The XMM-Newton wide-field survey in the COSMOS field. III. Optical identification and multiwavelength properties of a large sample of X-ray-selected sources

M. Brusa, G. Zamorani, A. Comastri, G. Hasinger, Nico Cappelluti, F. Civano, A. Finoguenov, V. Mainieri, M. Salvato, C. Vignali, M. Elvis, F. Fiore, R. Gilli, C. D. Impey, S. J. Lilly, M. Mignoli, J. Silverman, J. Trump, C. M. Urry, R. BenderP. Capak, J. P. Huchra, J. P. Kneib, A. Koekemoer, A. Leauthaud, I. Lehmann, R. Massey, I. Matute, P. J. McCarthy, H. J. McCracken, J. Rhodes, N. Z. Scoville, Y. Taniguchi, D. Thompson

Research output: Contribution to journalArticle

127 Citations (Scopus)

Abstract

We present the optical identification of a sample of 695 X-ray sources detected in the first 1.3 deg 2 of the COSMOS XMM-Newton survey, down to a 0.5-2 keV (2-10 keV) limiting flux of ∼10 -15 erg cm -2 s -1 (∼5 × 10 -15 erg cm -2 s -1). In order to identify the correct optical counterparts and to assess the statistical significance of the X-ray - to - optical associations we have used the "likelihood ratio technique." Here we present the identification method and its application to the CFHT I-band and photometric catalogs. We were able to associate a candidate optical counterpart to ∼90% (626) of the X-ray sources, while for the remaining ∼10% of the sources we were not able to provide a unique optical association due to the faintness of the possible optical counterparts (I AB > 25) or to the presence of multiple optical sources, with similar likelihoods of being the correct identification, within the XMM-Newton error circles. We also cross-correlated the candidate optical counterparts with the Subaru multicolor and ACS catalogs and with the Magellan/IMACS, zCOSMOS, and literature spectroscopic data; the spectroscopic sample comprises 248 objects (∼40% of the full sample). Our analysis of this statistically meaningful sample of X-ray sources reveals that for ∼80% of the counterparts there is a very good agreement between the spectroscopic classification, the morphological parameters as derived from ACS data, and the optical - to - near-infrared colors: the large majority of spectroscopically identified broad-line active galactic nuclei (BL AGNs) have a pointlike morphology on ACS data, blue optical colors in color-color diagrams, and an X-ray - to - optical flux ratio typical of optically selected quasars. Conversely, sources classified as narrow line AGNs or normal galaxies are on average associated with extended optical sources, have significantly redder optical - to - near-infrared colors, and span a larger range of X-ray - to - optical flux ratios. However, about 20% of the sources show an apparent mismatch between the morphological and spectroscopic classifications. All the "extended" BL AGNs lie at redshift < 1.5, while the redshift distribution of the full BL AGN population peaks at z ∼ 1.5. The most likely explanation is that in these objects the nuclear emission is not dominant with respect to the host galaxy emission in the observed ACS band. Our analysis also suggests that the type 2/type 1 ratio decreases toward high luminosities, in qualitative agreement with the results from X-ray spectral analysis and the most recent modeling of the X-ray luminosity function evolution.

Original languageEnglish (US)
Pages (from-to)353-367
Number of pages15
JournalAstrophysical Journal, Supplement Series
Volume172
Issue number1
DOIs
StatePublished - Oct 22 2007
Externally publishedYes

Fingerprint

XMM-Newton telescope
newton
field survey
x rays
active galactic nuclei
color
erg
catalogs
near infrared
luminosity
galaxies
color-color diagram
likelihood ratio
identification method
COSMOS
spectral analysis
quasars
spectrum analysis
diagram
modeling

Keywords

  • Galaxies: active
  • Surveys
  • X-rays: diffuse background
  • X-rays: galaxies
  • X-rays: general

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

The XMM-Newton wide-field survey in the COSMOS field. III. Optical identification and multiwavelength properties of a large sample of X-ray-selected sources. / Brusa, M.; Zamorani, G.; Comastri, A.; Hasinger, G.; Cappelluti, Nico; Civano, F.; Finoguenov, A.; Mainieri, V.; Salvato, M.; Vignali, C.; Elvis, M.; Fiore, F.; Gilli, R.; Impey, C. D.; Lilly, S. J.; Mignoli, M.; Silverman, J.; Trump, J.; Urry, C. M.; Bender, R.; Capak, P.; Huchra, J. P.; Kneib, J. P.; Koekemoer, A.; Leauthaud, A.; Lehmann, I.; Massey, R.; Matute, I.; McCarthy, P. J.; McCracken, H. J.; Rhodes, J.; Scoville, N. Z.; Taniguchi, Y.; Thompson, D.

