S17
Galaxy evolution in the faint Universe: insights from the era of large surveys
Communauté
Contact : es2074@cam.ac.uk
Main language for discussions / Langue principale des échanges oraux : ENGLISH
In the ΛCDM paradigm, galaxies and their dark matter haloes assemble hierarchically through continuous dark matter and gas accretion along a series of mergers. These events leave behind long-lived imprints—extended stellar haloes, tidal debris, streams and remnant faint satellite galaxies, intracluster light (ICL) —that trace the dynamical history of galaxy formation. Studying these low surface brightness (LSB) structures provides a powerful way to (i) probe the nature of dark matter, (ii) constrain the physics of galaxy growth, and (iii) uncover the assembly histories of galaxies across mass and environment.
Within the Local Group, resolved stellar populations studies using the synergy between Gaia and spectroscopic surveys such as LAMOST, APOGEE, and the upcoming WEAVE and 4MOST are yielding a detailed characterisation of stellar populations and kinematics in dwarf galaxies and stellar streams, offering direct constraints on dark matter halo structure and merger events. These nearby benchmarks set the stage for interpreting fainter, more distant structures and for testing cosmological simulations.
Beyond the Local Group, studying LSB structures has long been hindered by their faint, unresolved diffuse nature. However, in the past decade recent advances in instrumentation, data processing, and analysis techniques have begun to lift this barrier, enabling the detection of faint tidal features, stellar haloes, dwarf galaxies and intracluster light that encode the complex formation histories of galaxies. Today, the advent of deep, wide-field surveys such as Euclid and Rubin/LSST represent a transformative leap, providing for the first time homogeneous, multi-wavelength imaging from optical to near-infrared across vast regions of the sky. This new era makes it possible to conduct systematic statistical studies of LSB structures across a broad range of redshifts, masses, and environments. Looking ahead, upcoming missions and facilities, including Roman, ARRAKIHS, MESSIER, and ELT-class spectrographs, promise to further expand the frontier of LSB science in depth, resolution, and spectral coverage.
These advances raise important new questions:
- To what extent can tidal features and dwarf populations trace the late-time mass assembly of galaxies?
- How do tidal debris and dwarf galaxies constrain the shapes and substructures of the gravitational potentials of dark matter haloes?
- Which tools, observational and theoretical, are required to fully extract physical insights from this faint Universe?
- How can we trace the origin and assembly history of the ICL, and how does this inform our understanding of the global evolution of galaxy populations in clusters?
Answering these questions requires (i) dedicated methodologies, from automated detection pipelines to tackle the growing deluge of data, (ii) dedicated analysis techniques, (iii) population-level statistical tools, and (iv) synthetic mock observations from simulations. These, in turn, require robust theoretical inputs to connect observed morphologies to the underlying physical processes that shape them.
This session will bring together the French community working on the LSB Universe—from resolved stellar populations in the Local Group to the analysis of deep imaging data in the nearby Universe. We aim to showcase recent observational and theoretical advances, foster cross-fertilisation across redshift and wavelength regimes, and prepare for the challenges and opportunities that new LSB surveys present. By uniting efforts across simulations, observations, and data science, this session will help define the future of galaxy formation studies at the faintest limits of detectability.
SOC: Elisabeth Sola (es2074@cam.ac.uk) & David Valls-Gabaud (david.valls-gabaud@obspm.fr)