The Stellar Halos of Galaxies and Outskirts of Galaxy Clusters: Clues to their Accretion History

Understanding mass assembly at different scales is key to improving our knowledge on galaxy formation and evolution in general. Stellar halos of galaxies, primarily formed through the accretion and merger of smaller objects, preserve memory of their assembly history, offering unique insight into the accretion and mass growth history of galaxies. During the last decade there has been significant progress, both from the observational and numerical side, to characterize stellar halos of Milky Way-mass galaxies. And more recently the outskirts of low-mass galaxies have also started to be explored. On the high mass end, outskirts of galaxy clusters are also important observational probes of how these systems grow in a cosmological context and can provide insights into their accretion history.

In this talk, I will present the main results both from observations and cosmological simulations that allow us to link the observed properties of stellar halos with the accretion history of their host galaxies. Additionally, I will present the first kinematical measurement of a diffuse stellar halo beyond the Local Group, the stellar halo of the edge-on galaxy NGC 4945, using a novel technique. We couple new deep MUSE spectroscopic observations with existing HST imaging data to spectroscopically measure the radial line-of-sight heliocentric velocity and velocity dispersion in a field at 40 kpc (stellar halo field) along NGC 4945 major axis. If time permits, I will introduce the 4MOST/CHANCES survey, aimed at observing the outskirts of ~150 galaxy clusters.

Fecha y lugar: 16/10/2025 – 12:30 | Salón de Actos
Antonela Monachesi
Universidad de La Serena, Chile