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EROSXMM - Extremely Red Objects XMM-Newton Survey Catalog

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Overview

This table contains the results of a deep (about 80 ks) XMM-Newton survey of the largest sample of near-infrared-selected Extremely Red Objects (R-K > 5) available to date to K_s < ~19.2. At the relatively bright X-ray fluxes ((F(2-10 keV) >~ 4 x 10^-15 erg cm^-2 s^-1) and near-infrared magnitude probed by the present observations, the fraction of AGN (i.e. X-ray detected) among the ERO population is small (~3.5%); conversely, the fraction of EROs among hard X-ray selected sources is much higher (~20%). The X-ray properties of the 9 EROs detected in this XMM-Newton observation indicate absorption in excess of 10^22 cm^-2 in a large fraction of them. The X-ray, optical and near-infrared properties of those X-ray selected EROs with a spectroscopic or photometric redshift nicely match those expected for type 2 quasars, the high-luminosity, high-redshift obscured AGNs predicted in baseline XRB synthesis models. A close correlation is detected between X-ray and K-band fluxes.

This table contains the X-ray and optical information for the sources detected in the sum of 3 separate XMM-Newton observations of a field centered on 14 49 25, +09 00 13 (J2000.0 RA and Dec) known as the "Daddi" field (Daddi et al. 2000, A&A, 361, 535) in which 257 EROs are known to be present. The data from all 3 EPIC instruments (PN, MOS1 and MOS2) obtained in the 3 observations was combined, yielding a total exposure time for the PN of ~82 ks, and for the MOS instruments of ~78 ks. The X-ray hardness ratio (HR) and the optical to near-infrared color (R and K magnitudes) are reported for all the detected X-ray sources and their counterparts, along with the reliability of the X-ray to optical or near-infrared associations as measured by the likelihood ratios, LR(R) and LR(K). This table lists data for the 111 proposed optical/infrared counterparts for the 97 detected X-ray sources, i.e., X-ray sources with more than one possible optical/IR counterpart will have multiple entries in this table, one for each counterpart, as follows: 73 X-ray sources have secure optical/near-IR counterparts (counterpart_status=1), 7 X-ray sources have 2 possible 'likely' counterparts, and 1 X-ray source has 3 such counterparts (counterpart_status=2), 6 X-ray sources have only low-likelihood counterparts all of which lie outside the 3" matching radii (counterpart_status=3), and the remaining 9 X-ray sources lack optical and infrared photometry (counterpart_status=4).


Catalog Bibcode

2005A&A...432...69B

References

XMM-Newton observations of Extremely Red Objects and the link with luminous,
X-ray obscured quasars.
    Brusa M., Comastri A., Daddi E., Pozzetti L., Zamorani G., Vignali C.,
    Cimatti A., Fiore F., Mignoli M., Ciliegi P., Rottgering H.J.A.
   <Astron. Astrophys. 432, 69 (2005)>
   =2005A&A...432...69B

Provenance

This table was created by the HEASARC in February 2007 based on the CDS Catalog J/A+A/432/69 files table1.dat and table2.dat.

Parameters

Source_Number
A unique X-ray source identifier, apparently from the source detection algorithm. Since only sources which were detected above a detection probability threshold of 2 x 10^-5 (which corresponds to less than 1 spurious X-ray source, or a ~4-sigma Gaussian threshold) were retained in the final list, the source numbers for the 87 X-ray sources are not contiguous, but range from 23 to 370.

Name
The name for the X-ray source using the '[BCD2005]' prefix (for Brusa, Comastri and Daddi 2005) and the source number value, as recommended by the CDS Dictionary of Nomenclature of Celestial Objects.

RA
The Right Ascension of the X-ray source centroid in the selected equinox. This was given in J2000.0 decimal degree coordinates to a precision of 10^-5 degrees in Table 1 of the reference paper. The X-ray centroids were astrometrically calibrated with respect to the optical positions of three bright quasars in the field: the resulting shift of ~2" (including a shift of +1.47" in RA) was applied to all the source positions.

Dec
The Declination of the X-ray source centroid in the selected equinox. This was given in J2000.0 decimal degree coordinates to a precision of 10^-5 degrees in Table 1 of the reference paper. The X-ray centroids were astrometrically calibrated with respect to the optical positions of three bright quasars in the field: the resulting shift of ~2" (including a shift of -1.29" in Declination) was applied to all the source positions.

