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ECDFSOID2 - Extended Chandra Deep Field-South Optical and Near-IR Counterparts

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Overview

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 (L0.5-8keV ~ 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 (Rmag ~ 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.

Catalog Bibcode

2010ApJS..191..124S

References

 The Extended Chandra Deep Field-South Survey: Optical spectroscopy
 of faint X-ray sources with the VLT and Keck
     Silverman J.D., Mainieri V., Salvato M., Hasinger G., Bergeron J.,
     Capak P., Szokoly G., Finoguenov A., Gilli R., Rosati P., Tozzi P.,
     Vignali C., Alexander D.M., Brandt W.N., Lehmer B.D., Luo B.,
     Rafferty D., Xue Y.Q., Balestra I., Bauer F.E., Brusa M., Comastri A.,
     Kartaltepe J., Koekemoer A.M., Miyaji T., Schneider D.P., Treister E.,
     Wisotski L., Schramm M.
    <Astrophys. J. Suppl. 191, 124-142 (2010)>
    =2010ApJS..191..124S

Provenance

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.

Parameters

Source_Number
The source number, a unique identifier in order of ascending J2000 Right Ascension, for E-CDF-S X-ray sources listed in Table 2 (the main catalog) of the Lehmer et al. (2005, ApJS, 161, 21) Chandra source catalog.

Name
The recommended source designation for objects in this catalog, based on the IAU-registered 'CXOECDFS' prefix for 'Chandra X-ray Observatory Extended Chandra Deep Field-South' and the J2000 X-ray source position. Source Designation. This was not provided in the reference paper but was obtained from the Lehmer et al. (2005, ApJS, 161, 21) E-CDF-S Chandra source catalog using the source_number parameter (q.v.).

RA
The Right Ascension of the optical/near-infrared counterpart to the E-CDF-S source in the selected equinox. This was given in J2000.0 decimal degrees to a precision of 10-5 degrees (0.036 arcseconds) in the original reference.

Dec
The Declination of the optical/near-infrared counterpart to the E-CDF-S source in the selected equinox. This was given in J2000.0 decimal degrees to a precision of 10-5 degrees (0.036 arcseconds) in the original reference.

LII
The Galactic Longitude of the optical/near-infrared counterpart to the E-CDF-S source.

BII
The Galactic Latitude of the optical/near-infrared counterpart to the E-CDF-S source.

OIR_Catalog
The catalog associated with the identified counterpart: ACS-z (GOODS-z or GEMS-z; z-band HST/ACS catalog), WFI-R (WFI R-band catalog), SOFI-K (K-band catalog from SOFI), ISAAC-K (K-band catalog from VLT/ISAAC), SOFI-H (H-band catalog from SOFI).

Offset
The separation in arcseconds between the X-ray source and its counterpart.

Likelihood_Ratio
The likelihood ratio, or the probability that the given optical or near-IR source is the true counterpart to the X-ray source, relative to the chance that the same object is a random background source. The calculation and meaning of this parameter is discussed in Section 2 of the reference paper.

ID_Reliability
The reliability parameter Rj for the optical/near-IR source being the true counterpart to the X-ray source, as defined in Section 2 of the reference paper.

Rmag
The R-band (AB) magnitude of the optical/near-infrared counterpart to the E-CDF-S source.

Redshift
The spectroscopic redshift of the optical/near-infrared counterpart to the E-CDF-S source.

Redshift_Flag
The quality flag for the spectroscopic redshift, with 2 meaning 'secure', 1 that there is some uncertainty and 0 that there is no spectroscopic redshift value. A value of 0.5 is added to this number if the spectroscopic redshift is in agreement with the photometric redshift.

Spect_Catalog
The corresponding spectroscopic catalog, as follows:

      1 = Szokoly et al. (2004, ApJS, 155, 271);
      2 = FORS2/GOODS;
      3 = VVDS;
      5 = New VLT;
      6 = VIMOS/GOODS;
      7 = K20;
     10 = New Keck (2007-2008);
     11 = Ravikumar et al. (2007);
     12 = New VLT/9hr;
     13 = Treister et al. (2009, ApJ, 696, 110);
     14 = Wisotzki/Schramm, private communication;
     15 = New Keck (2010).
  

Broad_Type
The spectroscopic classification of the optical/near-infrared counterpart to the E-CDF-S source: BLAGN, NELG, ALG or STAR. These are determined by the presence of spectral features that fall within the observed optical window thus:

     1. Broad emission-line AGN (BLAGN): Presence of at least one emission line
  having FWHM > 2000 km s-1

     2. Narrow emission-line galaxy (NELG): Presence of at least one emission
  line having FWHM < 2000 km s-1 and no BLAGN signatures.

     3. Absorption-line galaxy (ALG): No emission lines with an observed
  equivalent width EQW > 5 Angstroms, clear signs of absorption lines such as
  Ca H+K, Mg II, or the G band.

     4. Star.
  
The authors note that there are a handful of objects where the classification depended on the observed spectral window. For example, they initially classified the optical spectra of a few cases as ALG or NELG based on VIMOS/MR coverage with observed wavelength above 5500 Angstoms, but changed the classification to BLAGN due to the presence of broad Mg II falling at shorter wavelengths in VIMOS/LR spectra.

Phot_Redshift
The photometric redshift of the optical/near-infrared counterpart to the E-CDF-S source, taken from Rafferty et al. (2010, in preparation) or Luo et al. (2010, ApJS, 187, 560).

Phot_Redshift_Neg_Err
The lower uncertainty in the value of the photometric redshift.

Phot_Redshift_Pos_Err
The upper uncertainty in the value of the photometric redshift.

Class
The HEASARC Browse object classification of the optical/near-infrared counterpart to the E-CDF-S source, based on the value of the broad_type parameter.


Contact Person

Questions regarding the ECDFSOID2 database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 10-Nov-2010