2006MNRAS.366..171G -
Mon. Not. R. Astron. Soc., 366, 171-181 (2006/February-2)
Red active galactic nuclei in XMM-Newton/Sloan Digital Sky Survey fields.
GEORGAKAKIS A.E., GEORGANTOPOULOS I. and AKYLAS A.
Abstract (from CDS):
In this paper we combine archival and proprietary XMM-Newton observations (about 5deg2) that overlap with the Sloan Digital Sky Survey to explore the nature of the moderate-z X-ray population. We focus on X-ray sources with optically red colours (g - r > 0.4), which we argue are important for understanding the origin of the X-ray background (XRB). First, these systems constitute a significant fraction, about two-third, of the z ≲ 1 X-ray population to the limit f(2-8keV) ~ 2x10–14erg/s/cm2. Secondly, their luminosity function under evolution of the form ∝ (1 + z)3 suggests that they could be responsible for about 17 per cent of the diffuse XRB to z = 1. Thirdly, their stacked X-ray spectrum in the range 1-8keV is consistent with a power-law distribution with Γ ~ 1.4 (without fitting intrinsic absorption), that is, similar to the diffuse XRB. We find that the optically red X-ray population comprises a mixed bag of objects, both obscured [hydrogen column density (NH) > 1022/cm2] and unobscured (NH< 1022/cm2), with a wide range of X-ray luminosities up to LX~ 1044erg/s. We argue that dilution of the active galactic nucleus (AGN) light by the host galaxy may play a role in shaping the continuum optical emission of this population. Finally, we explore a possible association of these sources and the moderate-z red (J - Ks> 2mag) AGNs identified in the Two-Micron All-Sky Survey (2MASS). The median NHof the red X-ray sources studied here is ~1021/cm2, lower than that found for the 2MASS AGNs, suggesting different populations.
Abstract Copyright:
2005 The Authors. Journal compilation © 2005 RAS
Journal keyword(s):
surveys - X-rays: galaxies - X-rays: general
VizieR on-line data:
<Available at CDS (J/MNRAS/366/171): table1.dat>
Nomenclature:
Table 1: [GGA2006] NN (Nos 1-84).
Status at CDS
:
All or part of tables of objects could be ingested in SIMBAD with priority 2.
Simbad objects:
2
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