Charity Woodrum, Inger Jorgensen, Scott Fisher, Lindsey Oberhelman, and Taylor Contreras. 8/20/2017. “
The Evolution of Bulge-Dominated Field Galaxies from z~1 to the Present.” The Astrophysical Journal, 847, 1.
Publisher's VersionAbstractWe analyze the stellar populations and evolutionary history of bulge-dominated field galaxies at redshifts

as part of the Gemini/
Hubble Space Telescope (
HST) Galaxy Cluster Project (GCP). High signal-to-noise optical spectroscopy from the Gemini Observatory and imaging from the
HST are used to analyze a total of 43 galaxies, focusing on the 30 passive galaxies in the sample. Using the size–mass and velocity dispersion–mass relations for the passive field galaxies we find no significant evolution of sizes or velocity dispersions at a given dynamical mass between

and the present. We establish the Fundamental Plane and study mass-to-light (
M/L) ratios. The
M/L versus dynamical mass relation shows that the passive field galaxies follow a relation with a steeper slope than the local comparison sample, consistent with cluster galaxies in the GCP at
z = 0.86. This steeper slope indicates that the formation redshift is mass dependent, in agreement with "downsizing," meaning that the low-mass galaxies formed their stars more recently while the high-mass galaxies formed theirs at higher redshift. The zero-point differences of the scaling relations for the
M/L ratios imply a formation redshift of

for the passive field galaxies. This is consistent with the

line index which implies a formation redshift of

.