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SSA22CXO - SSA22 Field Chandra X-Ray Point Source Catalog

HEASARC
Archive

Overview

This table contains the main X-ray point-source catalog for a deep ~400-ks Chandra ACIS-I (Advanced CCD Imaging Spectrometer) exposure of the SSA22 field. The observations were centred on a z = 3.09 protocluster, which is populated by Lyman break galaxies (LBGs), Lyman-alpha emitters (LAEs) and extended Lyman-alpha-emitting blobs (LABs). The survey reached ultimate (3 count) sensitivity limits of ~5.7 x 10-17 and ~3.0 x 10-16 erg cm-2 s-1 for the 0.5-2 and 2-8 keV bands, respectively (corresponding to L(2-10 keV) ~ 5.7 x 1042 erg s-1 and L(10-30 keV) ~ 2.0 x 1043 erg s-1 at z = 3.09, respectively, for an assumed photon index of Gamma = 1.4). These limits make SSA22 the fourth deepest extragalactic Chandra survey yet conducted, and the only one focused on a known high-redshift structure. In total, the authors detect 297 X-ray point sources and identify one obvious bright extended X-ray source (not included in the current table) over a ~330 arcmin2 region. In addition to the X-ray data, the authors provide all available optical spectroscopic redshifts and near-infrared and mid-infrared photometry available for their sources. The basic X-ray and infrared properties of their Chandra sources indicate a variety of source types, although absorbed active galactic nuclei (AGN) appear to dominate. In total, they have identified 12 X-ray sources (either via optical spectroscopic redshifts or LAE selection) at z = 3.06 - 3.12 that are likely to be associated with the SSA22 protocluster. These sources have X-ray and multiwavelength properties that suggest they are powered by AGN with 0.5 - 8 keV luminosities in the range of ~ 1043 - 1045 erg s-1. The authors have analysed the AGN fraction of sources in the protocluster as a function of local LAE source density and find suggestive evidence for a correlation between AGN fraction and local LAE source density (at the ~96 per cent confidence level), implying that supermassive black hole growth at z ~3 is strongest in the highest density regions.

Catalog Bibcode

2009MNRAS.400..299L

References

The Chandra Deep Protocluster Survey: Point Source Catalogues for a 400-ks
Observation of the z = 3.09 Protocluster in SSA22
    Lehmer B.D., Alexander D.M., Chapman S.C., Smail I., Bauer F.E.,
    Brandt W.N., Geach J.E., Matsuda Y., Mullaney J.R., Swinbank A.M.
   <Monthly Notices Royal Astron. Soc. 400, 299-316 (2009)>
   =2009MNRAS.400..299L

Provenance

This table was created by the HEASARC in February 2010 based on the electronic version of Table 2 from the reference paper which was obtained from the Monthly Notices web site.

Parameters

Source_Number
The X-ray source number. Sources are listed in order of increasing J2000.0 right ascension. Source positions were determined following the procedure discussed in Section 3.2.1 of the reference paper.

Alt_Name
An alternative catalog-based source designation using the precepts of the Dictionary of Nomenclature of Celestial Objects using the [LAC2009] prefix for Lehmer, Alexander, Chapman 2009 and the source number.

Name
The source designation as stated by the authors using the prefix 'CXOSSA22' (for Chandra X-ray Observatory Small Selected Area 22) and the J2000.0 RA and Dec truncated to 0.1 seconds of time and 1 arcsecond, respectively.

RA
The Right Ascension of the Chandra source in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.01 seconds of time in the original table. Source positions were determined following the procedure discussed in Section 3.2.1 of the reference paper.

Dec
The Declination of the Chandra source in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.1 arcseconds in the original table. Source positions were determined following the procedure discussed in Section 3.2.1 of the reference paper.

LII
The Galactic Longitude of the Chandra source.

BII
The Galactic Latitude of the Chandra source.

Ae_Detect_Prob
The ACIS Extract (AE) significance, presented as unity minus the computed binomial probability P that no X-ray source exists (1 - P). #

Log_Min_Wavdetect_Prob
The ACIS Extract (AE) significance, presented as the logarithm of the minimum false-positive probability run with WAVDETECT in which each source was detected. Lower values of the binomial probability and false-positive probability threshold indicate a more significant source detection. The authors find that 189, 20, 30 and 58 sources have minimum WAVDETECT false-positive probability thresholds of 10-8, 10-7, 10-6 and 10-5, respectively.

