Kavli Affiliate: Risa H. Wechsler
| First 5 Authors: Sihan Yuan, Risa H. Wechsler, Yunchong Wang, Mithi A. C. de los Reyes, Justin Myles
| Summary:
Emission line galaxies (ELGs) are now the preeminent tracers of large-scale
structure at z>0.8 due to their high density and strong emission lines, which
enable accurate redshift measurements. However, relatively little is known
about ELG evolution and the ELG-halo connection, exposing us to potential
modeling systematics in cosmology inference using these sources. In this paper,
we propose a physical picture of ELGs and improve ELG-halo connection modeling
using a variety of observations and simulated galaxy models. We investigate
DESI-selected ELGs in COSMOS data, and infer that ELGs are rapidly star-forming
galaxies with a large fraction exhibiting disturbed morphology, implying that
many of them are likely to be merger-driven starbursts. We further postulate
that the tidal interactions from mergers lead to correlated star formation in
central-satellite ELG pairs, a phenomenon dubbed "conformity." We argue for the
need to include conformity in the ELG-halo connection using galaxy models such
as IllustrisTNG, and by combining observations such as the DESI ELG
auto-correlation, ELG cross-correlation with Luminous Red Galaxies (LRGs), and
ELG-cluster cross-correlation. We also explore the origin of conformity using
the UniverseMachine model and elucidate the difference between conformity and
the well-known galaxy assembly bias effect.
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