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

HB_Flux
The hard-band (2 - 10 keV) X-ray flux of the source, in erg/cm^2/s. The count rate to flux conversion factor was derived assuming a power law with a photon index Gamma of 1.7, absorbed by the Galactic column density in the direction of the Daddi field N_H of 5 x 10^20 atoms cm^-2 (Dickey and Lockman 1990, ARA&A, 28, 215), and weighted by the effective exposure times of the different EPIC cameras. The uncertainty in the derived fluxes is <15% for Delta(Gamma) = +/- 0.5 and N_H up to 10^21 atoms cm^-2. The corresponding full-band limiting flux is ~2 x 10^-15 erg/cm^2/s at the aim point and is a factor of ~1.5 times higher at the edge of the selected area, where the net exposure is ~40 ks. If the source was not detected in this band, no value is given for this flux.

HB_Counts_Limit
This parameter is set to '<' if the source was not detected in the hard band.

HB_Counts
The X-ray source counts in the hard band (2 - 10 keV), or the 3-sigma upper limit if the source was not detected in this band, i.e., if the corresponding limit parameter value is '<'.

HB_Counts_Error
The rms uncertainty in the X-ray source hard counts.

SB_Flux
The soft-band (0.5 - 2 keV) X-ray flux of the source, in erg/cm^2/s. The count rate to flux conversion factor was derived assuming a power law with a photon index Gamma of 1.7, absorbed by the Galactic column density in the direction of the Daddi field N_H of 5 x 10^20 atoms cm^-2 (Dickey and Lockman 1990, ARA&A, 28, 215), and wighted by the effective exposure times of the different EPIC cameras. The uncertainty in the derived fluxes is <15% for Delta(Gamma) = +/- 0.5 and N_H up to 10^21 atoms cm^-2. The corresponding full-band limiting flux is ~2 x 10^-15 erg/cm^2/s at the aim point and is a factor of ~1.5 times higher at the edge of the selected area, where the net exposure is ~40 ks. If the source was not detected in this band, no value is given for this flux.

SB_Counts_Limit
This parameter is set to '<' if the source was not detected in the soft band.

SB_Counts
The X-ray source counts in the soft band (0.5 - 2 keV), or the 3-sigma upper limit if the source was not detected in this band, i.e., if the corresponding limit parameter value is '<'.

SB_Counts_Error
The rms uncertainty in the X-ray source soft counts.

Counterpart_Status
The reliability status of the association of the optical/IR object with the X-ray source, coded as follows:

  1 = sources with secure X-ray to optical associations
  2 = sources with ambiguous X-ray to optical associations
  3 = sources with low X-ray to optical likelihood ratio
  4 = sources without optical/near infrared photometry
  

The methodology used to estimate the counterpart status is discussed in Section 2.4 of the reference paper. Of the 111 proposed optical/infrared counterparts for the 97 detected X-ray sources, i.e., X-ray sources with more than one possible optical/IR counterpart will have multiple entries in this table, one for each counterpart, as follows: 73 X-ray sources have secure optical/near-IR counterparts (counterpart_status=1), 7 X-ray sources have 2 possible 'likely' counterparts, and 1 X-ray source has 3 such counterparts (counterpart_status=2), 6 X-ray sources have only low-likelihood counterparts all of which lie outside the 3" matching radii (counterpart_status=3), and the remaining 9 X-ray sources lack optical and infrared photometry (counterpart_status=4).

Offset
The angular offset between the possible optical/IR counterpart and the X-ray source, in arcseconds.

Rmag
The R-band magnitude (in the AB system) of the possible optical/IR counterpart to the X-ray source detected within a radius of 3" around the X-ray source.

Kmag_Limit
This parameter is set to '<' if the K magnitude is an upper limit.

Kmag
The K-band magnitude (in the AB system) of the possible optical/IR counterpart to the X-ray source detected within a radius of 3" around the X-ray source.

R_Band_Likelihood
The likelihood ratio LR(R) in the R-band, defined as the ratio of the probablity that the optical/IR source is the correct identification for the x-ray source to the corresponding probability that it is an unrelated background object. This should be compared with the threshold value LR_th(R) = 0.25 which discriminates between spurious (<0.25) and real (>0.25) identifications (see Section 2.3 of the reference paper for more details).

K_Band_Likelihood
The likelihood ratio LR(K) in the K-band, defined as the ratio of the probablity that the optical/IR source is the correct identification for the x-ray source to the corresponding probability that it is an unrelated background object. This should be compared with the threshold value LR_th(K) = 0.25 which discriminates between spurious (<0.25) and real (>0.25) identifications (see Section 2.3 of the reference paper for more details).


Contact Person

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

Page Author: Browse Software Development Team
Last Modified: 28-Feb-2007