Error_Radius
The 80 percent positional uncertainty of the X-ray source, in arcseconds, computed following equation (1) in the reference paper, which is dependent on the off-axis angle and the net counts of the source in the detection band used to determine the photometric properties.

Off_Axis
The off-axis angle for the X-rayu source, in arcminutes. This is calculated using the X-ray source position and the exposure-weighted mean aim point. The aimpoints of the 4 individual Chandra observations used in this study are given in Table 1 of the reference paper.

FB_Counts_Limit
This limit flag for the full-band counts is set to '<' if the source was not detected in this band. All upper limits were computed using the AE-extracted photometry (see Section 3.2.1 of the reference paper) and correspond to the 3-sigma level appropriate for Poisson statistics (Gehrels 1986, ApJ, 303, 336).

FB_Counts
The net background-subtracted source counts in the standard full band (0.5-8.0 keV). Source counts and their associated statistical errors have been calculated by AE using the given X-ray position (ra and dec parameters) for all bands and following the methods discussed in detail in Section 3.2.1 of the reference paper, and have not been corrected for vignetting. The authors note that the extraction of source counts and the computation of statistical errors was performed for all sources in their candidate-list catalog of sources detected using WAVDETECT at a false-positive probability threshold of 1 x 10-5. Since all candidate-list catalog sources were masked when calculating local backgrounds for their main catalog sources listed in this HEASARC table (see Section 3.2.1 of the reference paper), this could in principle have a mild effect on background calculations in cases where lower significance candidate-list catalog sources (i.e. sources that would later not be included in the main catalog) were near main catalog sources. The authors note, however, that since the number of candidate-list catalog sources that were excluded from the main catalog is small (i.e. 53 sources), there is little overlap between these sources and the background extraction regions of their main catalog. They found that 43 (~14%) of the 297 main catalog background extraction regions had some overlap with the ~90% PSF regions of at least one of the 53 excluded candidate-list catalog sources. Since the 53 excluded candidate-list catalog sources already have count estimates that were consistent with the local background, the authors conclude that this will not have a significant effect on their main catalog source properties.

To be consistent with their point-source detection criteria defined in Section 3.2.2 of the reference paper, the authors considered a source to be 'detected' for photometry purposes in a given band if the AE-computed binomial probability for that band has a value of P <0.01. When a source is not detected in a given band, an upper limit is calculated; these sources are indicated with values of '<' for the corresponding limit parameter.

FB_Counts_Pos_Err
The 1-sigma upper statistical error in the full-band source counts using the Gehrels (1986, ApJ, 303, 336) prescription.

FB_Counts_Neg_Err
The 1-sigma lower statistical error in the full-band source counts using the Gehrels (1986, ApJ, 303, 336) prescription.

SB_Counts_Limit
This limit flag for the soft-band counts is set to '<' if the source was not detected in this band. All upper limits were computed using the AE-extracted photometry (see Section 3.2.1 of the reference paper) and correspond to the 3-sigma level appropriate for Poisson statistics (Gehrels 1986, ApJ, 303, 336).

SB_Counts
The net background-subtracted source counts in the standard soft band (0.5-2.0 keV). Source counts and their associated statistical errors have been calculated by AE using the given X-ray position (ra and dec parameters) for all bands and following the methods discussed in detail in Section 3.2.1 of the reference paper, and have not been corrected for vignetting. The authors note that the extraction of source counts and the computation of statistical errors was performed for all sources in their candidate-list catalog of sources detected using WAVDETECT at a false-positive probability threshold of 1 x 10-5. Since all candidate-list catalog sources were masked when calculating local backgrounds for their main catalog sources listed in this HEASARC table (see Section 3.2.1 of the reference paper), this could in principle have a mild effect on background calculations in cases where lower significance candidate-list catalog sources (i.e. sources that would later not be included in the main catalog) were near main catalog sources. The authors note, however, that since the number of candidate-list catalog sources that were excluded from the main catalog is small (i.e. 53 sources), there is little overlap between these sources and the background extraction regions of their main catalog. They found that 43 (~14%) of the 297 main catalog background extraction regions had some overlap with the ~90% PSF regions of at least one of the 53 excluded candidate-list catalog sources. Since the 53 excluded candidate-list catalog sources already have count estimates that were consistent with the local background, the authors conclude that this will not have a significant effect on their main catalog source properties.

