A Serendipitous XMM Survey of the SDSS: the evolution of the colour-magnitude diagram of X-ray AGN from z=0.8 to z=0.1

TL;DR

This study uses a new XMM/SDSS survey to analyze the evolution of X-ray AGN host galaxy colours from redshift 0.8 to 0.1, finding no significant change in their rest-frame colours over this period.

Contribution

It introduces a new serendipitous XMM survey with improved sensitivity and source detection methods, and applies it to study AGN host galaxy evolution across cosmic time.

Findings

No evidence for evolution in the colours of X-ray AGN hosts from z=0.8 to z=0.1.

Suggests the dominant AGN accretion mode remains unchanged over this redshift range.

Challenges scenarios attributing the decline in cosmic accretion power to changes in fueling modes.

Abstract

A new serendipitous XMM survey in the area of the Sloan Digital Sky Survey is described (XMM/SDSS), which includes features such as the merging of overlapping fields to increase the sensitivity to faint sources, the use of a new parametrisation of the XMM point spread function for the source detection and photometry, the accurate estimation of the survey sensitivity. About 40,000 X-ray point sources are detected over a total area of 122deg2. A subsample of 209 sources detected in the 2-8keV spectral band with SDSS spectroscopic redshifts in the range 0.03<z<0.2, optical magnitudes r<17.77mag and logLx(2-10keV)>41.5 (erg/s) are selected to explore their distribution on the colour magnitude diagram. This is compared with the colour-magnitude diagram of X-ray AGN in the AEGIS field at z~0.8. We find no evidence for evolution of the rest-frame colours of X-ray AGN hosts from z=0.8 to z=0.1. This suggests that the dominant accretion mode of the AGN population, which is expected to imprint on the properties of their host galaxies, does not change since z=0.8. This argues against scenarios which attribute the rapid decline of the accretion power of the Universe with time (1dex since z=0.8) to changes in the AGN fueling/triggering mode.