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NUCOSMOSFC - NuSTAR COSMOS Field X-Ray Source Catalog

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Overview

To provide the census of the sources contributing to the X-ray background peak above 10 keV, the Nuclear Spectroscopic Telescope Array (NuSTAR) is performing extragalactic surveys using a three-tier "wedding cake" approach. In their paper, the authors present the NuSTAR survey of the COSMOS field, the medium sensitivity, and medium area "tier",covering 1.7 deg2 and overlapping with both Chandra and XMM-Newton data. This survey consists of 121 NuSTAR observations for a total exposure of ~3 Ms. To fully exploit these data, the authors developed a new detection strategy, carefully tested through extensive simulations. The survey sensitivity at 20% completeness is 5.9, 2.9, and 6.4 x 10-14 erg cm-2 s-1 in the 3-24, 3-8 and 8-24 keV bands, respectively. By combining detections in 3 bands, the survey consists of a sample of 91 NuSTAR sources with luminosities ~ 1042 - 1045.5 erg s-1and redshifts z ~ 0.04-2.5. Thirty-two sources are detected in the 8-24 keV band with fluxes ~100 times fainter than sources detected by Swift-BAT. Of the 91 detections, all but 4 are associated with a Chandra and/or XMM-Newton point-like counterpart. One source is associated with an extended lower energy X-ray source. The authors present the X-ray (hardness ratio and luminosity)and optical-to-X-ray properties. The observed fraction of candidate Compton-thick active galactic nuclei measured from the hardness ratio is between 13% - 20%. In their paper, the authors discuss the spectral properties of the source named NuSTAR J100259+0220.5 (source number 330) at a redshift z = 0.044, which has the highest hardness ratio in the entire sample. The measured column density exceeds 1024 cm-2, implying the source is Compton-thick. This source was not previously recognized as such without the data at energies >10 keV.

Catalog Bibcode

2015ApJ...808..185C

References

The Nustar Extragalactic Surveys: Overview and Catalog from the COSMOS Field.

    Civano F., Hickox R.C., Puccetti S., Comastri A., Mullaney J.R.,
    Zappacosta L., LaMassa S.M., Aird J., Alexander D.M., Ballantyne D.R.,
    Bauer F.E., Brandt W.N., Boggs S.E., Christensen F.E., Craig W.W.,
    Del-Moro A., Elvis M., Forster K., Gandhi P., Grefenstette B.W.,
    Hailey C.J., Harrison F.A., Lansbury G.B., Luo B., Madsen K., Saez C.,
    Stern D., Treister E., Urry M.C., Wik D.R., Zhang W.
   <Astrophys. J., 808, 185 (2015)>
   =2015ApJ...808..185C

Provenance

This table was created by the HEASARC in August 2015 based on the the machine-readable versions of Table 5 (the COSMOS Field NuSTAR source catalog) that was obtained from the ApJ web site.

Parameters

Source_Number
A unique identification number for each source in the catalog. The sources are listed in order of their detection: first those detected in the 3-24 keV band, followed by those detected in the 3-8 keV band only, and then by those detected in the 8-24 keV band only.

Name
The NuSTAR source designation, following the standard IAU convention using the J2000.0 source position and the prefix 'NuSTAR', e.g., 'NuSTAR J095815+0149.5'.

RA
The Right Ascension of the NuSTAR X-ray source in the selected equinox. This was given in J2000.0 decimal degrees to a precision of 10-6 degrees (0.0036 arcseconds) in the original table.

Dec
The Declination of the NuSTAR X-ray source in the selected equinox. This was given in J2000.0 decimal degrees to a precision of 10-6 degrees (0.0036 arcseconds) in the original table.

LII
The Galactic Longitude of the NuSTAR X-ray source.

BII
The Galactic Latitude of the NuSTAR X-ray source.

BB_Detect_Likelihood
The 3-24 keV band detection maximum likelihood, DET_ML, for the source using the deblended source and background counts. The DET_ML is related to the Poisson probability that a source candidate is a random fluctuation of the background (Prandom), where DET_ML = -ln (Prandom). Sources with low values of DET_ML, and correspondingly high values of Prandom, are likely to be background fluctuations.

BB_Exposure
The 3-24 keV band exposure time at the position of the source, in seconds.

