains uncertain up to the present day. Inevitably, photon-photon pair production must lead to an excess of electron-positron pairs that remains unaccounted for in conventional single-fluid GRMHD simulations. Photon-photon pair production occurs in the virial plasma close to the ergosphere. Prolific pair production also results from particle acceleration throughout the jet. Multi-TeV gamma rays and the tentative associations of blazars with high-energy neutrinos and of radio galaxies with ultra-high energy cosmic rays require efficient acceleration of particles to ultra-high energies. Considerable efforts to encompass the kinetic processes responsible for the transport and acceleration of relativistic particles are currently undertaken to better understand how they shape the morphology and spectral energy distributions of jets. Studies of variability are key to understand the anisotropies associated with the acceleration processes and the stochastic nature of energy dissipation. Dissipation by kinetic processes resembles an exponential version of Ohmic dissipation in an electric wire.

	Main Colloquium
Prof. Sara Buson	CANCELED

Institut für Theoretische Physik und Astrophysik, Universität Würzburg

TBD

	Main Colloquium
Prof. Thiem Hoang	ORATED

Korea Astronomy and Space Science Institute, Daejeon, Republic of Korea

Dust is ubiquitous in the Universe and plays an important role in astrophysics. Dust grains are the building blocks of planets and catalytic surfaces for the formation of water and complex molecules. Dust polarization induced by the alignment of dust grains with the magnetic field is a powerful technique to observe cosmic magnetic fields and constrain dust properties. Dust grain size distribution determines star extinction and is a fundamental property for describing radiation pressure feedback from stars, supernova, and active galactic nuclei. In this talk, I shall show that grain’s suprathermal rotation plays a crucial role in dust astrophysics, determining grain alignment and affecting grain size distribution and surface chemistry. I shall first review the main physical mechanisms for grain alignment, including radiative torques and mechanical torques. I will then discuss the physics of rotational disruption of dust grains due to radiative torques, which implies the change of the dust properties with the local radiation field and density from the local medium to high-redshift galaxies. I will also discuss the new effects of suprathermal rotation on surface chemistry, radiation pressure feedback, and grain growth. Finally, I shall discuss a synergy of synthetic modeling with observations to test the new dust physical effects, probe dust properties, and measure magnetic fields in star-forming regions.

	Main Colloquium
Dr. Laura Kreidberg	ORATED

Max-Planck-Institut für Astronomie, Heidelberg

The past 25 years have revealed a diversity of exoplanets far beyond what was imagined from the limited sample in the Solar System. With new and upcoming observing facilities and a rapidly growing number of nearby planets, we are poised to bring this diversity into focus, with detailed follow-up characterization of the planets’ atmospheres. In this talk, I will discuss two frontier topics in exoplanet atmosphere studies: (1) what can we learn about giant planets' origins from their present-day atmospheres? and (2) what can we learn about habitability from “Earth cousins”, planets that are a little bigger or a little hotter than the Earth? Finally, I will conclude with my outlook on the search for biosignatures in the atmospheres of potentially inhabited planets.

	Main Colloquium
Prof. Anna Watts	ORATED

Astronomical Institute Anton Pannekoek, University of Amsterdam

NICER, the Neutron Star Interior Composition Explorer, is an X-ray telescope that was installed on the International Space Station in 2017. Its mission is to study the nature of the densest matter in the Universe, found in the cores of neutron stars. NICER uses Pulse Profile Modeling, a technique that exploits relativistic effects on X-rays emitted from the hot magnetic polar caps of millisecond pulsars. The technique also lets us map the hot emitting regions, which form as magnetospheric particles slam into the stellar surface. I will present NICER's latest results - including a measurement of the radius of the highest mass pulsar known - and discuss the implications for our understanding of ultradense matter, pulsar emission, and stellar magnetic fields. I will also look ahead to the next generation of X-ray telescopes that will exploit the Pulse Profile Modelling technique.

