Abstract

Contributed Talk - Splinter Galaxies

Friday, 11 September 2026, 15:00   (MW-0250)

The distribution of different star-forming galaxies in dense environments

Eileen Herwig
Max Planck Institute for Astrophysics

At z~2–4, galaxy protoclusters are expected to undergo most of their assembly through star formation extending across scales of several megaparsecs. Although dusty starbursts in rare, massive submillimeter galaxies (SMGs) are often associated with the densest regions, the bulk of star formation is thought to occur in smaller, UV-bright main-sequence galaxies. A complete census of the star-forming activity in assembling protoclusters therefore requires multiple complementary tracers. We target a field at z=3.2 hosting multiple AGNs at its center that is known to be exceptionally overdense in SMGs. Our observations cover a field of view spanning several megaparsecs, comparable to the expected extent of galaxy protoclusters at these redshifts. We combine SCUBA-2 observations of the 850 micron continuum, ALMA spectroscopy of the CO(4-3) transition, and FORS2 imaging to photometrically identify UV-bright galaxies using the Lyman-break technique and narrowband Lyα excess selection. Using these complementary datasets, we compare the spatial distribution of the different galaxy populations, assess their respective contributions to the total star formation rate, and investigate the filamentary network feeding the central overdensity and sustaining its extreme activity. By connecting the obscured and unobscured components of the star-forming galaxy population, this multi-wavelength approach provides a more complete view of how the most massive structures in the Universe assemble.