The Resolved Fraction of the Cosmic X-Ray Background

By A.Moretti, S.Campana, D. Lazzati, G. I. Italy, UK IoACambridge. 2003

302 citations recorded by the source corpus.

We present the X-ray source number counts in two energy bands (0.5-2 and 2-10 keV) from a very large source sample: we combine data of six different surveys, both shallow wide-field and deep pencil-beam, performed with three different satellites (ROSAT, Chandra, and XMM-Newton). The sample covers with good statistics the largest possible flux range so far: 2.4 × 10-17 to 10-11 ergs s-1 cm-2 in the soft band and 2.1 × 10-16 to 8 × 10-12 ergs s-1 cm-2 in the hard band. Integrating the flux distributions over this range and taking into account the (small) contribution of the brightest sources, we derive the flux density generated by discrete sources in both bands. After a critical review of the literature values of the total cosmic X-ray background (CXB) we conclude that, with the present data, 94.3 % and 88.8 % of the soft and hard CXB can be ascribed to discrete source emission. If we extrapolate the analytical form of the log N-log S distribution beyond the flux limit of our catalog in the soft band we find that the flux from discrete sources at ~3 × 10-18 ergs s-1 cm-2 is consistent with the entire CXB, whereas in the hard band it accounts for only 93% of the total CXB at most, hinting at a faint and obscured population to arise at even fainter fluxes.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/2022098953d2ad7f988af763c036ad679d8f54a0

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In Astronomy and Astrophysics

1. D. M. Alexander
2. W. N. Brandt
3. G. Hasinger
4. P. Hopkins
5. A. Merloni
6. F. E. Bauer
7. L. Hernquist
8. R. Hickox

In Nuclear and High Energy Physics

1. D. M. Alexander
2. W. N. Brandt
3. G. Hasinger
4. A. Merloni
5. F. E. Bauer
6. T. Miyaji
7. S. Heinz
8. Alexey Boyarsky

Citations in the corpus

• THE 4 Ms CHANDRA DEEP FIELD-SOUTH NUMBER COUNTS APPORTIONED BY SOURCE CLASS: PERVASIVE ACTIVE GALACTIC NUCLEI AND THE ASCENT OF NORMAL GALAXIES (2012, background): “…Italy 13 Universitá di Bologna, Via Ranzani 1, Bologna, Italy of X-ray sources per unit area,N, increases with decreasing flux, S (also referred to as logN–logS; see, e.g., Brandt et al. 2001; Rosati et al. 2002; Moretti et al. 2003; Bauer et al. 2004; Kim et al. 2007; Georgakakis et al. 2008).”
• Constraints on sterile neutrinos as dark matter candidates from the diffuse X-ray background (2005, background): “The increased angular resolution and sensitivity of these instruments 3The normalization of the XRB spectrum, measured by HEAO-1, is known to be lower than any other XRB measurements (Gilli 2003; Moretti et al. 2003).”
• The Fall of Active Galactic Nuclei and the Rise of Star-forming Galaxies: A Close Look at the Chandra Deep Field X-Ray Number Counts (2004, background): “Deep Chandra and XMM-Newton observations have now resolved the vast majority of the X-ray background (XRB) below 8 keV (e.g., Cowie et al. 2002, hereafter C02; Moretti et al. 2003, hereafter M03; Worsley et al. 2004a), with much of the remaining uncertainty in the resolved fraction attributed to dev”
• Swift BAT Survey of AGNs (2007, methodology): “Using the Moretti et al. (2003) log NY log S distribution based on Chandra data there are 50 or 20 sources deg 2, respectively, at these levels.”
• The Chandra Deep Field North Survey. XIII. 2 Ms Point-Source Catalogs (2003, background): “These ultradeep Chandra surveys resolve the bulk of the 0.5– 8.0 keV background, providing the deepest views of the universe in this band (e.g., Campana et al. 2001; Cowie et al. 2002; Rosati et al. 2002; Moretti et al. 2003).”
• DEEP EXTRAGALACTIC X-RAY SURVEYS (2005, background): “At bright fluxes the integral counts have power-law slopes in the range αb ≈ 1.6 ± 0.2, depending on the sample selection (compare, e.g., the discussions about bright-end slopes in Hasinger et al. 1998 and Moretti et al. 2003).”
• The PalermoSwift-BAT hard X-ray catalogue: II. Results after 39 months of sky survey (2009, background): “…identify which class of sources gives the larger contribution: while the CXB at energies lower than 10 keV has been almost entirely resolved (80–90%, Moretti et al. 2003; Worsley et al. 2005, 2006; Brandt & Hasinger 2005), only a∼1.5% of the CXB at higher energies can be associated with resolved…”
• CONSTRAINING THE MILKY WAY'S HOT GAS HALO WITH O vii AND O viii EMISSION LINES (2014, background): “The latter accounts for sightline-to-sightline variation in the EPL normalization parameter due to variable soft proton contamination and/or unresolved sources with F 0.5−2.0X <5× 10 −14 erg cm−2 s−1 (Moretti et al. 2003).”
• The unresolved hard X-ray background: the missing source population implied by the Chandra and XMM-Newton deep fields (2004, methodology): “There is now some evidence to suggest that the Moretti et al. (2003) log N – log S slope is too steep at the bright end compared with results from the RIXOS,1 RBS2 and NEPS3 surveys (Mason et al. 2000; Schwope et al. 2000; Gioia et al. 2003); thus, our bright-end correction in the soft band could…”
• A synthesis model for AGN evolution: supermassive black holes growth and feedback modes (2008, background): “Indeed, this class of objects dominates the counts in the X-ray energy band where almost the entire XRB radiation has been resolved into individual sources (Hasinger et al. 1998; Rosati et al. 2002; Alexander et al. 2003; Moretti et al. 2003; Worsley et al. 2005).”
• Luminosity-dependent evolution of soft X-ray selected AGN : New Chandra and XMM-Newton surveys (2005, background): “Moretti et al. (2003), on the other hand, have derived a significantly steeper bright flux slope (αb ≈ 2.8) from ROSAT HRI pointed observations.”
• A COMPLETE SAMPLE OF ULTRALUMINOUS X-RAY SOURCE HOST GALAXIES (2011, methodology): “The number of potential background sources included in the search fields can be estimated from the published fits to the 2.0–10.0 keV cosmic X-ray background log N − log S distribution (Moretti et al. 2003) as follows.”
• Chandra and Spitzer Unveil Heavily Obscured Quasars in the Chandra/SWIRE Survey (2006, background): “More than 85% of the 2–10 keV cosmic X-ray background (CXRB) has been resolved by sources detected in deep X-ray surveys (Moretti et al. 2003; De Luca & Molendi 2004).”