Higher prevalence of X-ray selected AGN in intermediate age galaxies up to z~1

Abstract

We analyse the stellar populations in the host galaxies of 53 X-ray selected optically dull active galactic nuclei (AGN) at 0.34<z<1.07 with ultra-deep (m=26.5) optical medium-band (R~50) photometry from the Survey for High-z Absorption Red and Dead Sources (SHARDS). The spectral resolution of SHARDS allows us to consistently measure the strength of the 4000 AA break, Dn(4000), a reliable age indicator for stellar populations. We confirm that most X-ray selected moderate-luminosity AGN (L_X<10^44 erg/s) are hosted by massive galaxies (typically M*>10^10.5 M_sun) and that the observed fraction of galaxies hosting an AGN increases with the stellar mass. A careful selection of random control samples of inactive galaxies allows us to remove the stellar mass and redshift dependencies of the AGN fraction to explore trends with several stellar age indicators. We find no significant differences in the distribution of the rest-frame U-V colour for AGN hosts and inactive galaxies, in agreement with previous results. However, we find significantly shallower 4000 AA breaks in AGN hosts, indicative of younger stellar populations. With the help of a model-independent determination of the extinction, we obtain extinction-corrected U-V colours and light-weighted average stellar ages. We find that AGN hosts have younger stellar populations and higher extinction compared to inactive galaxies with the same stellar mass and at the same redshift. We find a highly significant excess of AGN hosts with Dn(4000)~1.4 and light weighted average stellar ages of 300-500 Myr, as well as a deficit of AGN in intrinsic red galaxies. We interpret failure in recognising these trends in previous studies as a consequence of the balancing effect in observed colours of the age-extinction degeneracy.

Accepted for publication in MNRAS, 12 pages, 8 figures, 1 table

References in corpus (20)

• Star Formation in AEGIS Field Galaxies since z=1.1 : The Dominance of Gradually Declining Star Formation, and the Main Sequence of Star-Forming Galaxies
• UV Star Formation Rates in the Local Universe
• Detection of quiescent galaxies in a bicolor sequence from z=0-2
• The stellar mass assembly of galaxies from z=0 to z=4. Analysis of a sample selected in the rest-frame near-infrared with Spitzer
• A Close Look at Star Formation around Active Galactic Nuclei
• The bulk of the black hole growth since z~1 occurs in a secular universe: No major merger-AGN connection
• A synthesis model for AGN evolution: supermassive black holes growth and feedback modes
• The stellar masses of 25000 galaxies at 0.2<z<1.0 estimated by the COMBO-17 survey
• The Mean Star Formation Rate of X-ray selected Active Galaxies and its Evolution from z=2.5: Results from PEP-Herschel
• The Luminosity Function of X-ray Selected Active Galactic Nuclei: Evolution of Supermassive Black Holes at High Redshift
• AEGIS: The color-magnitude relation for X-ray selected AGN
• HST WFC3/IR Observations of Active Galactic Nucleus Host Galaxies at z~2: Supermassive Black Holes Grow in Disk Galaxies
• The XMM-Newton wide-field survey in the COSMOS field: III. optical identification and multiwavelength properties of a large sample of X-ray selected sources
• The VVDS type-1 AGN sample: The faint end of the luminosity function
• AEGIS: New Evidence Linking Active Galactic Nuclei to the Quenching of Star Formation
• Aromatic Features in AGN: Star-Forming Infrared Luminosity Function of AGN Host Galaxies
• The role of AGN in the colour transformation of galaxies at redshifts z~1
• Dust-Corrected Colors Reveal Bimodality in AGN Host Galaxy Colors at z~1
• The Host Galaxies and Black Holes of Typical z~0.5-1.4 AGN
• The OPTX Project I: The Flux and Redshift Catalogs for the CLANS, CLASXS, and CDF-N fields

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• The Chandra Deep Fields: Lifting the Veil on Distant Active Galactic Nuclei and X-Ray Emitting Galaxies
• The Incidence of X-ray selected AGN in Nearby Galaxies
• AGN and their host galaxies in the local Universe: two mass independent Eddington ratio distribution functions characterize black hole growth
• Comparing the host galaxy ages of X-ray selected AGN in COSMOS: Obscured AGN are associated with older galaxies
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