BB_Total_Counts
The 3-24 keV band total counts in a 20 arcseconds radius circular aperture at the position obtained by SExtractor.

BB_Dblend_Bck_Counts
The 3-24 keV band deblended background counts within a 20 arcseconds radius aperture in the background mosaic.

BB_Nodblend_Bck_Counts
The 3-24 keV band not deblended background counts within a 20 arcseconds radius aperture in the background mosaic.

BB_Counts
The 3-24 keV band net counts (deblended if detected or 3-sigma upper limit if not) in a 20-arcsecond-radius circular aperture at the position obtained by SExtractor. The authors used the procedure described by Mullaney et al.(2015 ApJ, 808, 184; their Section 2.3.2) to deblend the counts of sources that have been possibly contaminated by objects at separations of 90 arcseconds or lower. Deblended source and background counts were used to compute new DET_ML values for each source.

BB_Counts_Error
The error in the net 3-24 keV band source counts computed using the Gehrels statistic (Gehrels 1986, ApJ, 303, 336).

BB_Count_Rate_Limit
This limit flag parameter is set to '<' if the corresponding parameter value is a 90% upper limit rather than a detection.

BB_Count_Rate
The 3-24 keV band count rate (deblended if detected or 3-sigma upper limit if not) in a 20-arcsecond-radius circular aperture at the position obtained by SExtractor, in counts per second. Vignetting-corrected count rates for each source were obtained by dividing the best-fit counts derived from aperture photometry for each band by the net exposure time, weighted by the vignetting at the position of each source.

BB_Flux_Limit
This limit flag parameter is set to '<' if the corresponding parameter value is a 90% upper limit rather than a detection.

BB_Flux
The aperture-corrected 3-24 keV band flux of the source (or the 90% confidence upper limit for sources not detected in this band), in erg s-1 cm-2. Fluxes for the 3-8 and 8-24 keV bands were computed using a power-law model with slope Gamma = 1.8, the typical value for AGNs in this energy range (Burlon et al. 2011, ApJ, 728, 58; Alexander et al. 2013, ApJ, 773, 125), and a Galactic column density NH = 2.6 x 1020 cm-2 (Kalberla et al. 2005, A&A, 440, 775). The counts-to-flux conversion factors (CF) adopted here, computed using the response matrix and ancillary file available in the adopted CALDB, are CF = 4.59, 3.22 and 6.64 x 10-11 erg cm-2 counts-1 in the 3-24, 3-8 and 8-24 keV bands, respectively.

BB_Flux_Error
The error in the aperture-corrected 3-24 keV band flux of the source, in erg s-1 cm-2.

SB_Detect_Likelihood
The 3-8 keV band detection maximum likelihood, DET_ML, for the source using the deblended source and background counts. The DET_ML is related to the Poisson probability that a source candidate is a random fluctuation of the background (Prandom), where DET_ML = -ln (Prandom). Sources with low values of DET_ML, and correspondingly high values of Prandom, are likely to be background fluctuations.

SB_Exposure
The 3-8 keV band exposure time at the position of the source, in seconds.

SB_Total_Counts
The 3-8 keV band total counts in a 20 arcseconds radius circular aperture at the position obtained by SExtractor.

SB_Dblend_Bck_Counts
The 3-8 keV band deblended background counts within a 20 arcseconds radius aperture in the background mosaic.

SB_Nodblend_Bck_Counts
The 3-8 keV band not deblended background counts within a 20 arcseconds radius aperture in the background mosaic.

SB_Counts
The 3-8 keV band net counts (deblended if detected or 3-sigma upper limit if not) in a 20-arcsecond-radius circular aperture at the position obtained by SExtractor. The authors used the procedure described by Mullaney et al.(2015 ApJ, 808, 184; their Section 2.3.2) to deblend the counts of sources that have been possibly contaminated by objects at separations of 90 arcseconds or lower. Deblended source and background counts were used to compute new DET_ML values for each source.

SB_Counts_Error
The error in the net 3-8 keV band source counts computed using the Gehrels statistic (Gehrels 1986, ApJ, 303, 336).

SB_Count_Rate_Limit
This limit flag parameter is set to '<' if the corresponding parameter value is a 90% upper limit rather than a detection.

