2008/04/04 by J. Aird, James Aird, Kirpal Nandra +9 · 1 citation
Physics and Astronomy · #Active galactic nucleus #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy formation and evolution #Luminosity #Luminosity function #Redshift #Selection (genetic algorithm) #astro-ph
paper · pdf · doi:10.1111/j.1365-2966.2008.13286.x
16 pages, 9 figures, accepted for publication in MNRAS
arxiv created 2008/04/04 · openalex publication_date 2008/05/13 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We combine Lyman-break colour selection with ultradeep (≳200 ks) Chandra X-ray imaging over a survey area of ∼0.35 deg2 to select high-redshift active galactic nuclei (AGN). Applying careful corrections for both the optical and X-ray selection functions, the data allow us to make the most accurate determination to date of the faint end of the X-ray luminosity function (XLF) at z∼ 3. Our methodology recovers a number density of X-ray sources at this redshift which is at least as high as previous surveys, demonstrating that it is an effective way of selecting high z AGN. Comparing to results at z= 1, we find no evidence that the faint slope of the XLF flattens at high z, but we do find significant (factor ∼3.6) negative evolution of the space density of low luminosity AGN. Combining with bright end data from very wide surveys we also see marginal evidence for continued positive evolution of the characteristic break luminosity L*. Our data therefore support models of luminosity-dependent density evolution between z= 1 and z= 3. A sharp upturn in the the XLF is seen at the very lowest luminosities (LX≲ 1042.5erg s−1), most likely due to the contribution of pure X-ray starburst galaxies at very faint fluxes.