Seminars and Colloquia at ESO Garching and on the campus

Significant observational data suggest a gas-rich major merger in the recent past (~2–3 Gyr ago) of our neighboring Andromeda galaxy (M31). The unusually high velocity dispersion of old stars in the disc, a burst of star formation ~2–3 Gyr ago, and conspicuous stellar substructures like the Giant Stellar Stream (GSS) in its inner halo, point to such a merger event. We utilize an N-body hydrodynamical simulation of a major merger (mass ratio of 1:4), which reproduces the main observational features of M31, to examine the nature of the substructures in its halo (GSS, NE-, and W-Shelves) and compare the model-estimated predictions with chemodynamical observations. Recently, data acquired with the Dark Energy Spectroscopic Instrument (DESI) revealed the presence of coherent (wedge-, chevron-, and stream-like) features in the phase space of stars within its major inner halo substructures and provided a large sample of spectroscopic [Fe/H] measurements for resolved stars. Our model succeeds in reproducing the observed metallicity values of the various substructures of M31. This then allows us to interpret some (still unexplained) observational traits of the galaxy, i.e., the multiple peaks and the corresponding gradient in the metallicity of stars within the GSS, as well as the various features in the phase space of its major stellar substructures. Leveraging the chemodynamical properties of M31's outskirts, we conclude that the GSS appears to be a superposition of multiple loops along the line-of-sight, responsible for the apparent coherent regions in the phase space of its stars. These discrete loops are shaped by consecutive pericentric passages of the satellite over the course of the major merger. 

For more than a century, Einstein’s General Relativity has transformed our understanding of the Universe, revealing that space and time together form a dynamic fabric that bends and stretches under the influence of gravity.
In this talk, I will take the audience on a journey through the history and key ideas of this remarkable theory, leading up to one of its most spectacular predictions: gravitational waves.

We will explore how Einstein’s equations foresee the existence of ripples in the fabric of spacetime—waves that travel across the cosmos—and how these elusive signals were first detected thanks to extraordinarily sensitive instruments.

After presenting some striking examples of astrophysical phenomena—such as the mergers of black holes and neutron stars—we will look ahead to the future of gravitational-wave astrophysics with LGWA (Lunar Gravitational Wave Antenna), a visionary project that aims to place a gravitational-wave detector on the surface of the Moon. LGWA promises to extend our ability to listen to the cosmos, unlocking realms of knowledge inaccessible from Earth—a bold scientific and technological challenge that marks the next great adventure in our quest to understand the Universe.

Polycyclic Aromatic Hydrocarbons (PAHs) are thought to sequester a large fraction (10-25%) of all carbon in the Universe.  While strong circumstantial evidence for their presence in space has existed since the 1980s, it is only in the last few years that the first individual PAH species have been definitively detected. In this talk, I'll describe the synthetic and spectroscopic laboratory work, computational approaches, and observational efforts which have led to these discoveries, discuss our current understanding of the formation and molecular evolution of PAHs in space, and describe the growing body of evidence that these species, in no small part, influence the inventory of raw organic material delivered to early planets.  I'll conclude by taking a critical look at open questions related to PAH chemistry in space and the prospects for the field going forward.

The PRobe far-Infrared Mission for Astrophysics (PRIMA) is a cold 1.8 meter space telescope designed to address key science objectives identified in Astro2020 and open significant discovery space for the astronomical community. With imaging and spectroscopic capabilities, PRIMA fills the order of magnitude gap in wavelength between the James Webb Space Telescope and the Atacama Large Millimeter Array which is rich with diagnostics tracers of the multi-phase gas and dust in a range of astronomical objects. PRIMA is one of two Probe concepts selected by NASA for a study in 2024/2025, potentially leading to implementation and launch in 2032. PRIMA was designed for a broad range of astrophysics, from how planets assemble their atmospheres to the coevolution of galaxies and black holes and the evolving properties of dust and metallicity over cosmic time. Seventy-five percent of PRIMA's observing time will be reserved for Guest Observer observations and all PI science data will also be available promptly for Guest Investigator science. In this talk, I will describe the PRIMA concept, instruments, introduce the main PI science topics, and discuss exciting opportunities for Guest Observer science.

Faint blazars are often difficult to identify, as their recognition typically requires cross-matching positional counterparts across radio, optical, and X-ray catalogs. To support high-energy studies for the Cherenkov Telescope Array Observatory (CTAO), we adopted an alternative approach. Starting from the Fermi-LAT 4FGL-DR4 catalog (5,062 γ-ray sources at galactic latitude |b| > 10°), we searched for blazar counterparts using Firmamento*, a web-based platform developed within the Open Universe initiative of UNOOSA. Firmamento integrates multi-frequency data and high-level analysis tools for spectral energy distribution (SED) studies.
By combining automated algorithms with visual inspection and validation by experts, high-school, and undergraduate students — given the large size of the sample — we discovered 421 new blazar associations, reducing the fraction of unassociated Fermi-LAT sources from 25% to 17%. The resulting catalog, 1FLAT, has been published in the Astrophysical Journal Supplement Series.
This talk presents both the scientific results and the educational framework behind this collaborative effort.

 

* https://firmamento.nyuad.nyu.edu/data_access