The galaxy clustering crisis in abundance matching

Galaxy clustering on small scales is significantly underpredicted by sub-halo abundance matching (SHAM) models that populate (sub-)haloes with galaxies based on peak halo mass, M_peak. SHAM models based on the peak maximum circular velocity, V_peak, have had much better success. The primary reason for M_peak-based models fail is the relatively low abundance of satellite galaxies produced in these models compared to those based on V_peak. Despite success in predicting clustering, a simple V_peak-based SHAM model results in predictions for galaxy growth that are at odds with observations. We evaluate three possible remedies that could 'save' mass-based SHAM: (1) SHAM models require a significant population of 'orphan' galaxies as a result of artificial disruption/merging of sub-haloes in modern high-resolution dark matter simulations; (2) satellites must grow significantly after their accretion; and (3) stellar mass is significantly affected by halo assembly history. No solution is entirely satisfactory. However, regardless of the particulars, we show that popular SHAM models based on M_peak cannot be complete physical models as presented. Either V_peak truly is a better predictor of stellar mass at z ~ 0 and it remains to be seen how the correlation between stellar mass and V_peak comes about, or SHAM models are missing vital component(s) that significantly affect galaxy clustering.