SB_Count_Rate
The 3-8 keV band count rate (deblended if detected or 3-sigma upper limit if not) in a 20-arcsecond-radius circular aperture at the position obtained by SExtractor, in counts per second. Vignetting-corrected count rates for each source were obtained by dividing the best-fit counts derived from aperture photometry for each band by the net exposure time, weighted by the vignetting at the position of each source.

SB_Flux_Limit
This limit flag parameter is set to '<' if the corresponding parameter value is a 90% upper limit rather than a detection.

SB_Flux
The aperture-corrected 3-8 keV band flux of the source (or the 90% confidence upper limit for sources not detected in this band), in erg s-1 cm-2. Fluxes for the 3-8 and 8-24 keV bands were computed using a power-law model with slope Gamma = 1.8, the typical value for AGNs in this energy range (Burlon et al. 2011, ApJ, 728, 58; Alexander et al. 2013, ApJ, 773, 125), and a Galactic column density NH = 2.6 x 1020 cm-2 (Kalberla et al. 2005, A&A, 440, 775).The counts-to-flux conversion factors (CF) adopted here, computed using the response matrix and ancillary file available in the adopted CALDB, are CF = 4.59, 3.22 and 6.64 x 10-11 erg cm-2 counts-1 in the 3-24, 3-8 and 8-24 keV bands, respectively.

SB_Flux_Error
The error in the aperture-corrected 3-8 keV band flux of the source, in erg s-1 cm-2.

HB_Detect_Likelihood
The 8-24 keV band detection maximum likelihood, DET_ML, for the source using the deblended source and background counts. The DET_ML is related to the Poisson probability that a source candidate is a random fluctuation of the background (Prandom), where DET_ML = -ln (Prandom). Sources with low values of DET_ML, and correspondingly high values of Prandom, are likely to be background fluctuations.

HB_Exposure
The 8-24 keV band exposure time at the position of the source, in seconds.

HB_Total_Counts
The 8-24 keV band total counts in a 20 arcseconds radius circular aperture at the position obtained by SExtractor.

HB_Dblend_Bck_Counts
The 8-24 keV band deblended background counts within a 20 arcseconds radius aperture in the background mosaic.

HB_Nodblend_Bck_Counts
The 8-24 keV band not deblended background counts within a 20-arcsecond-radius aperture in the background mosaic.

HB_Counts
The 8-24 keV band net counts (deblended if detected or 3-sigma upper limit if not) in a 20-arcsecond-radius circular aperture at the position obtained by SExtractor. The authors used the procedure described by Mullaney et al.(2015 ApJ, 808, 184; their Section 2.3.2) to deblend the counts of sources that have been possibly contaminated by objects at separations of 90 arcseconds or lower. Deblended source and background counts were used to compute new DET_ML values for each source.

HB_Counts_Error
The error in the net 8-24 keV band source counts computed using the Gehrels statistic (Gehrels 1986, ApJ, 303, 336).

HB_Count_Rate_Limit
This limit flag parameter is set to '<' if the corresponding parameter value is a 90% upper limit rather than a detection.

HB_Count_Rate
The 8-24 keV band count rate (deblended if detected or 3-sigma upper limit if not) in a 20-arcsecond-radius circular aperture at the position obtained by SExtractor, in counts per second. Vignetting-corrected count rates for each source were obtained by dividing the best-fit counts derived from aperture photometry for each band by the net exposure time, weighted by the vignetting at the position of each source.

HB_Flux_Limit
This limit flag parameter is set to '<' if the corresponding parameter value is a 90% upper limit rather than a detection.

HB_Flux
The aperture-corrected 8-24 keV band flux of the source (or the 90% confidence upper limit for sources not detected in this band), in erg s-1 cm-2. Fluxes for the 3-8 and 8-24 keV bands were computed using a power-law model with slope Gamma = 1.8, the typical value for AGNs in this energy range (Burlon et al. 2011, ApJ, 728, 58; Alexander et al. 2013, ApJ, 773, 125), and a Galactic column density NH = 2.6 x 1020 cm-2 (Kalberla et al. 2005, A&A, 440, 775).The counts-to-flux conversion factors (CF) adopted here, computed using the response matrix and ancillary file available in the adopted CALDB, are CF = 4.59, 3.22 and 6.64 x 10-11 erg cm-2 counts-1 in the 3-24, 3-8 and 8-24 keV bands, respectively.

