We present a comparison of the observed , spatially integrated stellar and ionized gas velocity dispersions of \sim 1000 massive ( \log M _ { \star } / M _ { \odot } \gtrsim 10.3 ) galaxies in the Large Early Galaxy Astrophysics Census ( LEGA-C ) survey at 0.6 \lesssim z \lesssim 1.0 .
The high S / N \sim 20 { \AA ^ { -1 } } afforded by 20 hour VLT/VIMOS 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 ^ { \prime } _ { g,int } and \sigma ^ { \prime } _ { \star,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 \langle \log ( \sigma ^ { \prime } _ { g,int } / \sigma ^ { \prime } _ { \star,int } ) \rangle = -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 ^ { \prime } _ { g,int } and \sigma ^ { \prime } _ { \star,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 ^ { \prime } _ { g,int } and \sigma ^ { \prime } _ { \star,int } translates to an additional uncertainty of \sim 0.24 dex on dynamical mass derived from \sigma ^ { \prime } _ { g,int } , on top of measurement errors and uncertainties from Virial constant or size estimates .
We measure the z \sim 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 .