The Sloan Digital Sky Survey Reverberation Mapping Project: The Black Hole Mass-Stellar Mass Relations at 0.2 ≲ z ≲ 0.8

We measure the correlation between black hole mass M-BH and host stellar mass M-* for a sample of 38 broad-line quasars at 0.2 less than or similar to z less than or similar to 0.8 (median redshift z(med) = 0.5). The black hole masses are derived from a dedicated reverberation mapping program for distant quasars, and the stellar masses are derived from two-band optical+IR Hubble Space Telescope imaging. Most of these quasars are well centered within less than or similar to 1 kpc from the host galaxy centroid, with only a few cases in merging/disturbed systems showing larger spatial offsets. Our sample spans two orders of magnitude in stellar mass (10(9)-10(11) M-circle dot) and black hole mass (10(7)-10(9) M-circle dot) and reveals a significant correlation between the two quantities. We find a best-fit intrinsic (i.e., selection effects corrected) M-BH-M-*,M-host relation of log(M-BH/M-circle dot) = 7.01(-0.33)(+0.23) + 1.74(-0.64)(+0.64) log(M-*,M-host/10(10)M(circle dot)), with an intrinsic scatter of 0.47(-0.17)(+0.24) dex. Decomposing our quasar hosts into bulges and disks, there is a similar M-BH-M-*,M-bulge relation with slightly larger scatter, likely caused by systematic uncertainties in the bulge-disk decomposition. The M-BH-M-*,M-host relation at z(med) = 0.5 is similar to that in local quiescent galaxies, with negligible evolution over the redshift range probed by our sample. With direct black hole masses from reverberation mapping and the large dynamical range of the sample, selection biases do not appear to affect our conclusions significantly. Our results, along with other samples in the literature, suggest that the locally measured black hole mass-host stellar mass relation is already in place at z similar to 1.