Photometric redshift of X-ray sources in the Chandra Deep Field-South

W. Zheng, V. J. Mikles, V. Mainieri, G. Hasinger, P. Rosati, C. Wolf, C. Norman, G. Szokoly, R. Gilli, P. Tozzi, J. X. Wang, A. Zirm, R. Giacconi

Research output: Contribution to journalArticle

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Abstract

Based on the photometry of 10 near-ultraviolet, optical, and near-infrared bands of the Chandra Deep Field-South, we estimate the photometric redshifts for 342 X-ray sources, which constitute ∼99% of all the detected X-ray sources in the field. The models of spectral energy distribution are based on galaxies and a combination of power-law continuum and emission lines. Color information is useful for source classifications: type I active galactic nuclei (AGNs) show nonthermal spectral features that are distinct from galaxies and type II AGNs. The hardness ratio in X-ray and the X-ray-to-optical flux ratio are also useful discriminators. Using rudimentary color separation techniques, we are able to further refine our photometric redshift estimations. Among these sources, 173 have reliable spectroscopic redshifts, which we use to verify the accuracy of photometric redshifts and to modify the model inputs. The average relative dispersion in redshift distribution is ∼8%, among the most accurate for photometric surveys. The high reliability of our results is attributable to the high quality and broad coverage of data as well as the applications of several independent methods and a careful evaluation of every source. We apply our redshift estimations to study the effect of redshift on broadband colors and to study the redshift distribution of AGNs. Our results show that both the hardness ratio and U - K color decline with redshift, which may be the result of a K-correction. The number of type II AGNs declines significantly at z > 2 and that of galaxies declines at z > 1. However, the distribution of type I AGNs exhibits less redshift dependence. As well, we observe a significant peak in the redshift distribution at z = 0.6. We demonstrate that our photometric redshift estimation produces a reliable database for the study of X-ray luminosity of galaxies and AGNs.

Original languageEnglish
Pages (from-to)73-87
Number of pages15
JournalAstrophysical Journal, Supplement Series
Volume155
Issue number1
DOIs
Publication statusPublished - Nov 2004

Fingerprint

active galactic nuclei
galaxies
color
x rays
hardness
discriminators
spectral energy distribution
near infrared
power law
photometry
distribution
luminosity
continuums
broadband
evaluation
energy
estimates

Keywords

  • Galaxies: active
  • Galaxies: distances and redshifts
  • Galaxies: photometry
  • X-rays: galaxies
  • X-rays: general

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Zheng, W., Mikles, V. J., Mainieri, V., Hasinger, G., Rosati, P., Wolf, C., ... Giacconi, R. (2004). Photometric redshift of X-ray sources in the Chandra Deep Field-South. Astrophysical Journal, Supplement Series, 155(1), 73-87. https://doi.org/10.1086/424385

Photometric redshift of X-ray sources in the Chandra Deep Field-South. / Zheng, W.; Mikles, V. J.; Mainieri, V.; Hasinger, G.; Rosati, P.; Wolf, C.; Norman, C.; Szokoly, G.; Gilli, R.; Tozzi, P.; Wang, J. X.; Zirm, A.; Giacconi, R.

In: Astrophysical Journal, Supplement Series, Vol. 155, No. 1, 11.2004, p. 73-87.

Research output: Contribution to journalArticle

Zheng, W, Mikles, VJ, Mainieri, V, Hasinger, G, Rosati, P, Wolf, C, Norman, C, Szokoly, G, Gilli, R, Tozzi, P, Wang, JX, Zirm, A & Giacconi, R 2004, 'Photometric redshift of X-ray sources in the Chandra Deep Field-South', Astrophysical Journal, Supplement Series, vol. 155, no. 1, pp. 73-87. https://doi.org/10.1086/424385
Zheng W, Mikles VJ, Mainieri V, Hasinger G, Rosati P, Wolf C et al. Photometric redshift of X-ray sources in the Chandra Deep Field-South. Astrophysical Journal, Supplement Series. 2004 Nov;155(1):73-87. https://doi.org/10.1086/424385
Zheng, W. ; Mikles, V. J. ; Mainieri, V. ; Hasinger, G. ; Rosati, P. ; Wolf, C. ; Norman, C. ; Szokoly, G. ; Gilli, R. ; Tozzi, P. ; Wang, J. X. ; Zirm, A. ; Giacconi, R. / Photometric redshift of X-ray sources in the Chandra Deep Field-South. In: Astrophysical Journal, Supplement Series. 2004 ; Vol. 155, No. 1. pp. 73-87.
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abstract = "Based on the photometry of 10 near-ultraviolet, optical, and near-infrared bands of the Chandra Deep Field-South, we estimate the photometric redshifts for 342 X-ray sources, which constitute ∼99{\%} of all the detected X-ray sources in the field. The models of spectral energy distribution are based on galaxies and a combination of power-law continuum and emission lines. Color information is useful for source classifications: type I active galactic nuclei (AGNs) show nonthermal spectral features that are distinct from galaxies and type II AGNs. The hardness ratio in X-ray and the X-ray-to-optical flux ratio are also useful discriminators. Using rudimentary color separation techniques, we are able to further refine our photometric redshift estimations. Among these sources, 173 have reliable spectroscopic redshifts, which we use to verify the accuracy of photometric redshifts and to modify the model inputs. The average relative dispersion in redshift distribution is ∼8{\%}, among the most accurate for photometric surveys. The high reliability of our results is attributable to the high quality and broad coverage of data as well as the applications of several independent methods and a careful evaluation of every source. We apply our redshift estimations to study the effect of redshift on broadband colors and to study the redshift distribution of AGNs. Our results show that both the hardness ratio and U - K color decline with redshift, which may be the result of a K-correction. The number of type II AGNs declines significantly at z > 2 and that of galaxies declines at z > 1. However, the distribution of type I AGNs exhibits less redshift dependence. As well, we observe a significant peak in the redshift distribution at z = 0.6. We demonstrate that our photometric redshift estimation produces a reliable database for the study of X-ray luminosity of galaxies and AGNs.",
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AU - Rosati, P.

AU - Wolf, C.

AU - Norman, C.

AU - Szokoly, G.

AU - Gilli, R.

AU - Tozzi, P.

AU - Wang, J. X.

AU - Zirm, A.

AU - Giacconi, R.

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