1D Kinematics from Stars and Ionized Gas at z similar to 0.8 from the LEGA-C Spectroscopic Survey of Massive Galaxies

We present a comparison of the observed, spatially integrated stellar and ionized gas velocity dispersions of similar to 1000 massive (log M-*/M-circle dot greater than or similar to 10.3) galaxies in the Large Early Galaxy Astrophysics Census survey at 0.6 less than or similar to z less than or similar to 1.0. The high S/N similar to 20 angstrom(-1) afforded by 20 hr Very Large Telescope/Visible Multi-Object Spectrograph spectra allows for joint modeling of the stellar continuum and emission lines in all galaxies, spanning the full range of galaxy colors and morphologies. These observed integrated velocity dispersions (denoted as sigma '(g,int) and sigma '(*,int)) are related to the intrinsic velocity dispersions of ionized gas or stars, but also include rotational motions through beam smearing and spectral extraction. We find good average agreement between observed velocity dispersions, with a (log(sigma '(g,int)/sigma '(*,int))) n = -0.003. This result does not depend strongly on stellar population, structural properties, or alignment with respect to the slit. However, in all regimes we find significant scatter between sigma '(g,int) and sigma '(*,int),with an overall scatter of 0.13 dex of which 0.05 dex is due to observational uncertainties. For an individual galaxy, the scatter between sigma '(g,int) and sigma '(*,int) translates to an additional uncertainty of similar to 0.24 dex on dynamical mass derived from sigma '(g,int), on top of measurement errors and uncertainties from Virial constant or size estimates. We measure the z similar to 0.8 stellar mass Faber-Jackson relation and demonstrate that emission line widths can be used to measure scaling relations. However, these relations will exhibit increased scatter and slopes that are artificially steepened by selecting on subsets of galaxies with progressively brighter emission lines.