COSMOS-Web: does halo mass alone shape the clustering of star-forming and quiescent galaxies?

Abstract

While stellar mass correlates strongly with halo mass, it remains unclear whether halo mass alone governs galaxy star-formation activity, or whether secondary halo properties and environment also play a role. We investigate these effects beyond halo mass by measuring the auto- and cross-correlations of star-forming and quiescent galaxies in the COSMOS-Web survey from $z=5$ to the present day. To isolate environmental contributions, we introduce a method that matches the halo mass distributions of both populations using the UniverseMachine model. We find that quiescent galaxies remain more strongly clustered than star-forming systems by at least $0.5-1$ dex at all redshifts, even after controlling for halo mass. At $z\le 2$, this excess clustering increases towards lower stellar masses, with the most clustered objects being $\log (M_{\star }/{\mathrm{M}}_{\odot })\le 9.5$ quiescent galaxies. This points to environmental quenching significantly affecting low-mass galaxies at $z\le 2$, likely driven by ram-pressure stripping or the suppression of cold gas accretion, as these objects show disky morphologies. Cross-correlations further reveal one-halo conformity up to $z\simeq 2$: low-mass (or satellite) quiescent galaxies are more strongly clustered around massive (or central) quiescent galaxies than around star-forming centrals of the same halo mass. This signal may arise from quenching mechanisms affecting both centrals and satellites, correlated assembly histories prior to infall, or dependencies on secondary halo properties. Both environmental quenching and conformity appear to vanish between $z\simeq 5$ and $2$. Together, these results challenge the common assumption that clustering and star-formation activity depend solely on halo mass.

12 pages, 8 figures. Submitted to A&A