This table contains the redshift catalog for the X-ray sources detected in the Chandra Lockman Area North Survey (CLANS). The redshifts for the CLANS field are all new. For fluxes above 10^-14 ergs cm^-2 s^-1 (2-8 keV) the authors have redshifts for 76% of the sources in the CLANS, CLASXS, and CDF-N surveys. They extend the redshift information for the full sample using photometric redshifts. The goal of the OPTX Project is to use these three surveys, which are among the most spectroscopically complete surveys to date, to analyze the effect of spectral type on the shape and evolution of the X-ray luminosity functions and to compare the optical spectral types with the X-ray spectral properties. The optical and infrared photometric catalog for the CLANS X-ray sources is presented here (see the CLANS Browse table for the X-ray information). The CLANS and CLASXS surveys bridge the gap between the ultra-deep pencil-beam surveys, such as the CDFs, and the shallower, very large-area surveys. As a result, they probe the X-ray sources that contribute the bulk of the 2-8 keV X-ray background and cover the flux range of the observed break in the log N - log S distribution. This table was created by the HEASARC in December 2008 based on the electronic version of Table 11 from the paper which was obtained from the ApJ web site. This is a service provided by NASA HEASARC .

This table contains the first results of the authors' optical spectroscopy program aimed to provide redshifts and identifications for the X-ray sources in the Extended Chandra Deep Field South (ECDFS). A total of 339 sources (listed herein) were targeted using the IMACS spectrograph at the Magellan telescopes and the VIMOS spectrograph at the VLT. The authors have measured redshifts for 186 X-ray sources, including archival data and a literature search. They find that the active galactic nucleus (AGN) host galaxies have on average redder rest-frame optical colors than nonactive galaxies, and that they live mostly in the "green valley." The dependence of the fraction of AGNs that are obscured on both luminosity and redshift is confirmed at high significance and the observed AGN spatial density is compared with the expectations from existing luminosity functions. These AGNs show a significant difference in the mid-IR to X-ray flux ratio for obscured and unobscured AGNs, which can be explained by the effects of dust self-absorption on the former. This difference is larger for lower luminosity sources, which is consistent with the dust opening angle depending on AGN luminosity. This table was created by the HEASARC in April 2009 based on the electronic version of Table 2 from the Treister et al. (2009) paper obtained from the ApJ web site, except for the source positions which were taken from Virani et al. (2006). The full table from the latter paper is also available in Browse (the ECDFSCXO table). This is a service provided by NASA HEASARC .

In their paper, the authors release accurate photometric redshifts for 1692 counterparts to Chandra sources in the central square degree of the Cosmic Evolution Survey (COSMOS) field. The availability of a large training set of spectroscopic redshifts that extends to faint magnitudes enabled photometric redshifts comparable to the highest quality results presently available for normal galaxies. The authors demonstrate that morphologically extended, faint X-ray sources without optical variability are more accurately described by a library of normal galaxies (corrected for emission lines) than by active galactic nucleus (AGN) dominated templates, even if these sources have AGNlike X-ray luminosities. Preselecting the library on the bases of the source properties allowed them to reach an accuracy sigma[Delta-z/(1+Z_spec)] ~ 0.015 with a fraction of outliers of 5.8% for the entire Chandra-COSMOS sample. In addition, in this study the authors released revised photometric redshifts for the 1735 optical counterparts of the XMM-detected sources over the entire 2 deg² of COSMOS (these sources are listed in the HEASARC table XMMCPHOTZ). For 248 sources, their updated photometric redshift differs from the previous release by Delta-z > 0.2. These changes are predominantly due to the inclusion of newly available deep H-band^ photometry (H_AB = 24 mag). The authors illustrate once again the importance of a spectroscopic training sample and how an assumption about the nature of a source together, with the number and the depth of the available bands, influences the accuracy of the photometric redshifts determined for AGN. These considerations should be kept in mind when defining the observational strategies of upcoming large surveys targeting AGNs, such as eROSITA at X-ray energies and the Australian Square Kilometre Array Pathfinder Evolutionary Map of the Universe in the radio band. This table contains the photometric redshifts and related quantities for 1694 (note that there appears to be 2 more sources than the above-quoted abstract states) Chandra sources in the central square degree of the COSMOS field. Notice that in the original as-published paper no positional information was provided. The HEASARC has assumed that the source numbers used in the present catalog are in the same source numbering scheme as used by Elvis et al. (2009, ApJS, 184, 158, the Chandra COSMOS Survey Point Source Catalog, available at the HEASARC as the CCOSMOSCAT table) and thus obtained the positions and (position-based) names corresponding to these sources. This table was created by the HEASARC in November 2011 based on an electronic version of Table 4 from the reference paper which was obtained from the ApJ website. This is a service provided by NASA HEASARC .

