Euclid: exploring the dark Universe

Main Colloquium
Prof. Henk Hoekstra
SCHEDULED
Leiden Observatory, the Netherlands

In past century we have learned much about the origin and evolution of the Universe. We now know the Universe is 13.8 billion years old, but its main ingredients remain a mystery: atoms make up only 5%. The rest consists of dark matter and dark energy, components for which we lack a fundamental physical theory. Better observations are needed to guide theory and ESA’s Euclid satellite is designed to do just that. Euclid is scheduled for launch in 2022 and will map the distribution of dark matter in the Universe as a function of cosmic time. However many challenges remain if we want to extract accurate cosmological information from these complex data.

TBD

Special Colloquium
Dr. Bernhard Schulz
SCHEDULED
Deutsches SOFIA Institut and NASA Ames Research Center

TBD

The early stages of stellar cluster formation: fragmentation of molecular clouds

Main Colloquium
Dr. Aina Palau
SCHEDULED
Instituto de Radioastronomía y Astrofísica, UNAM, Morelia, Mexico

How stellar clusters form and what determines their number of objects and stellar densities are long-standing questions, intimately related to the fragmentation properties of molecular clouds. It is thought that a number of properties of molecular clouds could influence and determine how clouds fragment. Some of these properties are the density and temperature structure, related to thermal support and gravity, turbulence, stellar feedback, initial angular momentum, and magnetic fields. In this talk I will present an observational campaign aimed at disentangling which of these properties finally control the fragmentation process in the dense parts of molecular clouds, from 0.2 to 0.005 pc scales. Special emphasis will be put on our latest result, a study of the relation between fragmentation and the magnetic field, where we observationally tested, for the first time in a statistically significant sample, the theoretical prediction that a strong magnetic field should suppress fragmentation.

The cloud-scale baryon cycle across the nearby galaxy population

Main Colloquium
Dr. Mélanie Chevance
SCHEDULED
Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg

The cycling of matter in galaxies between molecular clouds, stars and feedback is a major driver of galaxy evolution. However, it remains a major challenge to derive a theory of how galaxies turn their gas into stars and how stellar feedback affects the subsequent star formation on the cloud scale, as a function of the galactic environment. Star formation in galaxies is expected to be highly dependent on the galactic structure and dynamics, because it results from a competition between mechanisms such as gravitational collapse, shear, spiral arm passages, cloud-cloud collisions, and feedback processes such as supernovae, stellar winds, photoionization and radiation pressure. A statistically representative sample of galaxies is therefore needed to probe the wide range of conditions under which stars form. I will present the first systematic characterisation of the evolutionary timeline of the giant molecular cloud (GMC) lifecycle, star-formation and feedback in the PHANGS sample of star-forming disc galaxies. I will show that GMC are short-lived (10-30 Myr) and are dispersed after about one dynamical timescale by stellar feedback, between 1 and 5 Myr after massive stars emerge. Although the coupling efficiency of early feedback mechanisms such as photoionisation and stellar winds is limited to a few tens of percent, it is sufficient to disperse the parent molecular cloud prior to supernova explosions. This limits the integrated star formation efficiencies of GMCs to 2 to 10 per cent. These findings reveal that star formation in galaxies is fast and inefficient, and is governed by cloud-scale, environmentally-dependent, dynamical processes. These measurements constitute a fundamental test for numerical sub-grid recipes of star-formation and feedback in simulations of galaxy formation and evolution.

TBD

Special Colloquium
Prof. Abigail Vieregg
CANCELED
University of Chicago

TBD

Discovering the highest energy neutrinos with radio detectors

Special Colloquium
Prof. Abigail Vieregg
SCHEDULED
University of Chicago

The detection of high energy astrophysical neutrinos is an important step toward understanding the most energetic cosmic accelerators. IceCube, a large optical detector at the South Pole, has observed the first astrophysical neutrinos and identified at least one potential source. However, the best sensitivity at the highest energies comes from detectors that look for coherent radio Cherenkov emission from neutrino interactions. I will give an overview of the state of current experimental efforts, including recent results, and then discuss a suite of new experiments designed to discover neutrinos at the highest energies and push the energy threshold for radio detection down to overlap with the energy range probed by IceCube, thus covering the full astrophysical energy range out to the highest energies, and opening up new phase space for discovery. These include ground-based experiments such as RNO-G and IceCube-Gen2, as well as the balloon-borne experiment PUEO.