THE 4 Ms CHANDRA DEEP FIELD-SOUTH NUMBER COUNTS APPORTIONED BY SOURCE CLASS: PERVASIVE ACTIVE GALACTIC NUCLEI AND THE ASCENT OF NORMAL GALAXIES

By B. Lehmer, Y. Xue, W. N. Brandt, D. Alexander, F. Bauer, M. Brusa, A. Comastri, R. Gilli, A. Hornschemeier, B. Luo and 6 more. 2012

158 citations recorded by the source corpus.

We present 0.5–2 keV, 2–8 keV, 4–8 keV, and 0.5–8 keV (hereafter soft, hard, ultra-hard, and full bands, respectively) cumulative and differential number-count (log N–log S) measurements for the recently completed ≈4 Ms Chandra Deep Field-South (CDF-S) survey, the deepest X-ray survey to date. We implement a new Bayesian approach, which allows reliable calculation of number counts down to flux limits that are factors of ≈1.9–4.3 times fainter than the previously deepest number-count investigations. In the soft band (SB), the most sensitive bandpass in our analysis, the ≈4 Ms CDF-S reaches a maximum source density of ≈27,800 deg−2. By virtue of the exquisite X-ray and multiwavelength data available in the CDF-S, we are able to measure the number counts from a variety of source populations (active galactic nuclei (AGNs), normal galaxies, and Galactic stars) and subpopulations (as a function of redshift, AGN absorption, luminosity, and galaxy morphology) and test models that describe their evolution. We find that AGNs still dominate the X-ray number counts down to the faintest flux levels for all bands and reach a limiting SB source density of ≈14,900 deg−2, the highest reliable AGN source density measured at any wavelength. We find that the normal-galaxy counts rise rapidly near the flux limits and, at the limiting SB flux, reach source densities of ≈12,700 deg−2 and make up 46% ± 5% of the total number counts. The rapid rise of the galaxy counts toward faint fluxes, as well as significant normal-galaxy contributions to the overall number counts, indicates that normal galaxies will overtake AGNs just below the ≈4 Ms SB flux limit and will provide a numerically significant new X-ray source population in future surveys that reach below the ≈4 Ms sensitivity limit. We show that a future ≈10 Ms CDF-S would allow for a significant increase in X-ray-detected sources, with many of the new sources being cosmologically distant (z ≳ 0.6) normal galaxies.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/7d4f1063f6a0da3179289f4a4ebdf221d9642383

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Nuclear and High Energy Physics

Citations in the corpus

Charting the parameter space of the global 21-cm signal (2016, background): “The photons that produce early cosmic heating might also contribute to the unresolved soft X-ray background observed by c© 2016 RAS, MNRAS 000, 1–16 Chandra (Lehmer et al. 2012) which can be used to put upper limits on the efficiency of X-ray sources (Fialkov et al. 2016).”
THE 2 Ms CHANDRA DEEP FIELD-NORTH SURVEY AND THE 250 Ks EXTENDED CHANDRA DEEP FIELD-SOUTH SURVEY: IMPROVED POINT-SOURCE CATALOGS (2016, background): “The vast majority of both the new and old galaxies are located within the GOODS-N area that has the deepest exposures (see Figure 3), as a result of their growing numbers at the faintest fluxes (e.g., Bauer et al. 2004; Lehmer et al. 2012).”
Radiation Backgrounds at Cosmic Dawn: X-Rays from Compact Binaries (2016, methodology): “…(see Table 4 in Lehmer et al. 2016), µj and σj for j = 17,18 are the total observed unresolved X-ray background plus resolved normal-galaxy emission in the soft and hard bands, as reported by Lehmer et al. (2012), and Mi,j are the predictions of the ith model for each of these quantities.”
TOWARD THE STANDARD POPULATION SYNTHESIS MODEL OF THE X-RAY BACKGROUND: EVOLUTION OF X-RAY LUMINOSITY AND ABSORPTION FUNCTIONS OF ACTIVE GALACTIC NUCLEI INCLUDING COMPTON-THICK POPULATIONS (2014, methodology): “We also check the AGN source counts in the 2–8 keV band at a representative flux ofS = 2.7× 10−16 erg cm−2 s−1, which sensitively depends on the assumedfCTK parameter, to be compared with theChandraresult obtained by Lehmer et al. (2012),N(> S= 2.7× 10−16) = 4290± 240 deg−2 (for AGN only).”
THE SDSS-III BARYON OSCILLATION SPECTROSCOPIC SURVEY: THE QUASAR LUMINOSITY FUNCTION FROM DATA RELEASE NINE (2012, background): “We leave investigations of the obscured AGN population to other studies, e.g., in the mid-infrared (e.g., Lacy et al. 2004; Richards et al. 2006a; Stern et al. 2012; Yan et al. 2012), and X-ray (Tueller et al. 2010; Luo et al. 2011; Corral et al. 2011; Brightman & Ueda 2012; Lehmer et al. 2012).”
Cosmic X-ray surveys of distant active galaxies (2015, methodology): “6; Lehmer et al 2012), making them ≈ 500 times more numerous on the sky than SDSS quasars.”
X-RAY BINARY EVOLUTION ACROSS COSMIC TIME (2012, background): “…been established and appear to hold to at leastz = 1 (e.g. Bauer et al. 2002; Lehmer et al. 2008; Vattakunnel et al. 2012; Symeonidis et al. 2011; Lehmer et al. 2012), implying a large-scale regularity to the production of X-ray binaries (XRBs) and hot gas, the primary sources of high energy…”
THE CHANDRA COSMOS LEGACY SURVEY: OPTICAL/IR IDENTIFICATIONS (2015, background): “X-ray data play an important role in the selection of AGN, because at these energies the contamination from non-nuclear emission, mainly due to star-formation processes, is far less significant than in optical and infrared surveys (Donley et al. 2008, 2012; Stern et al. 2012; Lehmer et al. 2012).”
THE CHANDRA COSMOS SURVEY. III. OPTICAL AND INFRARED IDENTIFICATION OF X-RAY POINT SOURCES (2012, background): “…advantage of ultra-deep surveys is that they are able to detect the X-ray emission of non-active galaxies at medium-high redshifts (Luo et al. 2011, Lehmer et al. 2012), although they do not probe a large cosmological volume and thus contain relatively small numbers of sources at any given…”
Active galactic nuclei: what’s in a name? (2017, background): “On the basis of these advantages, the deepest blank-field cosmic X-ray surveys have identified the largest reliable AGN source density to date (≈24 000 deg−2; Lehmer et al. 2012; Luo et al. 2017 and Sect.”
THE CHANDRA COSMOS LEGACY SURVEY: OVERVIEW AND POINT SOURCE CATALOG (2016, background): “In the same Figure we compare our data with the 4 Ms CDFS (Xue et al. 2011) and the large area Stripe82 survey (LaMassa et al. 2013a,b) source flux distributions, respectively to the left and to the right of COSMOSLegacy flux distribution.”