To be consistent with their point-source detection criteria defined in Section 3.2.2 of the reference paper, the authors considered a source to be 'detected' for photometry purposes in a given band if the AE-computed binomial probability for that band has a value of P <0.01. When a source is not detected in a given band, an upper limit is calculated; these sources are indicated with values of '<' for the corresponding limit parameter.

SB_Counts_Pos_Err
The 1-sigma upper statistical error in the soft-band source counts using the Gehrels (1986, ApJ, 303, 336) prescription.

SB_Counts_Neg_Err
The 1-sigma lower statistical error in the soft-band source counts using the Gehrels (1986, ApJ, 303, 336) prescription.

HB_Counts_Limit
This limit flag for the hard-band counts is set to '<' if the source was not detected in this band. All upper limits were computed using the AE-extracted photometry (see Section 3.2.1 of the reference paper) and correspond to the 3-sigma level appropriate for Poisson statistics (Gehrels 1986, ApJ, 303, 336).

HB_Counts
The net background-subtracted source counts in the standard hard band (2.0-8.0 keV). Source counts and their associated statistical errors have been calculated by AE using the given X-ray position (ra and dec parameters) for all bands and following the methods discussed in detail in Section 3.2.1 of the reference paper, and have not been corrected for vignetting. The authors note that the extraction of source counts and the computation of statistical errors was performed for all sources in their candidate-list catalog of sources detected using WAVDETECT at a false-positive probability threshold of 1 x 10-5. Since all candidate-list catalog sources were masked when calculating local backgrounds for their main catalog sources listed in this HEASARC table (see Section 3.2.1 of the reference paper), this could in principle have a mild effect on background calculations in cases where lower significance candidate-list catalog sources (i.e. sources that would later not be included in the main catalog) were near main catalog sources. The authors note, however, that since the number of candidate-list catalog sources that were excluded from the main catalog is small (i.e. 53 sources), there is little overlap between these sources and the background extraction regions of their main catalog. They found that 43 (~14%) of the 297 main catalog background extraction regions had some overlap with the ~90% PSF regions of at least one of the 53 excluded candidate-list catalog sources. Since the 53 excluded candidate-list catalog sources already have count estimates that were consistent with the local background, the authors conclude that this will not have a significant effect on their main catalog source properties.

To be consistent with their point-source detection criteria defined in Section 3.2.2 of the reference paper, the authors considered a source to be 'detected' for photometry purposes in a given band if the AE-computed binomial probability for that band has a value of P <0.01. When a source is not detected in a given band, an upper limit is calculated; these sources are indicated with values of '<' for the corresponding limit parameter.

HB_Counts_Pos_Err
The 1-sigma upper statistical error in the hard-band source counts using the Gehrels (1986, ApJ, 303, 336) prescription.

HB_Counts_Neg_Err
The 1-sigma lower statistical error in the hard-band source counts using the Gehrels (1986, ApJ, 303, 336) prescription.

IR_RA
The right ascension of the near-IR source centroid in the selected equinox, which was obtained by matching the X-ray source positions (ra and dec parameter) to Deep Extragalactic Survey (DXS) UKIDSS K-band positions using a matching radius of 1.5 times the positional uncertainty quoted in the error_radius parameter. For five X-ray sources more than one near-IR match was found, and for these sources the source with the smallest offset was selected as the most probable counterpart. Using these criteria, 183 (~63%) of the sources have K-band counterparts. Note that the matching criterion used herein is more conservative than that used in the derivation of the positional errors (i.e. the median value of 1.5 times the positional uncertainty is ~1.3 arcsec). Sources with no optical counterparts have their K-band right ascension and declination values set to null values (they were set to 0 00 00, 0 00 00 (J2000.0) in the original table). This parameter was given in J2000.0 coordinates to a precision of 0.01 seconds of time in the original table.

