Correlating galaxy colour and halo concentration: A tunable Halo Model of galactic conformity

Understand

We extend the Halo Occupation Distribution (HOD) framework to generate mock galaxy catalogs exhibiting varying levels of "galactic conformity", which has emerged as a potentially powerful probe of environmental effects in galaxy evolution.

• Our model correlates galaxy colours in a group with the concentration of the common parent dark halo through a "group quenching efficiency" $\rho$ which makes older, more concentrated halos $\textit{at fixed mass}$ preferentially host redder galaxies.
• We find that, for a specific value of $\rho$, this 1-halo conformity matches corresponding measurements in a group catalog based on the Sloan Digital Sky Survey.
• Our mocks also display conformity at large separations from isolated objects, potentially an imprint of halo assembly bias.