Cross-Correlation of the 2-10 keV X-Ray Background with Radio Sources: Constraining the Large-Scale Structure of the X-Ray Background
Abstract
We present cross-correlation analyses of the HEAO 2-10 keV diffuse X-ray map with both the combined GB6/Parkes-MIT-NRAO (GB6-PMN) 5 GHz and the FIRST 1.4 GHz radio surveys. The cross-correlation functions (CCFs) of both radio surveys with the unresolved X-ray background were detected at the 5 σ level. While the large angular resolution (3°) of the X-ray map makes it difficult to separate the contributions of clustering from those of Poisson fluctuations, the amplitude of the CCF provides important constraints on the X-ray emissivity of the radio sources, as well as on the clustering properties of radio and X-ray sources. These constraints are subject to a number of modeling parameters, e.g., X-ray luminosity evolution, clustering evolution, the radio luminosity function, cosmological model, etc. For reasonable choices of parameters the X-ray/FIRST CCF is consistent with a correlation scale length of 6 h-1 Mpc. This is somewhat smaller than the scale length inferred from the autocorrelation function of the FIRST survey and implies that X-ray sources are less strongly clustered than strong radio sources, a result that is consistent with previous constraints on X-ray clustering. The X-ray/GB6-PMN CCF is several times larger and is likely to be dominated by Poisson fluctuations. This implies that ~2% of the diffuse X-ray background arises from the GB6-PMN sources.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 1998
- DOI:
- 10.1086/305674
- arXiv:
- arXiv:astro-ph/9709077
- Bibcode:
- 1998ApJ...499..533B
- Keywords:
-
- Cosmology: Diffuse Radiation;
- Galaxies: Statistics;
- Cosmology: Large-Scale Structure of Universe;
- Radio Continuum: Galaxies;
- X-Rays: Galaxies;
- X-Rays: General;
- Astrophysics
- E-Print:
- 25 pages, with 8 figures included. Submitted to ApJ. sboughn@haverford.edu