A Steep Slope and Small Scatter for the High-Mass End of the L-$\sigma$ Relation at $z\sim0.55$

TL;DR

This study precisely measures the high-mass end of the L-$\sigma$ relation at z~0.55, revealing a steep slope and minimal scatter, consistent with passive evolution and the core elliptical galaxy population.

Contribution

It introduces a novel hierarchical Bayesian method to deconvolve observational errors and accurately characterize the L-$\sigma$ relation at high redshift.

Findings

Steep slope of $eta=7.8 \\pm 1.1$ in the L-$\\sigma$ relation.

Very small intrinsic scatter of 0.047 in log$_{10} \\sigma$.

No significant evolution of the relation from z~0.55 to z~0.1.

Abstract

We measure the intrinsic relation between velocity dispersion ($\sigma$) and luminosity ($L$) for massive, luminous red galaxies (LRGs) at redshift $z \sim 0.55$. We achieve unprecedented precision by using a sample of 600,000 galaxies with spectra from the Baryon Oscillation Spectroscopic Survey (BOSS) of the third Sloan Digital Sky Survey (SDSS-III), covering a range of stellar masses $M_* \gtrsim 10^{11} M_{\odot}$. We deconvolve the effects of photometric errors, limited spectroscopic signal-to-noise ratio, and red--blue galaxy confusion using a novel hierarchical Bayesian formalism that is generally applicable to any combination of photometric and spectroscopic observables. For an L-$\sigma$ relation of the form $L \propto \sigma^{\beta}$, we find $\beta = 7.8 \pm 1.1$ for $\sigma$ corrected to the effective radius, and a very small intrinsic scatter of $s = 0.047 \pm 0.004$ in $\log_{10} \sigma$ at fixed $L$. No significant redshift evolution is found for these parameters. The evolution of the zero-point within the redshift range considered is consistent with the passive evolution of a galaxy population that formed at redshift $z=2-3$, assuming single stellar populations. An analysis of previously reported results seems to indicate that the passively-evolved high-mass L-$\sigma$ relation at $z\sim0.55$ is consistent with the one measured at $z=0.1$. Our results, in combination with those presented in Montero-Dorta et al. (2014), provide a detailed description of the high-mass end of the red sequence (RS) at $z\sim0.55$. This characterization, in the light of previous literature, suggest that the high-mass RS distribution corresponds to the "core" elliptical population.