Molecular Gas Kinematics and Star Formation Properties of the Strongly-lensed Quasar Host Galaxy RXS J1131–1231
- Department of Astronomy, Space Sciences Building, Cornell University, Ithaca, NY 14853 (United States)
We report observations of CO(J = 2 → 1) and CO(J=3→2) line emission toward 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{sub CO}∼6 kpc and a dynamical mass of M{sub dyn}∼8×10{sup 10} M {sub ⊙}. We also find a secondary CO-emitting source near RXS J1131−1231, the location of which is consistent with the optically-faint companion reported in previous studies. The lensing-corrected molecular gas masses are M {sub gas} = (1.4 ± 0.3) × 10{sup 10} M {sub ⊙} and (2.0 ± 0.1) × 10{sup 9} M {sub ⊙} for RXS J1131−1231 and the companion, respectively. We find a lensing-corrected stellar mass of M {sub *} = (3 ± 1) × 10{sup 10} M {sub ⊙} and a star formation rate of SFR{sub FIR} = (120 ± 63) M {sub ⊙} yr{sup −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 M{sub BH}/M{sub bulge} ratio of >0.27{sub −0.08}{sup +0.11}% 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.
- OSTI ID:
- 22869327
- Journal Information:
- Astrophysical Journal, Vol. 836, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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