HB_Flux_Error
The error in the aperture-corrected 8-24 keV band flux of the source, in erg s-1 cm-2.

Hardness_Ratio
The hardness ratio of the NuSTAR X-ray source, defined as HR = (H-S)/(H+S), where H and S are the number of net counts in a 20 arcseconds radius circular aperture in the 8-24 and 3-8 bands, respectively. The authors used the Bayesian Estimation of Hardness Ratios method (BEHR, Park et al. 2006, ApJ, 652, 610) which is the most suitable tool to compute hardness ratios and uncertainties in the Poisson regime of low counts, whether the source is detected in both bands or not. The HR reported in the catalog is the mode value computed by BEHR.

Hardness_Ratio_Neg_Err
The negative error in the hardness ratio of the NuSTAR X-ray source. The errors computed with BEHR were estimated using the Gibbs sampler (a special case of the MCMC) to obtain information on the posterior distribution of the 3-8 and 8-24 keV counts and therefore on the HR (see Park et al. 2006 for more details). The errors and the upper and lower limits on the HR are derived from the MCMC draws. The limits do not necessarily correspond to a non-detection in a given band, because BEHR computes the value of HR directly using total counts and background counts, and relies on the combined statistics of both sub-bands.

Hardness_Ratio_Pos_Err
The positive error in the hardness ratio of the NuSTAR X-ray source. The errors computed with BEHR were estimated using the Gibbs sampler (a special case of the MCMC) to obtain information on the posterior distribution of the 3-8 and 8-24 keV counts and therefore on the HR (see Park et al. 2006 for more details). The errors and the upper and lower limits on the HR are derived from the MCMC draws. The limits do not necessarily correspond to a non-detection in a given band, because BEHR computes the value of HR directly using total counts and background counts, and relies on the combined statistics of both sub-bands.

Band_Ratio
The band ratio of the NuSTAR X-ray source, defined as R = S/H, where H and S are the number of net counts in a 20 arcseconds radius circular aperture in the 8-24 and 3-8 bands, respectively. The authors used the Bayesian Estimation of Hardness Ratios method (BEHR, Park et al. 2006, ApJ, 652, 610) which is the most suitable tool to compute band ratios and uncertainties in the Poisson regime of low counts, whether the source is detected in both bands or not

Band_Ratio_Neg_Err
The negative error in the band ratio of the NuSTAR X-ray source computed with BEHR.

Band_Ratio_Pos_Err
The positive error in the band ratio of the NuSTAR X-ray source computed with BEHR.

CCOSMOS_Source_Number
The Chandra-COSMOS (C-COSMOS) identification number of the lower-energy counterpart to the NuSTAR source, from Elvis et al. (2009, ApJS, 184, 158). The authors used the nearest neighbor matching approach to find counterparts, with a 30 arcseconds matching radius. Given that the NuSTAR survey overlaps also with the new Chandra COSMOS Legacy survey (F. Civano et al. 2015, in preparation), they also used the Chandra catalog for this project (S. Marchesi et al.2015, in preparation). They applied a flux cut to both catalogs at 5 x 10-15 erg cm-2 s-1 (2-10 keV), consistent with the limit in flux used in their simulations. At this flux, the number density of sources in the 2-10 keV band is 600 deg-2, therefore the number of Chandra or XMM-Newton sources found by chance in the searching area around each NuSTAR source is <0.13. All the matches reported in this catalog are therefore very likely to be real associations.

XCOSMOS_Source_Number
The XMM-COSMOS identification number of the lower-energy counterpart to the NuSTAR source, from Brusa et al. (2010, ApJ, 716, 348). The authors used the nearest neighbor matching approach to find counterparts, with a 30 arcseconds matching radius.

CXOXMM_RA
The Right Ascension of the Chandra or XMM-Newton counterpart to the NuSTAR source in the selected equinox. This was given in J2000.0 decimal degrees to a precision of 10-6 degrees (0.0036 arcseconds) in the original table.

