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

	Special Colloquium
Prof. Dr. Tom Megeath	SCHEDULED

The University of Toledo

TBD

	Main Colloquium
Prof. Dr. Selma de Mink	CANCELED

MPA

+++postponed+++

	Main Colloquium
Dr. Jaques Roland	SCHEDULED

Observatoire de Paris

Variations of the flux density of the nucleus of an extragalactic radio source can be due either to the variations of the synchrotron spectra of the black holes contained in the nucleus, or to the ejection of VLBI components. As a consequence of the variations of the synchrotron spectra of the black holes, there will be periods during which the low frequency and the high frequency observations will be aligned on the same BH, say BH1, and periods during which the low frequency and the high frequency observations will be aligned on different BHs, say BH1 and BH2. We obtained centroid position time series at 15 GHz from MOJAVE modelfitting giving epoch positions of the VLBI components and for each epoch, we calculated the 15~GHz flux barycenter positions using a beam $B = 2$ mas which corresponds to the $8$~GHz beam. The comparison of the $8$~GHz and $15$~GHz time series shows that: a) the time series are generally correlated, but they can be anti-correlated during some periods and b) the absolute position of the ICRF3 survey corresponds to the mean position of the $15$~GHz flux density barycenter within $\leq 0.100$ mas$. The comparison of the $8$ and $15$~GHz has been done for 2201+315 which structure of the nucleus is known and for 0851+202 and 0923+392 which structures of the nucleus are not known.

	Main Colloquium
Prof. Heinz Andernach	SCHEDULED

University of Guanajuato

TBD

	Main Colloquium
Prof. Dr. Leon Koopmans	SCHEDULED

Groningen University

Observations of the first luminous cosmic structures, with ground and space-based optical and infrared telescopes, are slowly lifting the veil on the complex physical processes that governed the Epoch of Reionization and Cosmic Dawn. These observations, most recently with JWST reaching redshift well into the Cosmic Dawn, however, are only the tip of the iceberg: islands in a sea of neutral hydrogen. I will review the current status of the LOFAR Epoch of Reionization Key-Science Program, presenting our latest improved power-spectrum limits on the 21-cm signal of neutral hydrogen, the constraints it sets on the high-redshift IGM, and present several breakthroughs in our understanding of the data itself, which will be crucial for the future SKA. I will also show the latest results from the NenuFAR Cosmic Dawn Key-Science Program, which aims to measure the 21-cm signal during the Cosmic Dawn. I will place these results in context of SKA and our plans to push towards 21-cm cosmology of the Dark Ages using space-based receivers, such as ALO, currently a pre-phase-A concept for a radio telescope to be placed on the lunar farside by ESA's Argonaut landers.

	Main Colloquium
Dr. Sergei Tsygankov	SCHEDULED

Turku University

TBD

	Special Colloquium
Prof. Richard Lieu	SCHEDULED

University of Alabama in Huntsville

TBD

	Promotionskolloquium
Jonah Wagenveld	SCHEDULED

MPIfR

The cosmic radio dipole is an anisotropy in the number counts of radio sources, analogous to the dipole seen in the cosmic microwave background (CMB). Measurements of the radio dipole with large radio surveys have shown that though the radio dipole is aligned in direction with the CMB dipole, the amplitudes are in tension. These observations present an intriguing puzzle as to the cause of this discrepancy, with a true anisotropy having large repercussions for cosmology as a whole. Measurements of the cosmic radio dipole with large radio surveys have often suffered from systematics in the data, hampering sensitivity and reliability of these measurements. In this thesis, I aim to measure the cosmic radio dipole with the MeerKAT Absorption Line Survey (MALS). Though sky coverage of MALS is low, with 391 pointings observed in total, the sensitivity and field of view of MeerKAT yields thousands of sources observed in each pointing. We perform a deep analysis of the complete set of processing steps, from observations to cataloguing, of ten MALS pointings, to characterise and quantify potential systematic effects which could hamper a dipole measurement. Using the noise characteristics of these pointings, we find that we can homogenise the catalogues to a deep enough level for a dipole measurement. We furthermore define Bayesian estimators that are able to perform a dipole measurement with the sparse sky coverage of MALS. Testing these estimators out on other radio surveys, we perform the most significant measurement of the cosmic radio dipole yet. Finally, we perform a measurement of the dipole using all MALS pointings, but find an effect in the data which causes a systematic variation in source density with declination, hampering a dipole measurement. Though we can account for the effect by extending our estimators, it comes at the cost of further uncertainties, which can only be remedied by reprocessing the data. However, combined with other measurements performed in this thesis and in the literature, there is a little doubt anymore as to the legitimacy of the radio dipole measurement, and we may look forward to further measurements which aim to uncover the cause of the dipole tension.

	Main Colloquium
Prof. Dr. Selma de Mink	SCHEDULED

MPA

TBD

	Main Colloquium
Dr. Roberto Neri	SCHEDULED

IRAM Grenoble (France)

TBD

	Main Colloquium
Prof. Dr. Felix Aharonian	CANCELED

DIAS/Dublin and MPIK/Heidelberg

TBD

	Main Colloquium
Prof. Dr. Felix Aharonian	SCHEDULED

DIAS/Dublin and MPIK/Heidelberg

TBD