Gravitational lensing reveals extreme dust-obscured star formation in quasar host galaxies
Abstract
We have observed 104 gravitationally lensed quasars at z ∼ 1-4 with Herschel/SPIRE, the largest such sample ever studied. By targeting gravitational lenses, we probe intrinsic far-infrared (FIR) luminosities and star formation rates (SFRs) more typical of the population than the extremely luminous sources that are otherwise accessible. We detect 72 objects with Herschel/SPIRE and find 66 per cent (69 sources) of the sample have spectral energy distributions (SEDs) characteristic of dust emission. For 53 objects with sufficiently constrained SEDs, we find a median effective dust temperature of 38^{+12}_{-5} K. By applying the radio-infrared correlation, we find no evidence for an FIR excess that is consistent with star-formation-heated dust. We derive a median magnification-corrected FIR luminosity of 3.6^{+4.8}_{-2.4} × 10^{11} L_{⊙} and median SFR of 120^{+160}_{-80} M_{⊙} yr^{-1}} for 94 quasars with redshifts. We find ∼10 per cent of our sample have FIR properties similar to typical dusty star-forming galaxies at z ∼ 2-3 and a range of SFRs <20-10 000 M⊙ yr-1 for our sample as a whole. These results are in line with current models of quasar evolution and suggests a coexistence of dust-obscured star formation and AGN activity is typical of most quasars. We do not find a statistically significant difference in the FIR luminosities of quasars in our sample with a radio excess relative to the radio-infrared correlation. Synchrotron emission is found to dominate at FIR wavelengths for <15 per cent of those sources classified as powerful radio galaxies.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- June 2018
- DOI:
- 10.1093/mnras/sty458
- arXiv:
- arXiv:1705.10530
- Bibcode:
- 2018MNRAS.476.5075S
- Keywords:
-
- gravitational lensing: strong;
- galaxies: evolution;
- quasars: general;
- galaxies: star formation;
- infrared: galaxies;
- submillimetre: galaxies;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 47 pages, 89 figures, accepted for publication in MNRAS