IR_Dec
The Declination of the near-IR source centroid in the selected equinox, which was obtained by matching the X-ray source positions (ra and dec parameter) to Deep Extragalactic Survey (DXS) UKIDSS K-band positions using a matching radius of 1.5 times the positional uncertainty quoted in the error_radius parameter. For five X-ray sources more than one near-IR match was found, and for these sources the source with the smallest offset was selected as the most probable counterpart. Using these criteria, 183 (~63%) of the sources have K-band counterparts. Note that the matching criterion used herein is more conservative than that used in the derivation of the positional errors (i.e. the median value of 1.5 times the positional uncertainty is ~1.3 arcsec). Sources with no optical counterparts have their K-band right ascension and declination values set to null values (they were set to 0 00 00, 0 00 00 (J2000.0) in the original table). This parameter was given in J2000.0 coordinates to a precision of 0.1 arcseconds in the original table.

CXO_IR_Offset
The measured offset between the K-band and X-ray source positions, in arcseconds. Sources with no K-band counterparts have a value set to null in this HEASARC table (they were set to -1 in the original table). The authors find a median offset of 0.35 arcseconds.

Kmag
The corresponding K-band magnitude (Vega) for the near-IR source located at the position indicated in the ir_ra and ir_dec parameter. Sources with no K-band counterpart have a value set to null (they were set to -1. in the original table).

Bmag
The AB magnitude of the optical counterpart for the Subaru B optical band. Information regarding the Subaru observations can be found in section 2 of Hayashino et al. (2004, AJ, 128, 2073). The Subaru observations cover the entire Chandra observed region of SSA22 and reach 5-sigma limiting depths of B = 26.5, V = 26.6, R = 26.7, i' = 26.4 and z' = 25.7 AB magnitudes. Using a constant 1.5 arcsecond matching radius, the authors found that 175, 202, 211, 210 and 205 of the main catalogue sources had B-, V-, R-, i'- and z'-band counterparts, respectively; 213 of the main catalog sources had at least one optical counterpart. Based on the shift and rematch technique described in Section 3.2.2 of the reference paper, they estimate that ~45.8 (+6.9,-6.7) are expected to be false matches. When a counterpart is not identified for a given band, a null value is listed for that band (they were set to -1. in the original table).

Vmag
The AB magnitude of the optical counterpart for the Subaru V optical band. Information regarding the Subaru observations can be found in section 2 of Hayashino et al. (2004, AJ, 128, 2073). The Subaru observations cover the entire Chandra observed region of SSA22 and reach 5-sigma limiting depths of B = 26.5, V = 26.6, R = 26.7, i' = 26.4 and z' = 25.7 AB magnitudes. Using a constant 1.5 arcsecond matching radius, the authors found that 175, 202, 211, 210 and 205 of the main catalogue sources had B-, V-, R-, i'- and z'-band counterparts, respectively; 213 of the main catalog sources had at least one optical counterpart. Based on the shift and rematch technique described in Section 3.2.2 of the reference paper, they estimate that ~45.8 (+6.9,-6.7) are expected to be false matches. When a counterpart is not identified for a given band, a null value is listed for that band (they were set to -1. in the original table).

Rmag
The AB magnitude of the optical counterpart for the Subaru R optical band. Information regarding the Subaru observations can be found in section 2 of Hayashino et al. (2004, AJ, 128, 2073). The Subaru observations cover the entire Chandra observed region of SSA22 and reach 5-sigma limiting depths of B = 26.5, V = 26.6, R = 26.7, i' = 26.4 and z' = 25.7 AB magnitudes. Using a constant 1.5 arcsecond matching radius, the authors found that 175, 202, 211, 210 and 205 of the main catalogue sources had B-, V-, R-, i'- and z'-band counterparts, respectively; 213 of the main catalog sources had at least one optical counterpart. Based on the shift and rematch technique described in Section 3.2.2 of the reference paper, they estimate that ~45.8 (+6.9,-6.7) are expected to be false matches. When a counterpart is not identified for a given band, a null value is listed for that band (they were set to -1. in the original table).

Imag
The AB magnitude of the optical counterpart for the Subaru i' optical band. Information regarding the Subaru observations can be found in section 2 of Hayashino et al. (2004, AJ, 128, 2073). The Subaru observations cover the entire Chandra observed region of SSA22 and reach 5-sigma limiting depths of B = 26.5, V = 26.6, R = 26.7, i' = 26.4 and z' = 25.7 AB magnitudes. Using a constant 1.5 arcsecond matching radius, the authors found that 175, 202, 211, 210 and 205 of the main catalogue sources had B-, V-, R-, i'- and z'-band counterparts, respectively; 213 of the main catalog sources had at least one optical counterpart. Based on the shift and rematch technique described in Section 3.2.2 of the reference paper, they estimate that ~45.8 (+6.9,-6.7) are expected to be false matches. When a counterpart is not identified for a given band, a null value is listed for that band (they were set to -1. in the original table).

