Red dwarfs and nearby terrestrial planets: discovery and opportunities

Main Colloquium
Dr. Guillem Anglada-Escudé
SCHEDULED
Institut de Ciencies de l'Espai-CSIC, Institut d'Estudis Espacials de Catalunya, Barcelona, Spain

Red dwarfs, which are stars that are typically born with masses below 0.6 Msun, are the most numerous stars, and comprise about 70% of the stellar population in the Solar neighborhood. Because we rely on indirect methods for detection of exoplanets, this stars provide a number of advantages for the detection of the smallest planets to the point that today we can detect planets with bulk properties and equilibrium temperatures similar to Earth around them. The detection method strongly influences the possible characterization methods and the information that can be achieved. Irrespective of the technique, the nearest stars and their planets are the ones providing best changes for characterizing their atmospheres and searching for evidence for life. I will review the state of the art for exoplanet detection around the nearest stars, and describe the methods and characterisation opportunities that these planets offer.

New Insights into the Milky Way Magnetic Fields through Radio Broadband Spectro-polarimetry

Promotionskolloquium
Yik Ki Ma
SCHEDULED
Max-Planck-Institut für Radioastronomie

Magnetic field is an essential ingredient of the interstellar medium of galaxies. An accurate characterisation of the magnetic field strength and structure of the Milky Way is crucial for complete understanding of many Galactic astrophysical processes. The Faraday rotation effect can be exploited to reveal the strength and direction of the magnetic field component parallel to the line of sight, which are imprinted in the rotation measure (RM) values obtained from radio polarisation observations. In my thesis, I utilised the broadband spectro-polarimetric capability of the Karl G. Jansky Very Large Array (VLA) in L-band (1-2 GHz) to gain new insights into the magnetic fields of the Milky Way in two ways. Firstly, I investigated in the reliability of the NRAO VLA Sky Survey (NVSS) RM catalogue, which is indispensable for the modelling of the global Milky Way magnetic field. In particular, I quantified the effects of npi-ambiguity and off-axis instrumental polarisation on the RM catalogue, and unlocked the full potential of the NVSS RM catalogue for careful studies of Galactic magnetism. Secondly, I performed new radio observations for a direct study of the magnetic fields near the Milky Way mid-plane in the first Galactic quadrant. My new observations led to a drastic increase in the number of reliable RM values by a factor of five in the target sky region. From the new data, I discovered new features in the Galactic magneto-ionic medium, with important implications on the magnetic field ordering mechanism of galaxies. [Referees: Prof. Dr. Michael Kramer, Prof. Dr. Pavel Kroupa, Prof. Dr. Klaus Desch, Prof. Dr. Dietmar Quandt]

Mapping the Ionized ISM in Nearby Galaxies

SFB Colloquium
Dr. Kathryn Kreckel
SCHEDULED
Astronomisches Rechen-Institut, Universität Heidelberg, Germany

The ionized interstellar medium (ISM) provides crucial insights into understanding baryon cycling within disk galaxies and tracing radiative and mechanical feedback from young massive stars. With new VLT/MUSE optical integral field spectroscopy, the PHANGS team now has a wealth of emission line maps that trace different ionization sources and physical conditions across nearby disk galaxies at the 50 pc spatial scales needed to isolate individual ionized regions (e.g. HII regions, supernova remnants, planetary nebulae) from surrounding diffuse ionized gas. I will present our most recent results connecting the molecular gas with observed sites of massive star formation, and measuring the gas phase oxygen abundances across thousands of HII regions. Within the context of the large scale galactic environment, these studies have implications for our understanding of how spiral structure acts to organize and mix the ISM, and regulate star formation.

Worlds near and far: mapping the state of the Solar System

Special Colloquium
Dr. Michele Bannister
SCHEDULED
Queen's University Belfast

The small bodies of planetary systems record how their systems formed and evolved. Major observational surveys including Pan-STARRS and OSSOS are providing new insight into the physical properties and orbits in both the inner and the outer Solar System. Together with colour measurements of small-body surfaces, it is finally possible to start piecing together the original compositional structure of our protoplanetary disk, even after the scattering from planetary migration that emplaced today’s intricate dynamical structures. New discoveries of interstellar objects mean the compositions of planetesimals from other stars can now be directly compared to those of our local populations. The prospects for discoveries with the next-generation survey facility, the Large Synoptic Survey Telescope, are bright.

Neutral gas outflows in luminous galaxies at low and high redshift

Main Colloquium
Prof. Paul van der Werf
SCHEDULED
Leiden Observatory, The Netherlands

Galaxies are not closed boxes. They feed on gas inflow from the cosmic web; conversely, feedback-driven gas outflows remove gas from galaxies again, either temporarily or definitively. The last decade has seen an explosion (no pun intended) in observations of gaseous outflows. These outflows are complex, containing ionized, neutral atomic and molecular components, and come in many types, from small but highly collimated and dense molecular jets to enormous ionized gas halos. I will focus on outflows of two types: compact molecular jets emanating from deeply obscured galactic nuclei, and wide-angle outflows traced by P-Cygni profiles of molecular lines. The latter form outstanding probes of neutral outflows in high-redshift galaxies. I will discuss one example in detail, where we trace the outflow in a redshift 2 galaxy using OH+ as a kinematic tracer. In addition to tracing the outflow parameters, this reveals local conditions and chemistry in the outflowing gas.