Deepest X-ray and far-infrared surveys find evidence for AGN-host co-evolution
Abstract
Models of galaxy evolution assume some connection between the AGN and star formation activity in galaxies. We use the multi-wavelength information of the Chandra Deep Field South to assess this issue. We select the AGN from the 3-Ms XMM-Newton survey and measure their star-formation rates using data that probe rest-frame wavelengths long ward of 20 microns, predominantly from the deep 100-micron and 160-micron GOODS-Herschel survey, but also from the MIPS 70-micron survey. Star-formation rates are obtained from spectral energy distribution fits, identifying and subtracting an AGN component. We divide the star-formation rates by the stellar masses of the hosts to derive specific star-formation rates (sSFR) and find evidence for a positive correlation between the AGN activity (proxied by the X-ray luminosity) and the sSFR for the most active systems with X-ray luminosities exceeding Lx=10^43 erg/s and redshifts z>1. We do not find evidence for such a correlation for lower luminosity systems or at lower redshifts, consistent with previous studies. We also do not find any correlation between the sSFR and the X-ray absorption derived from high-quality XMM-Newton spectra, showing that the absorption is likely to be linked to the nuclear region rather than the host, while the star-formation is not nuclear. Comparing the sSFR of the hosts to the characteristic sSFR of star-forming galaxies at the same redshift (the so-called "main sequence") we find that the AGN reside mostly in main-sequence and starburst hosts, reflecting the AGN - star-formation connection. Limiting our analysis to the highest X-ray luminosity AGN (X-ray QSOs with Lx>10^44 erg/s, we find that they reside predominantly in starburst hosts, with an average sSFR more than double that of the "main sequence".
- Publication:
-
Half a Century of X-ray Astronomy
- Pub Date:
- September 2012
- Bibcode:
- 2012hcxa.confE..50R