In: Astrophysical Journal, Supplement Series, Vol. 172, No. 1, 22.10.2007, p. 353-367.

Research output: Contribution to journalArticle

Brusa, M, Zamorani, G, Comastri, A, Hasinger, G, Cappelluti, N, Civano, F, Finoguenov, A, Mainieri, V, Salvato, M, Vignali, C, Elvis, M, Fiore, F, Gilli, R, Impey, CD, Lilly, SJ, Mignoli, M, Silverman, J, Trump, J, Urry, CM, Bender, R, Capak, P, Huchra, JP, Kneib, JP, Koekemoer, A, Leauthaud, A, Lehmann, I, Massey, R, Matute, I, McCarthy, PJ, McCracken, HJ, Rhodes, J, Scoville, NZ, Taniguchi, Y & Thompson, D 2007, 'The XMM-Newton wide-field survey in the COSMOS field. III. Optical identification and multiwavelength properties of a large sample of X-ray-selected sources', Astrophysical Journal, Supplement Series, vol. 172, no. 1, pp. 353-367. https://doi.org/10.1086/516575
Brusa, M. ; Zamorani, G. ; Comastri, A. ; Hasinger, G. ; Cappelluti, Nico ; Civano, F. ; Finoguenov, A. ; Mainieri, V. ; Salvato, M. ; Vignali, C. ; Elvis, M. ; Fiore, F. ; Gilli, R. ; Impey, C. D. ; Lilly, S. J. ; Mignoli, M. ; Silverman, J. ; Trump, J. ; Urry, C. M. ; Bender, R. ; Capak, P. ; Huchra, J. P. ; Kneib, J. P. ; Koekemoer, A. ; Leauthaud, A. ; Lehmann, I. ; Massey, R. ; Matute, I. ; McCarthy, P. J. ; McCracken, H. J. ; Rhodes, J. ; Scoville, N. Z. ; Taniguchi, Y. ; Thompson, D. / The XMM-Newton wide-field survey in the COSMOS field. III. Optical identification and multiwavelength properties of a large sample of X-ray-selected sources. In: Astrophysical Journal, Supplement Series. 2007 ; Vol. 172, No. 1. pp. 353-367.
@article{15e6a54b0eed4fe396a2e023b1dce505,
title = "The XMM-Newton wide-field survey in the COSMOS field. III. Optical identification and multiwavelength properties of a large sample of X-ray-selected sources",
abstract = "We present the optical identification of a sample of 695 X-ray sources detected in the first 1.3 deg 2 of the COSMOS XMM-Newton survey, down to a 0.5-2 keV (2-10 keV) limiting flux of ∼10 -15 erg cm -2 s -1 (∼5 × 10 -15 erg cm -2 s -1). In order to identify the correct optical counterparts and to assess the statistical significance of the X-ray - to - optical associations we have used the {"}likelihood ratio technique.{"} Here we present the identification method and its application to the CFHT I-band and photometric catalogs. We were able to associate a candidate optical counterpart to ∼90{\%} (626) of the X-ray sources, while for the remaining ∼10{\%} of the sources we were not able to provide a unique optical association due to the faintness of the possible optical counterparts (I AB > 25) or to the presence of multiple optical sources, with similar likelihoods of being the correct identification, within the XMM-Newton error circles. We also cross-correlated the candidate optical counterparts with the Subaru multicolor and ACS catalogs and with the Magellan/IMACS, zCOSMOS, and literature spectroscopic data; the spectroscopic sample comprises 248 objects (∼40{\%} of the full sample). Our analysis of this statistically meaningful sample of X-ray sources reveals that for ∼80{\%} of the counterparts there is a very good agreement between the spectroscopic classification, the morphological parameters as derived from ACS data, and the optical - to - near-infrared colors: the large majority of spectroscopically identified broad-line active galactic nuclei (BL AGNs) have a pointlike morphology on ACS data, blue optical colors in color-color diagrams, and an X-ray - to - optical flux ratio typical of optically selected quasars. Conversely, sources classified as narrow line AGNs or normal galaxies are on average associated with extended optical sources, have significantly redder optical - to - near-infrared colors, and span a larger range of X-ray - to - optical flux ratios. However, about 20{\%} of the sources show an apparent mismatch between the morphological and spectroscopic classifications. All the {"}extended{"} BL AGNs lie at redshift < 1.5, while the redshift distribution of the full BL AGN population peaks at z ∼ 1.5. The most likely explanation is that in these objects the nuclear emission is not dominant with respect to the host galaxy emission in the observed ACS band. Our analysis also suggests that the type 2/type 1 ratio decreases toward high luminosities, in qualitative agreement with the results from X-ray spectral analysis and the most recent modeling of the X-ray luminosity function evolution.",
keywords = "Galaxies: active, Surveys, X-rays: diffuse background, X-rays: galaxies, X-rays: general",
author = "M. Brusa and G. Zamorani and A. Comastri and G. Hasinger and Nico Cappelluti and F. Civano and A. Finoguenov and V. Mainieri and M. Salvato and C. Vignali and M. Elvis and F. Fiore and R. Gilli and Impey, {C. D.} and Lilly, {S. J.} and M. Mignoli and J. Silverman and J. Trump and Urry, {C. M.} and R. Bender and P. Capak and Huchra, {J. P.} and Kneib, {J. P.} and A. Koekemoer and A. Leauthaud and I. Lehmann and R. Massey and I. Matute and McCarthy, {P. J.} and McCracken, {H. J.} and J. Rhodes and Scoville, {N. Z.} and Y. Taniguchi and D. Thompson",
year = "2007",
month = "10",
day = "22",
doi = "10.1086/516575",
language = "English (US)",
volume = "172",
pages = "353--367",
journal = "Astrophysical Journal, Supplement Series",
issn = "0067-0049",
publisher = "IOP Publishing Ltd.",
number = "1",