In their paper, the authors release accurate photometric redshifts for 1692 counterparts to Chandra sources in the central square degree of the Cosmic Evolution Survey (COSMOS) field. The availability of a large training set of spectroscopic redshifts that extends to faint magnitudes enabled photometric redshifts comparable to the highest quality results presently available for normal galaxies. The authors demonstrate that morphologically extended, faint X-ray sources without optical variability are more accurately described by a library of normal galaxies (corrected for emission lines) than by active galactic nucleus (AGN) dominated templates, even if these sources have AGNlike X-ray luminosities. Preselecting the library on the bases of the source properties allowed them to reach an accuracy sigma[Delta-z/(1+Z_spec)] ~ 0.015 with a fraction of outliers of 5.8% for the entire Chandra-COSMOS sample. These Chandra sources are not contained in this table but are available in the HEASARC table CCOSMPHOTZ). In addition, in this study the authors released revised photometric redshifts for the 1735 optical counterparts of the XMM-detected sources over the entire 2 deg² of COSMOS, and these are the sources listed in the present table. For 248 sources, their updated photometric redshift differs from the previous release by Delta-z > 0.2. These changes are predominantly due to the inclusion of newly available deep H-band^ photometry (H_AB = 24 mag). The authors illustrate once again the importance of a spectroscopic training sample and how an assumption about the nature of a source together, with the number and the depth of the available bands, influences the accuracy of the photometric redshifts determined for AGN. These considerations should be kept in mind when defining the observational strategies of upcoming large surveys targeting AGNs, such as eROSITA at X-ray energies and the Australian Square Kilometre Array Pathfinder Evolutionary Map of the Universe in the radio band. This table contains the photometric redshifts and related quantities for 1735 XMM-Newton sources over the entire 2 square degrees of the COSMOS field. Notice that in the original as-published paper no positional information was provided. The HEASARC has assumed that the source numbers used in the present catalog are in the same source numbering scheme as used by Cappelluti et al. (2009, A&A, 497, 635, the XMM-Newton Wide-Field Survey in the COSMOS Field Point-like X-ray Source Catalog, available at the HEASARC as the XMMCOSMOS table) and thus obtained the positions and (position-based) names corresponding to these X-ray sources from the latter. This table was created by the HEASARC in November 2011 based on an electronic version of Table 5 from the reference paper which was obtained from the ApJ website. This is a service provided by NASA HEASARC .

This table contains the X-ray point-source catalog produced from the Chandra Advanced CCD Imaging Spectrometer (ACIS-I) observations of the combined ~3.2 deg² DEEP2 (XDEEP2) survey fields, which consist of four ~ 0.7 - 1.1 deg² fields. The combined total exposures across all four XDEEP2 fields range from ~ 10 ks to 1.1 Ms. The authors detect X-ray point sources in both the individual ACIS-I observations and the overlapping regions in the merged (stacked) images. They find a total of 2976 unique X-ray sources within the survey area with an expected false-source contamination of ~ 30 sources (<~ 1%). In their paper, the authors present the combined log N-log S distribution of sources detected across the XDEEP2 survey fields and find good agreement with the Extended Chandra Deep Field and Chandra-COSMOS fields to f_(X,0.5-2keV)_ ~ 2 x 10^-16 erg cm^-1 s^-1. Given the large survey area of XDEEP2, they additionally place relatively strong constraints on the log N-log S distribution at high fluxes (f_(X,0.5-2keV) ~ 3 x 10^-14 erg cm^-1 s^-1), and find a small systematic offset (a factor ~ 1.5) toward lower source numbers in this regime, when compared to smaller area surveys. The number counts observed in XDEEP2 are in close agreement with those predicted by X-ray background synthesis models. Additionally, the authors present a Bayesian-style method for associating the X-ray sources with optical photometric counterparts in the DEEP2 catalog (complete to R_AB < 25.2) and find that 2126 (~ 71.4% +/- 2.8%) of the 2976 X-ray sources presented here have a secure optical counterpart with a <~ 6% contamination fraction. The present table provides the DEEP2 optical source properties (e.g., magnitude, redshift) as part of the X-ray-optical counterpart catalog. This table was created by the HEASARC in October 2012 based on electronic versions of Tables 5 and 7 from the reference paper which were obtained from the ApJS web site. This is a service provided by NASA HEASARC .

