Using Maximum Circular Velocity in Halo Occupation Distribution Models to Predict Galaxy Clustering

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Abstract

Standard halo occupation distribution (HOD) models predict how galaxies occupy halos based on a single property, the virial mass, M _vir. To incorporate galaxy assembly bias, we consider alternative halo mass proxies to use in the HOD. A promising replacement is maximum circular velocity, ${V}_{\max }$ , which measures the halo's potential well, and successfully predicts galaxy clustering in subhalo abundance matching models. We fit galaxy clustering measurements from SDSS DR7 with two modified HODs besides the standard M _vir-based model: one where ${V}_{\max }$ is used as the halo property that determines galaxy occupation, and the other adopting an adjustable combination of M _vir and ${V}_{\max }$ . Except for the reduced volume M _r < - 20 threshold sample fit with ${V}_{\max }$ alone, neither change improves the model performance in predicting the projected two-point correlation function, w _p. We conclude that switching the primary variable to ${V}_{\max }$ does not significantly improve the HOD model's ability to fit galaxy clustering.