}

TY - JOUR

T1 - The XMM-Newton wide-field survey in the COSMOS field. III. Optical identification and multiwavelength properties of a large sample of X-ray-selected sources

AU - Brusa, M.

AU - Zamorani, G.

AU - Comastri, A.

AU - Hasinger, G.

AU - Cappelluti, Nico

AU - Civano, F.

AU - Finoguenov, A.

AU - Mainieri, V.

AU - Salvato, M.

AU - Vignali, C.

AU - Elvis, M.

AU - Fiore, F.

AU - Gilli, R.

AU - Impey, C. D.

AU - Lilly, S. J.

AU - Mignoli, M.

AU - Silverman, J.

AU - Trump, J.

AU - Urry, C. M.

AU - Bender, R.

AU - Capak, P.

AU - Huchra, J. P.

AU - Kneib, J. P.

AU - Koekemoer, A.

AU - Leauthaud, A.

AU - Lehmann, I.

AU - Massey, R.

AU - Matute, I.

AU - McCarthy, P. J.

AU - McCracken, H. J.

AU - Rhodes, J.

AU - Scoville, N. Z.

AU - Taniguchi, Y.

AU - Thompson, D.

PY - 2007/10/22

Y1 - 2007/10/22

N2 - We present the optical identification of a sample of 695 X-ray sources detected in the first 1.3 deg 2 of the COSMOS XMM-Newton survey, down to a 0.5-2 keV (2-10 keV) limiting flux of ∼10 -15 erg cm -2 s -1 (∼5 × 10 -15 erg cm -2 s -1). In order to identify the correct optical counterparts and to assess the statistical significance of the X-ray - to - optical associations we have used the "likelihood ratio technique." Here we present the identification method and its application to the CFHT I-band and photometric catalogs. We were able to associate a candidate optical counterpart to ∼90% (626) of the X-ray sources, while for the remaining ∼10% of the sources we were not able to provide a unique optical association due to the faintness of the possible optical counterparts (I AB > 25) or to the presence of multiple optical sources, with similar likelihoods of being the correct identification, within the XMM-Newton error circles. We also cross-correlated the candidate optical counterparts with the Subaru multicolor and ACS catalogs and with the Magellan/IMACS, zCOSMOS, and literature spectroscopic data; the spectroscopic sample comprises 248 objects (∼40% of the full sample). Our analysis of this statistically meaningful sample of X-ray sources reveals that for ∼80% of the counterparts there is a very good agreement between the spectroscopic classification, the morphological parameters as derived from ACS data, and the optical - to - near-infrared colors: the large majority of spectroscopically identified broad-line active galactic nuclei (BL AGNs) have a pointlike morphology on ACS data, blue optical colors in color-color diagrams, and an X-ray - to - optical flux ratio typical of optically selected quasars. Conversely, sources classified as narrow line AGNs or normal galaxies are on average associated with extended optical sources, have significantly redder optical - to - near-infrared colors, and span a larger range of X-ray - to - optical flux ratios. However, about 20% of the sources show an apparent mismatch between the morphological and spectroscopic classifications. All the "extended" BL AGNs lie at redshift < 1.5, while the redshift distribution of the full BL AGN population peaks at z ∼ 1.5. The most likely explanation is that in these objects the nuclear emission is not dominant with respect to the host galaxy emission in the observed ACS band. Our analysis also suggests that the type 2/type 1 ratio decreases toward high luminosities, in qualitative agreement with the results from X-ray spectral analysis and the most recent modeling of the X-ray luminosity function evolution.

