The Velocity Dispersion Function for Massive Quiescent and Star-Forming Galaxies at 0.6 $<$ z $\leq$ 1.0

TL;DR

This study provides the first direct spectroscopic measurement of the stellar velocity dispersion function for massive quiescent and star-forming galaxies at redshifts 0.6 to 1.0, revealing stability over time and extending to low velocity dispersions.

Contribution

It is the first work to directly measure the VDF for star-forming galaxies at these redshifts and low velocity dispersions, using high-quality spectra from the LEGA-C survey.

Findings

VDF remains remarkably stable between redshifts 0.6 and 1.0.

First direct measurement of the VDF for star-forming galaxies at these epochs.

Results are consistent with the high-sigma tail from BOSS data.

Abstract

We present the first direct spectroscopic measurement of the stellar velocity dispersion function (VDF) for massive quiescent and star-forming galaxies at $0.6 < z \leq 1.0$. For this analysis we use individual measurements of stellar velocity dispersion from high-S/N spectra from the public Large Early Galaxy Astrophysics Census (LEGA-C) survey. We report a remarkable stability of the VDF for both quiescent and star-forming galaxies within this redshift range, though we note the presence of weak evolution in the number densities of star-forming galaxies. We compare both VDFs with previous direct and inferred measurements at local and intermediate redshifts, with the caveat that previous measurements of the VDF for star-forming galaxies are poorly constrained at all epochs. We emphasize that this work is the first to directly push to low-stellar velocity dispersion ($\sigma_\star > 100$ km s$^{-1}$) and extend to star-forming galaxies. We are largely consistent with the high-sigma tail measured from BOSS, and we find that the VDF remains constant from the median redshift of LEGA-C, $z\sim0.8$, to the present day.