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

Abstract

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 Almost-Equal-To 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 Almost-Equal-To 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 Almost-Equal-To 4 Ms CDF-S reaches a maximum source density of Almost-Equal-To 27,800 deg{sup -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 Almost-Equal-To 14,900 deg{sup -2}, the highest reliable AGN source density measured at any wavelength.more » We find that the normal-galaxy counts rise rapidly near the flux limits and, at the limiting SB flux, reach source densities of Almost-Equal-To 12,700 deg{sup -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 Almost-Equal-To 4 Ms SB flux limit and will provide a numerically significant new X-ray source population in future surveys that reach below the Almost-Equal-To 4 Ms sensitivity limit. We show that a future Almost-Equal-To 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 {approx}> 0.6) normal galaxies.« less

Authors:
 [1]; ; ;  [2];  [3];  [4];  [5]; ;  [6]; ;  [7];  [8];  [9];  [10];  [11];  [12]
  1. Johns Hopkins University, Homewood Campus, Baltimore, MD 21218 (United States)
  2. Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States)
  3. Department of Physics, Durham University, Durham DH1 3LE (United Kingdom)
  4. Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile)
  5. Max-Planck-Institut fuer Extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany)
  6. INAF-Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna (Italy)
  7. NASA Goddard Space Flight Centre, Code 662, Greenbelt, MD 20771 (United States)
  8. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
  9. Dipartimento di Scienze Fisiche, Universita Federico II di Napoli, Via Cinthia, I-80126 Napoli (Italy)
  10. Department of Physics, University of North Texas, Denton, TX 76203 (United States)
  11. INAF-Osservatorio Astronomico di Trieste, Via Tiepolo 11, I-34131 Trieste (Italy)
  12. Dipartimento di Astronomia, Universita di Bologna, Via Ranzani 1, I-40127 Bologna (Italy)
Publication Date:
OSTI Identifier:
22037081
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 752; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; ASTRONOMY; ASTROPHYSICS; COSMOLOGY; DENSITY; GALACTIC EVOLUTION; GALAXY NUCLEI; KEV RANGE; LUMINOSITY; MORPHOLOGY; RED SHIFT; SENSITIVITY; STARS; X RADIATION; X-RAY GALAXIES

Citation Formats

Lehmer, B. D., Xue, Y. Q., Brandt, W. N., Schneider, D. P., Alexander, D. M., Bauer, F. E., Brusa, M., Comastri, A., Gilli, R., Hornschemeier, A. E., Ptak, A., Luo, B., Paolillo, M., Shemmer, O., Tozzi, P., and Vignali, C. THE 4 Ms CHANDRA DEEP FIELD-SOUTH NUMBER COUNTS APPORTIONED BY SOURCE CLASS: PERVASIVE ACTIVE GALACTIC NUCLEI AND THE ASCENT OF NORMAL GALAXIES. United States: N. p., 2012. Web. doi:10.1088/0004-637X/752/1/46.
Lehmer, B. D., Xue, Y. Q., Brandt, W. N., Schneider, D. P., Alexander, D. M., Bauer, F. E., Brusa, M., Comastri, A., Gilli, R., Hornschemeier, A. E., Ptak, A., Luo, B., Paolillo, M., Shemmer, O., Tozzi, P., & Vignali, C. THE 4 Ms CHANDRA DEEP FIELD-SOUTH NUMBER COUNTS APPORTIONED BY SOURCE CLASS: PERVASIVE ACTIVE GALACTIC NUCLEI AND THE ASCENT OF NORMAL GALAXIES. United States. doi:10.1088/0004-637X/752/1/46.
Lehmer, B. D., Xue, Y. Q., Brandt, W. N., Schneider, D. P., Alexander, D. M., Bauer, F. E., Brusa, M., Comastri, A., Gilli, R., Hornschemeier, A. E., Ptak, A., Luo, B., Paolillo, M., Shemmer, O., Tozzi, P., and Vignali, C. Sun . "THE 4 Ms CHANDRA DEEP FIELD-SOUTH NUMBER COUNTS APPORTIONED BY SOURCE CLASS: PERVASIVE ACTIVE GALACTIC NUCLEI AND THE ASCENT OF NORMAL GALAXIES". United States. doi:10.1088/0004-637X/752/1/46.
@article{osti_22037081,
title = {THE 4 Ms CHANDRA DEEP FIELD-SOUTH NUMBER COUNTS APPORTIONED BY SOURCE CLASS: PERVASIVE ACTIVE GALACTIC NUCLEI AND THE ASCENT OF NORMAL GALAXIES},
author = {Lehmer, B. D. and Xue, Y. Q. and Brandt, W. N. and Schneider, D. P. and Alexander, D. M. and Bauer, F. E. and Brusa, M. and Comastri, A. and Gilli, R. and Hornschemeier, A. E. and Ptak, A. and Luo, B. and Paolillo, M. and Shemmer, O. and Tozzi, P. and Vignali, C.},
abstractNote = {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 Almost-Equal-To 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 Almost-Equal-To 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 Almost-Equal-To 4 Ms CDF-S reaches a maximum source density of Almost-Equal-To 27,800 deg{sup -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 Almost-Equal-To 14,900 deg{sup -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 Almost-Equal-To 12,700 deg{sup -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 Almost-Equal-To 4 Ms SB flux limit and will provide a numerically significant new X-ray source population in future surveys that reach below the Almost-Equal-To 4 Ms sensitivity limit. We show that a future Almost-Equal-To 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 {approx}> 0.6) normal galaxies.},
doi = {10.1088/0004-637X/752/1/46},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 752,
place = {United States},
year = {2012},
month = {6}
}