AB - We present the optical identification of a sample of 695 X-ray sources detected in the first 1.3 deg 2 of the COSMOS XMM-Newton survey, down to a 0.5-2 keV (2-10 keV) limiting flux of ∼10 -15 erg cm -2 s -1 (∼5 × 10 -15 erg cm -2 s -1). In order to identify the correct optical counterparts and to assess the statistical significance of the X-ray - to - optical associations we have used the "likelihood ratio technique." Here we present the identification method and its application to the CFHT I-band and photometric catalogs. We were able to associate a candidate optical counterpart to ∼90% (626) of the X-ray sources, while for the remaining ∼10% of the sources we were not able to provide a unique optical association due to the faintness of the possible optical counterparts (I AB > 25) or to the presence of multiple optical sources, with similar likelihoods of being the correct identification, within the XMM-Newton error circles. We also cross-correlated the candidate optical counterparts with the Subaru multicolor and ACS catalogs and with the Magellan/IMACS, zCOSMOS, and literature spectroscopic data; the spectroscopic sample comprises 248 objects (∼40% of the full sample). Our analysis of this statistically meaningful sample of X-ray sources reveals that for ∼80% of the counterparts there is a very good agreement between the spectroscopic classification, the morphological parameters as derived from ACS data, and the optical - to - near-infrared colors: the large majority of spectroscopically identified broad-line active galactic nuclei (BL AGNs) have a pointlike morphology on ACS data, blue optical colors in color-color diagrams, and an X-ray - to - optical flux ratio typical of optically selected quasars. Conversely, sources classified as narrow line AGNs or normal galaxies are on average associated with extended optical sources, have significantly redder optical - to - near-infrared colors, and span a larger range of X-ray - to - optical flux ratios. However, about 20% of the sources show an apparent mismatch between the morphological and spectroscopic classifications. All the "extended" BL AGNs lie at redshift < 1.5, while the redshift distribution of the full BL AGN population peaks at z ∼ 1.5. The most likely explanation is that in these objects the nuclear emission is not dominant with respect to the host galaxy emission in the observed ACS band. Our analysis also suggests that the type 2/type 1 ratio decreases toward high luminosities, in qualitative agreement with the results from X-ray spectral analysis and the most recent modeling of the X-ray luminosity function evolution.

KW - Galaxies: active

KW - Surveys

KW - X-rays: diffuse background

KW - X-rays: galaxies

KW - X-rays: general

UR - http://www.scopus.com/inward/record.url?scp=35348890725&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=35348890725&partnerID=8YFLogxK

U2 - 10.1086/516575

DO - 10.1086/516575

M3 - Article

AN - SCOPUS:35348890725

VL - 172

SP - 353

EP - 367

JO - Astrophysical Journal, Supplement Series

JF - Astrophysical Journal, Supplement Series

SN - 0067-0049

IS - 1

ER -