	Promotionskolloquium
Weiwei Chen	ORATED

Max-Planck-Institut für Radioastronomie

Fast transients are usually the products of rapid and enormous energy releases. To study the physical nature behind them, we must know the subtle temporal structure of the signal and where precisely they come from. However, some sporadic or even one-off fast radio transients have brought challenges to the current instruments. In this presentation, I describe the general beamforming technique, withwhich efficient wide-field, high time and spatial resolution survey can be achieved. Following that, I introduce the software package: MOSAIC developed for this project to provide the solutions to the challenges that come with this technique, such as the characterization of volatile beam shapes, the generation of efficient tiling of beams and the prediction of the evolution of the tiling through time. As an evaluation, a beamformed observation with MeerKAT on 47 Tucanae using the said techniques is presented and the localization capability with multiple beams is demonstrated. The performance of this beamforming platform has been further tested in numerous observations and surveys such as TRAPUM and MGPS that have yield significant results. I also report a search for giant pulses in selected pulsars. Many models try to explain the emission mechanism behind giant pulses from pulsars, some of which invoke the re-connection events near the light cylinder. In the meantime, a population of known giant pulse emitters shares similar properties, such as strong magnetic fields near the light cylinder and high energy emission. I select a couple of pulsars with these properties as candidates and observed them using the Effelsberg 100-meter telescope. A pipeline based on Heimdall was created to search giant pulses on the data and no credible detection was found. The conclusion for the non-detection is that these pulsars do not emit giant pulses which are detectable by our observation, or the high magnetic field strength near the light cylinder may not be a sufficient condition for the occurrence of giant pulses. [Referees: Prof. Dr. Michael Kramer, Prof. Dr. Frank Bertoldi, Prof. Dr. Ian Brock, Prof. Dr. Klaus Greve]

	Main Colloquium
Dr. Izaskun Jiménez-Serra	ORATED

Centro de Astrobiología, Madrid, Spain

In the past decade, Astrochemistry has witnessed an impressive increase in the number of detections of complex organic molecules. Some of these species are of prebiotic interest such as glycolaldehyde, the simplest sugar, or amino acetonitrile, a possible precursor of glycine. Recently, we have reported the detection of several new complex organic species in the interstellar medium, such as hydroxylamine and ethanolamine, known to be intermediate species in the formation processes of ribonucleotides and phospholipids within theories for the origin of life. In this talk, I will present our recent efforts to establish whether key precursors of prebiotic systems chemistry can be found in space. I will also analyse how chemical complexity builds up in the interstellar medium thanks to observations of the complex organic content in starless/pre-stellar cores, which represent the initial conditions of Solar-system formation.

	Main Colloquium
Dr. John Tobin	ORATED

National Radio Astronomy Observatory, Charlottesville, USA

The formation of disks and multiple star systems are integral parts of the star and planet formation process. Most stellar mass must be accreted through a disk, disks are the future sites of planet formation, and disks will also give rise to companion stars. Using ALMA and the VLA, we are conducting large continuum surveys of protostars (with molecular lines toward a subset of the full sample) in the nearby Perseus and Orion star-forming regions (with 20-30 au resolution) to characterize the disk radii, disk masses, and frequency of multiplicity throughout the protostellar phase. The molecular line data enable us to measure the masses of the protostars and we are beginning to identify and characterize the formation environments of both low and intermediate mass protostars. We find clear changes in multiplicity properties with evolution that link back to their formation mechanisms, establishing a foundation from which multiplicity evolution must begin.

