Galaxy Structure, Stellar Populations, and Star Formation Quenching at 0.6 ≲ z ≲ 1.2

We use both photometric and spectroscopic data from the Hubble Space Telescope to explore the relationships among 4000 angstrom break (D4000) strength, colors, stellar masses, and morphology, in a sample of 352 galaxies with log(M-*/M-circle dot) > 9.44 at 0.6 less than or similar to z less than or similar to 1.2. We have identified authentically quiescent galaxies in the UVJ diagram based on their D4000 strengths. This spectroscopic identification is in good agreement with their photometrically derived specific star formation rates (sSFRs). Morphologically, most (that is, 66 out of 68 galaxies, similar to 97%) of these newly identified quiescent galaxies have a prominent bulge component. However, not all of the bulge-dominated galaxies are quenched. We found that bulge-dominated galaxies show positive correlations among the D4000 strength, stellar mass, and Sersic index, while late-type disks do not show such strong positive correlations. Also, bulge-dominated galaxies are clearly separated into two main groups in the parameter space of sSFR versus stellar mass and stellar surface density within the effective radius, Sigma(e), while late-type disks and irregulars only show high sSFR. This split is directly linked to the "blue cloud" and the "red sequence" populations and correlates with the associated central compactness indicated by Sigma(e). While star-forming massive late-type disks and irregulars (with D4000 < 1.5 and log(M-*/M-circle dot) greater than or similar to 10.5) span a stellar mass range comparable to bulge-dominated galaxies, most have systematically lower Sigma(e) less than or similar to 10(9) M-circle dot kpc(-2). This suggests that the presence of a bulge is a necessary but not sufficient requirement for quenching at intermediate redshifts.