Seminars and Colloquia at ESO Santiago

Since the 1980s, the discovery of the "Great Attractor" has led to the dynamics of the Galaxy, the Local Group and cluster, being considered as being subject to gravitational effects modifying the Hubble flow. Over the years, numerous studies have been conducted to locate and estimate the topology, mass, and nature of this enormous concentration of matter. At the turn of the 21st century, the results obtained have made it possible to approximate its characteristics which are located well beyond the Hydra-Centaurus Supercluster. 
We review the most recent results obtained, in particular through the analysis of surrounding galaxy clusters and by determining the properties of clusters close to the galactic plane. 

The weakness of the hyperfine 21cm line, the main tracer of the atomic gas content of galaxies, has meant that we know little about the HI mass of high-redshift galaxies and its evolution. This has long been one of the biggest lacunae in our understanding of galaxy evolution. ``Stacking'' of the 21cm emission signals from a large sample of high-redshift galaxies, with known optical positions and redshifs and observed simultaneously with a radio interferometer, can allow one to determine the atomic gas properties of the galaxy population. The advent of new or upgraded radio interferometers, with wideband spectral capabilities and modern correlators, has recently yielded dramatic progress in this field. In this talk, I will describe the state of the art in such 21cm stacking experiments from deep studies with the Giant Metrewave Radio Telescope that have yielded the first measurements of the atomic gas properties of star-forming galaxies during the era of cosmic noon.

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Gamma-ray bursts fascinate astronomers both for their astounding power and for their effectiveness as cosmological probes. Spectroscopy of their bright optical counterparts allows to dissect the interstellar and circumgalactic medium of high-redshift star-forming galaxies, testing their gas, metals, dust, and molecular content. At the same time, also thanks to a new suite of instruments, we have been discovering a richer diversity of progenitor systems - with the two main players being collapsing massive stars and binary compact object mergers. I will highlight the recent progress and surprises in the field achieved via the "Stargate" program at the VLT.

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