	Informal Colloquium
Caroline Gieser	ORATED

Max-Planck-Institut für Astronomie, Heidelberg

During high-mass star formation, fragmentation takes place on various spatial scales from giant molecular clouds down to disk scales. At the earliest evolutionary stages, high-mass protostars are still deeply embedded within their parental molecular cloud and can be studied best at high spatial resolution with interferometers at mm wavelengths. The IRAM/NOEMA large program CORE allows us to analyze the physical and chemical properties of a sample of luminous high-mass star-forming regions. The 1 mm dust continuum of the sample shows a large diversity of fragmentation properties. Using the spectral line emission, we are able to determine the physical structure (temperature and density) and molecular content of individual fragmented cores. Even though all regions are classified to harbor high-mass protostellar objects, the molecular content shows a high degree of complexity. By combining the observed core properties, we are able to estimate chemical timescales with the physical-chemical model MUSCLE. We find well-constrained density and temperature profiles in agreement with theoretical predictions. The molecular complexity in the core spectra can be explained by an age spread that is then confirmed by our physical-chemical modeling. The hot molecular cores show the greatest number of emission lines, but we also find evolved cores in which most molecules are destroyed and, thus, the spectra appear line-poor once again. Currently, we are expanding our sample with ALMA 3 mm observations of 11 additional high-mass star-forming regions at different evolutionary stages - from infrared dark clouds to ultra-compact HII regions - in order to further investigate the evolution of the physical and chemical properties on core scales.

	Main Colloquium
Dr. Evan Keane	ORATED

National University of Ireland, Galway

Neutron stars exhibit many of the most extreme phenomena ever observed. They are also the most precise astrophysical tools in existence. Fortunately they are readily observable, across the electromagnetic spectrum, from Birr to Bonn to Boolardy. In this talk I will describe what is, and is not, known about neutron stars, with particular emphasis on the inter-related topics of their evolution post-supernova and pulsar emission physics. I will describe the difficulties involved in identifying evolutionary tracks for neutron stars, and discuss some potential solutions to these. Considering the growing number of diverse observational classes within the 'neutron star zoo' I will describe how these groups are, and are not, evolutionarily linked to one another. I will also describe search strategies that might identify the most interesting undiscovered sources.

	Promotionskolloquium
Vishnu Balakrishnan	ORATED

Max-Planck-Institut für Radioastronomie

Pulsars are rapidly rotating highly magnetised neutron stars that emit beams of electromagnetic radiation from their magnetic poles. These compact objects are unique as they are one of the densest forms of matter known in the Universe. Discovering pulsars are a gateway to new and exciting science as they have a wide range of scientific applications from studies of strong-field tests of gravity, neutron star physics and cosmology being a few examples. While all pulsars have their own applications, the bulk of my talk will concentrate on the techniques involved in finding new relativistic binary pulsars particularly the yet to be detected pulsar black-hole binary (PSR-BH) which can be used to test General Relativity and alternate theories of gravity in the quasi-stationary strong-field regime. As I will describe, in my thesis work I improved on our detection sensitivity towards PSR-BH binaries by a factor of 2-2.5 that was achieved purely by changing the search algorithm. I will present the results of my comprehensive search for recycled and unrecycled PSR-BH binaries in circular orbits in the High Time Resolution Universe South Low Latitude Survey (HTRU-S lowlat) using the template-bank algorithm. I will give details about the 20 new pulsars that were found from my searches including a new millisecond pulsar J1743−24 which is a rare intermediate spin-period pulsar in a 70.7-day orbit around a light companion star. Using our non-detections of PSR-BH binaries, I will also present limits on short orbital period PSR-BH binaries near the Galactic-Plane (|b| < 3.5 deg). I will also describe a novel Machine-learning (ML) pulsar candidate classifier using Semi-Supervised Generative Adversarial Networks (SGAN) which achieved better classification performance than the standard supervised algorithms commonly used in the literature using majority unlabelled datasets. Additionally, I will also present the results of the first fully coherent GPU-based radio pulsar search pipeline that can search across all five Keplerian parameters. We compare results from my pipeline to standard time and frequency domain acceleration and jerk search pipelines currently used in the literature. I will discuss its computational feasibility and the binary parameter spaces that have opened up that were previously not accessible. [Referees: Prof. Dr. Michael Kramer, Prof. Dr. Norbert Langer, Prof. Dr. Simon Stellmer, Prof. Dr. Volkmar Gieselmann]