Informal Colloquium
Dr. Leonid Petrov	SCHEDULED

NASA Goddard Space Flight Center, USA

Processing the output of assimilation numerical weather models, one can derive the state of the atmosphere on a 4D grid. When we know the state of the atmosphere, we can compute path delay in the neutral atmosphere, atmospheric opacity, and brightness temperature of the atmosphere to a given station, given azimuth and elevation, and given moment of time. NASA Goddard Space Flight Center runs a suite of operational assimilation numerical weather model. In addition, NASA runs an operational service for computation of slant path delays, atmospheric opacities, and brightness temperatures. An overview of these data products will be given, and their use in data analysis will be discussed.

	Main Colloquium
Prof. Dr. Julia Tjus	SCHEDULED

RUB

Active galactic nuclei have long been discussed to be the sources of ultra-high-energy cosmic rays. The reason is simple: they are among the very few source classes that provide the right parameter range in terms of magnetic field strength and size that fulfill the necessary criterion for the acceleration to the highest observed cosmic-ray energy of 1e20eV. To prove this statement, or even to narrow down if the acceleration region sits in the inner jet, the termination show of the jet or the core is one of the major challenges in astro- and astroparticle physics. As cosmic-rays do not travel in straight lines, their directional information does not help for an anumbiguous identification. Iin this talk, it will be discussed how knowledge about the magnetic field structure and strength help to identify the origin of the acceleration zone and how we can use neutrinos to further pinpoint how active galaxies contribute to the cosmic ray spectrum.

	Promotionskolloquium
Timea Kovacs	SCHEDULED

MPIfR

Magnetic fields play an important role in galaxy evolution, from processes such as gas dynamics and star formation to galactic outflows. However, the redshift evolution of galactic-scale magnetic fields is not well constrained, both observations and theoretical predictions are lacking, with only a handful of direct magnetic field strength measurements in distant galaxies. In my talk, I will present my results from both radio polarimetric observations and synthetic observations made with the IllustrisTNG50 simulation. First, I will present the analysis of broadband (1 - 8 GHz) spectro-polarimetric Very Large Array observations of two lensing systems (B1600+434 and B0218+357). Using these, we measured the halo magnetic field of a distant galaxy at z=0.414 (corresponding to 4.4 Gyr ago) for the first time with a strength of 1.2 - 1.8 uG, and found an axisymmetric disk field of 2 - 20 uG in a lensing galaxy at z=0.685 (6.3 Gyr ago), in agreement with the magnetic field strength and structure of nearby galaxies. Then, I will show how the observables of magnetic fields evolve over redshift using 16 500 galaxies at redshifts of 0 < z < 2 from the state-of-the-art cosmological magneto-hydrodynamic simulation IllustrisTNG50. I explore two methods used to obtain cosmic magnetic field strengths: deriving the magnetic field strength of intervening galaxies in front of polarized background quasars and deriving the magnetic field strength of the IGM by utilizing FRBs. In the near future, we expect the number of known lensing systems, quasars with intervening galaxies, and polarized FRBs to dramatically increase by tens of thousands of systems due to new radio surveys and telescopes. The results I am presenting demonstrate how the lensing method can be applied to different galaxies, and predict measuring the magnetic field strength of the IGM with a 2 rad m^-2 precision using FRBs will be possible in under 10 years.

	Lunch Colloquium
Dr. Mark Walker	SCHEDULED

Manly Astrophysics, Australia

In astronomy, solid hydrogen has been largely ignored for over 50 years. That was a mistake. It came about because the pure solid was shown to sublimate rapidly under interstellar conditions; but in the ISM solid H2 is expected to become electrically charged, and the electric field suppresses sublimation. I will argue that the spectroscopic properties of interstellar dust make a strong case in support of solid H2 being a major dust component. In turn, that suggests that our Galaxy possesses a substantial reservoir of dark gas clouds - hydrogen "snow clouds". I'll describe a new picture of the physics of interstellar scattering of radio waves, based on the tidal disruption of H2 "snow clouds" by stars. Somewhat surprisingly, that work has also led us to a beautiful new model of the rare, but spectacular, R Coronae Borealis stars.

	Special Colloquium
Prof. Dr. Bhaswati Mookerjea	SCHEDULED

Tata Institute of Fundamental Research (TIFR)

The Space Applications Centre (SAC) of the Indian Space Research Organization (ISRO) has successfully designed and developed the critical components for the first Indian sub-millimeter telescope. The observatory will be located initially at the 4500 m Hanle site of the Indian Astronomical Observatory and will be a partnership of ISRO withe Indian Sub-millimeter-wave Astronomy Alliance, which is a partnership of scientists from leading Indian astronomy, physics and space research institutions. The 6-m telescope in the first phase will be equipped with a dual band receiver at 230--345 GHz and will be used for the studies of the neutral interstellar medium. The observatory by virtue of its longitudinal position has the potential to be a new location for the Event Horizon Telescope (EHT). The Himalayan sites are among a small number locations globally, that have sufficient atmospheric transmission to allow observations in the sub-millimeter wavelength bands, at frequencies of about 200-500 GHz and higher. In this talk, I will present the current status of the Indian sub-millimeter observatory as well as the ongoing and future work on the characterization of the Himalayan sites for sub-millimeter astronomy.

	Main Colloquium
Prof. Thorsten Kleine	SCHEDULED

Max Planck Institute for Solar System Research

TBD