The massive end of the luminosity and stellar mass functions and clustering from CMASS to SDSS: Evidence for and against passive evolution

TL;DR

This study analyzes the luminosity and stellar mass functions of CMASS galaxies at z ~ 0.55, revealing that while passive evolution models fit some data, clustering differences challenge this scenario, emphasizing the importance of combined measurements.

Contribution

It provides a revised luminosity function based on Sersic fits and critically assesses passive evolution models using clustering and number density comparisons.

Findings

Sersic-based photometry suggests more luminous, massive galaxies than previous estimates.

Passive evolution models fit the luminosity and mass functions if assuming old stellar ages.

Clustering data contradict passive evolution, indicating additional processes like mergers are involved.

Abstract

We describe the luminosity function, based on Sersic fits to the light profiles, of CMASS galaxies at z ~ 0.55. Compared to previous estimates, our Sersic-based reductions imply more luminous, massive galaxies, consistent with the effects of Sersic- rather than Petrosian or de Vaucouleur-based photometry on the Sloan Digital Sky Survey (SDSS) main galaxy sample at z ~ 0.1. This implies a significant revision of the high mass end of the correlation between stellar and halo mass. Inferences about the evolution of the luminosity and stellar mass functions depend strongly on the assumed, and uncertain, k+e corrections. In turn, these depend on the assumed age of the population. Applying k+e corrections taken from fitting the models of Maraston et al. (2009) to the colors of both SDSS and CMASS galaxies, the evolution of the luminosity and stellar mass functions appears impressively passive, provided that the fits are required to return old ages. However, when matched in comoving number- or luminosity-density, the SDSS galaxies are less strongly clustered compared to their counterparts in CMASS. This rules out the passive evolution scenario, and, indeed, any minor merger scenarios which preserve the rank ordering in stellar mass of the population. Potential incompletenesses in the CMASS sample would further enhance this mismatch. Our analysis highlights the virtue of combining clustering measurements with number counts.