This table contains the catalogs for the X-ray sources detected in the Chandra Lockman Area North Survey (CLANS). (The information on the optical and infrared counterparts to these sources is contained in the CLANSOID table.) The nine ACIS-I fields which constitute the CLANS cover a solid angle of ~0.6 deg² and reach fluxes of 7 x 10^-16 ergs cm^-2 s^-1 (0.5-2 keV) and 3.5 x 10^-15 ergs cm^-2 s^-1 (2-8 keV). The authors find a total of 761 X-ray point sources. The CLANS and CLASXS surveys bridge the gap between the ultra-deep pencil-beam surveys, such as the CDFs, and the shallower, very large-area surveys. As a result, they probe the X-ray sources that contribute the bulk of the 2-8 keV X-ray background and cover the flux range of the observed break in the log N-log S distribution. CLANS consists of nine separate 70 ks Chandra ACIS-I exposures centered at J2000.0 RA and Dec of (10 46,+59 01) (see Table 2 of the reference paper for the full observational details) which were combined to create an 0.6 deg² image containing 761 sources. The CLANS observations consist of a raster with an ~2 arcminute overlap between contiguous pointings. Following the prescription in Yang et al. (2004, AJ, 128, 1501) for the CLASXS field, the authors merged the nine individual pointing catalogs to create the final CLANS X-ray catalog. For sources with more than one detection in the nine fields, they used the detection from the observation in which the effective area of the source was the largest. This table was created by the HEASARC in December 2008 based on the electronic versions of Tables 4 and 5 from the paper which were obtained from the ApJ web site. This is a service provided by NASA HEASARC .

This table contains the results of a program to acquire high-quality optical spectra of X-ray sources detected in the Extended-Chandra Deep Field-South (E-CDF-S) and its central 2 Ms area. New spectroscopic redshifts, up to z = 4, are measured for 283 counterparts to Chandra sources with deep exposures (t ~ 2-9 hr per pointing) using multi-slit facilities on both VLT (VIMOS) and Keck (DEIMOS), thus bringing the total number of spectroscopically identified X-ray sources to over 500 in this survey field. Since their new spectroscopic identifications are mainly associated with X-ray sources in the shallower 250 ks coverage, the authors provide a comprehensive catalog of X-ray sources detected in the E-CDF-S including the optical and near-infrared counterparts, determined by a likelihood routine, and redshifts (both spectroscopic and photometric), that incorporate published spectroscopic catalogs, thus resulting in a final sample with a high fraction (80%) of X-ray sources having secure identifications. The authors demonstrate the remarkable coverage of the luminosity-redshift plane now accessible from their data while emphasizing the detection of active galactic nuclei (AGNs) that contribute to the faint end of the luminosity function (L_0.5-8keV ~ 10⁴³ - 10⁴⁴ erg s^-1) at 1.5 <~ z <~ 3, including those with and without broad emission lines. This redshift catalog includes 17 type-2 QSOs at 1 <~ z <~ 3.5 that significantly increases (doubles) such samples. Based on thei deepest (9 hr) VLT/VIMOS observation, the authors identify "elusive" optically faint galaxies (R_mag ~ 25) at z ~ 2 - 3 based upon the detection of interstellar absorption lines (e.g., O II+Si IV, C II], C IV); in their paper, they highlight one such case, an absorption-line galaxy at z = 3.208 having no obvious signs of an AGN in its optical spectrum. In addition, they determine accurate distances to eight galaxy groups with extended X-ray emission detected both by Chandra and XMM-Newton. This online catalog was created by the HEASARC in November 2010 based on a machine-readable version of Table 4 from the paper which was obtained from the ApJ website. This is a service provided by NASA HEASARC .