We present reliable multiwavelength identifications and high-quality photometric redshifts for the 462 X-ray sources in the ≈2 Ms Chandra Deep Field-South (CDF-S) survey. Source identifications are carried out using deep optical-to-radio multiwavelength catalogs, and are then combined to create lists of primary and secondary counterparts for the X-ray sources. We identified reliable counterparts for 442 (95.7%) of the X-ray sources, with an expected false-match probability of ≈ 6.2%; we also selected four additional likely counterparts. The majority of the other 16 X-ray sources appear to be off-nuclear sources, sources associated with galaxy groups and clusters, high-redshift active galactic nuclei (AGNs), or spurious X-ray sources. A likelihood-ratio method is used for source matching, which effectively reduces the false-match probability at faint magnitudes compared to a simple error-circle matching method. We construct a master photometric catalog for the identified X-ray sources including up to 42 bands of UV-to-infrared data, and then calculate their photometric redshifts (photo-z’s). High accuracy in the derived photo-z’s is accomplished owing to (1) the up-to-date photometric data covering the full spectral energy distributions (SEDs) of the X-ray sources, (2) more accurate photometric data as a result of source deblending for ≈10% of the sources in the infrared bands and a few percent in the optical and near-infrared bands, (3) a set of 265 galaxy, AGN, and galaxy/AGN hybrid templates carefully constructed to best represent all possible SEDs, (4) the Zurich Extragalactic Bayesian Redshift Analyzer used to derive the photo-z’s, which corrects the SED templates to best represent the SEDs of real sources at different redshifts and thus improves the photo-z quality. The reliability of the photo-z’s is evaluated using the subsample of 220 sources with secure spectroscopic redshifts. We achieve an accuracy of |Δz|/(1 + z) ≈ 1% and an outlier [with |Δz|/(1 + z) > 0.15] fraction of ≈1.4% for sources with spectroscopic redshifts. We performed blind tests to derive a more realistic estimate of the photo-z quality for sources without spectroscopic redshifts. We expect there are ≈9% outliers for the relatively brighter sources (R 26), and the outlier fraction will increase to ≈15%–25% for the fainter sources (R 26). The typical photo-z accuracy is ≈6%–7%. The outlier fraction and photo-z accuracy do not appear to have a redshift dependence (for z ≈ 0–4). These photo-z’s appear to be the best obtained so far for faint X-ray sources, and they have been significantly (50%) improved compared to previous estimates of the photo-z’s for the X-ray sources in the ≈2 Ms Chandra Deep Field-North and ≈1 Ms CDF-S.

Luo B., Brandt W.N., Xue Y., Brusa M., Alexander D.M., Bauer F.E., et al. (2010). Identifications and photometric redshifts of the 2Ms Chandra Deep Field-South Sources. ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 187, 560-580 [10.1088/0067-0049/187/2/560].

Identifications and photometric redshifts of the 2Ms Chandra Deep Field-South Sources

BRUSA, MARCELLA;VIGNALI, CRISTIAN
2010

Abstract

We present reliable multiwavelength identifications and high-quality photometric redshifts for the 462 X-ray sources in the ≈2 Ms Chandra Deep Field-South (CDF-S) survey. Source identifications are carried out using deep optical-to-radio multiwavelength catalogs, and are then combined to create lists of primary and secondary counterparts for the X-ray sources. We identified reliable counterparts for 442 (95.7%) of the X-ray sources, with an expected false-match probability of ≈ 6.2%; we also selected four additional likely counterparts. The majority of the other 16 X-ray sources appear to be off-nuclear sources, sources associated with galaxy groups and clusters, high-redshift active galactic nuclei (AGNs), or spurious X-ray sources. A likelihood-ratio method is used for source matching, which effectively reduces the false-match probability at faint magnitudes compared to a simple error-circle matching method. We construct a master photometric catalog for the identified X-ray sources including up to 42 bands of UV-to-infrared data, and then calculate their photometric redshifts (photo-z’s). High accuracy in the derived photo-z’s is accomplished owing to (1) the up-to-date photometric data covering the full spectral energy distributions (SEDs) of the X-ray sources, (2) more accurate photometric data as a result of source deblending for ≈10% of the sources in the infrared bands and a few percent in the optical and near-infrared bands, (3) a set of 265 galaxy, AGN, and galaxy/AGN hybrid templates carefully constructed to best represent all possible SEDs, (4) the Zurich Extragalactic Bayesian Redshift Analyzer used to derive the photo-z’s, which corrects the SED templates to best represent the SEDs of real sources at different redshifts and thus improves the photo-z quality. The reliability of the photo-z’s is evaluated using the subsample of 220 sources with secure spectroscopic redshifts. We achieve an accuracy of |Δz|/(1 + z) ≈ 1% and an outlier [with |Δz|/(1 + z) > 0.15] fraction of ≈1.4% for sources with spectroscopic redshifts. We performed blind tests to derive a more realistic estimate of the photo-z quality for sources without spectroscopic redshifts. We expect there are ≈9% outliers for the relatively brighter sources (R 26), and the outlier fraction will increase to ≈15%–25% for the fainter sources (R 26). The typical photo-z accuracy is ≈6%–7%. The outlier fraction and photo-z accuracy do not appear to have a redshift dependence (for z ≈ 0–4). These photo-z’s appear to be the best obtained so far for faint X-ray sources, and they have been significantly (50%) improved compared to previous estimates of the photo-z’s for the X-ray sources in the ≈2 Ms Chandra Deep Field-North and ≈1 Ms CDF-S.
2010
Luo B., Brandt W.N., Xue Y., Brusa M., Alexander D.M., Bauer F.E., et al. (2010). Identifications and photometric redshifts of the 2Ms Chandra Deep Field-South Sources. ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 187, 560-580 [10.1088/0067-0049/187/2/560].
Luo B.; Brandt W.N.; Xue Y.; Brusa M.; Alexander D.M.; Bauer F.E.; Comastri A.; Koekemoer A.; Lehmer B.D.; Mainieri V.; Rafferty D.A.; Schneider D.P.;...espandi
File in questo prodotto:
Eventuali allegati, non sono esposti

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/88440
 Attenzione

Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo

Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 137
  • ???jsp.display-item.citation.isi??? 131
social impact