CXOXMM_Dec
The Declination of the Chandra or XMM-Newton counterpart to the NuSTAR source in the selected equinox. This was given in J2000.0 decimal degrees to a precision of 10-6 degrees (0.0036 arcseconds) in the original table.

CXOXMM_SB_Flux_Limit
This limit flag parameter is set to '<' if the corresponding parameter value is a 90% upper limit rather than a detection.

CXOXMM_SB_Flux
The aperture-corrected 0.5-2 keV band flux of the Chandra counterpart to the NuSTAR source, or if there is none, of the XMM-Newton counterpart to the NuSTAR source, in erg s-1 cm-2.

CXOXMM_HB_Flux
The aperture-corrected 2-10 keV band flux of the Chandra counterpart to the NuSTAR source, or if there is none, of the XMM-Newton counterpart to the NuSTAR source, in erg s-1 cm-2.

Redshift
The spectroscopic redshift of the C-COSMOS or XMM-COSMOS counterpart to the NuSTAR source.

Spectroscopic_Type
The spectroscopic source type classification:

    Value   Meaning

      1     Broad-line AGN
      2     Narrow emission-line AGN
  

Phot_Redshift
The photometric redshift of the C-COSMOS or XMM-COSMOS counterpart to the NuSTAR source.

Photometric_Type
The photometric source type classification (see Civano et al. (2012, ApJS, 201, 30) for details).:

    Value   Meaning

      1     Unobscured AGN
      2     Obscured AGN
  

NuSTAR_CXOXMM_Offset
The angular offset, in arcseconds, between the NuSTAR source position and that of the Chandra or XMM_Newton counterpart.

Spec_Luminosity_Distance
The luminosity distance to the source using the Spectroscopic redshift, in Mpc.

Phot_Luminosity_Distance
The luminosity distance to the source using the photometric redshift, in Mpc.

Log_BB_Luminosity_Limit
This limit flag parameter is set to '<' if the corresponding parameter value is a 90% upper limit rather than a detection.

Log_BB_Luminosity
The logarithm of the 3-24 keV band luminosity of the source, in erg s-1, or 90% upper limit thereof, if undetected.

Log_SB_Luminosity_Limit
This limit flag parameter is set to '<' if the corresponding parameter value is a 90% upper limit rather than a detection.

Log_SB_Luminosity
The logarithm of the 3-8 keV band luminosity of the source, in erg s-1, or 90% upper limit thereof, if undetected.

Log_HB_Luminosity_Limit
This limit flag parameter is set to '<' if the corresponding parameter value is a 90% upper limit rather than a detection.

Log_HB_Luminosity
The logarithm of the 8-24 keV band luminosity of the source, in erg s-1, or 90% upper limit thereof, if undetected.

Mult_LE_Ctrpart_Flag
This flag parameter is set to 1 if there are multiple lower energy counterparts to the NuSTAR source; otherwise, it is set to 0. Among the 87 sources with a Chandra and/or XMM-Newton counterpart, 14 have multiple matches within 30 arcseconds. The distribution of separations considering the secondary counterpart (defining as secondary the source at larger separation) is shown in Figure 10 of the reference paper. Two of the NuSTAR sources with a multiple match show a significant iron K-alpha line in the NuSTAR spectrum at the energy as expected from the redshift of the primary Chandra and/or XMM-Newton counterpart, therefore these sources (NuSTAR J100142+0203.8 and J100259+0220.6, source numbers 181 and 330 in the catalog) can be securely associated with their lower energy counterparts. Of the 12 remaining NuSTAR sources with multiple lower energy X-ray counterparts, only two (NuSTAR J095845+0149.0 and J095935+0241.3, source numbers 134 and 257) have a primary and secondary counterpart with separations and fluxes in the 2-10 keV Chandra/XMM-Newton band within 3% of each other; therefore both primary and secondary could be considered a possible association in these two cases. For ten of the 14 sources with two possible counterparts, the separation between the NuSTAR position and the secondary candidate is 30% larger than the separation between the NuSTAR position and the primary. The flux of the secondary is also significantly fainter (50% or more) than the primary, making the primary association stronger. Therefore, the authors considered the primary match to be the Chandra and/or XMM-Newton counterpart in these 10 cases.


Contact Person

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Page Author: Browse Software Development Team
Last Modified: 24-Aug-2015