http://arxiv.org/abs/1701.07830
We report observations of CO(J=2-1) and CO(J=3-2) line emission towards the quadruply-lensed quasar RXS J1131-1231 at z = 0.654 obtained using the Plateau de Bure Interferometer (PdBI) and the Combined Array for Research in Millimeter-wave Astronomy (CARMA). Our lens modeling shows that the asymmetry in the double-horned CO(J = 2-1) line profile is mainly a result of differential lensing, where the magnification factor varies from ~3 to ~9 across different kinematic components. The intrinsically symmetric line profile and a smooth source-plane velocity gradient suggest that the host galaxy is an extended rotating disk, with a CO size of R_CO~6 kpc and a dynamical mass of M_dyn~8×10^10 Msun. We also find a secondary CO-emitting source near RXS J1131-1231 whose location is consistent with the optically-faint companion reported in previous studies. The lensing-corrected molecular gas masses are M_gas = (1.4+/-0.3)x10^10 Msun and (2.0+/-0.1)x10^9 Msun for RXS J1131-1231 and the companion, respectively. We find a lensing-corrected stellar mass of M_* = (3+/-1)x10^10 Msun and a star formation rate of SFR_FIR = (120+/-63) Msun yr^-1 , corresponding to a specific SFR and star formation efficiency comparable to z~1 disk galaxies not hosting quasars. The implied gas mass fraction of ~18+/-4% is consistent with the previously-observed cosmic decline since z~2. We thus find no evidence for quenching of star formation in RXS J1131-1231. This agrees with our finding of an elevated MBH/Mbulge ratio of >0.27+0.11% -0.08 compared to the local value, suggesting that the bulk of its black hole mass is largely in place while its stellar bulge is still assembling.
T. Leung, D. Riechers and R. Pavesi
Mon, 30 Jan 2017
16/41
Comments: 19 pages, 10 figures, 6 tables, to be appear in the ApJ