Zmag
The AB magnitude of the optical counterpart for the Subaru z' optical band. Information regarding the Subaru observations can be found in section 2 of Hayashino et al. (2004, AJ, 128, 2073). The Subaru observations cover the entire Chandra observed region of SSA22 and reach 5-sigma limiting depths of B = 26.5, V = 26.6, R = 26.7, i' = 26.4 and z' = 25.7 AB magnitudes. Using a constant 1.5 arcsecond matching radius, the authors found that 175, 202, 211, 210 and 205 of the main catalogue sources had B-, V-, R-, i'- and z'-band counterparts, respectively; 213 of the main catalog sources had at least one optical counterpart. Based on the shift and rematch technique described in Section 3.2.2 of the reference paper, they estimate that ~45.8 (+6.9,-6.7) are expected to be false matches. When a counterpart is not identified for a given band, a null value is listed for that band (they were set to -1. in the original table).

IRAC_3p6_um_Mag
The AB magnitude of the IR counterpart to the source in the Spitzer IRAC band at 3.6 microns (um). Information regarding the IRAC observations can be found in section 2.1 of Webb et al. (2009, ApJ, 692, 1561). The IRAC observations cover the majority of the Chandra-observed region of SSA22 and reach 5-sigma limiting depths of 23.6, 23.4, 21.6 and 21.5 AB magnitudes for the 3.6, 4.5, 5.8 and 8.0 um bands, respectively. Using a constant 1.5 arcsecond matching radius, the authors found that 212, 217, 173 and 174 of the main catalog sources had 3.6, 4.5, 5.8 and 8.0 um counterparts, respectively; 234 of the main catalog sources have at least one IRAC counterpart. Based on the shift and rematch technique described in Section 3.2.2 of the reference paper, the authors estimate that ~21.3 (+5.7,-4.6) are expected to be false matches. When a counterpart is not identified for a given IRAC band, a null value is listed for that band (they were set to -1. in the original table). The authors note that a small area of the Chandra exposure has no overlapping IRAC observations (see Fig. 2 of the reference paper), and sources in these regions have been given a value of -2.0 for their IRAC magnitudes in such cases.

IRAC_4p5_um_Mag
The AB magnitude of the IR counterpart to the source in the Spitzer IRAC band at 4.5 microns (um). Information regarding the IRAC observations can be found in section 2.1 of Webb et al. (2009, ApJ, 692, 1561). The IRAC observations cover the majority of the Chandra-observed region of SSA22 and reach 5-sigma limiting depths of 23.6, 23.4, 21.6 and 21.5 AB magnitudes for the 3.6, 4.5, 5.8 and 8.0 um bands, respectively. Using a constant 1.5 arcsecond matching radius, the authors found that 212, 217, 173 and 174 of the main catalog sources had 3.6, 4.5, 5.8 and 8.0 um counterparts, respectively; 234 of the main catalog sources have at least one IRAC counterpart. Based on the shift and rematch technique described in Section 3.2.2 of the reference paper, the authors estimate that ~21.3 (+5.7,-4.6) are expected to be false matches. When a counterpart is not identified for a given IRAC band, a null value is listed for that band (they were set to -1. in the original table). The authors note that a small area of the Chandra exposure has no overlapping IRAC observations (see Fig. 2 of the reference paper), and sources in these regions have been given a value of -2.0 for their IRAC magnitudes in such cases.

IRAC_5p8_um_Mag
The AB magnitude of the IR counterpart to the source in the Spitzer IRAC band at 5.8 microns (um). Information regarding the IRAC observations can be found in section 2.1 of Webb et al. (2009, ApJ, 692, 1561). The IRAC observations cover the majority of the Chandra-observed region of SSA22 and reach 5-sigma limiting depths of 23.6, 23.4, 21.6 and 21.5 AB magnitudes for the 3.6, 4.5, 5.8 and 8.0 um bands, respectively. Using a constant 1.5 arcsecond matching radius, the authors found that 212, 217, 173 and 174 of the main catalog sources had 3.6, 4.5, 5.8 and 8.0 um counterparts, respectively; 234 of the main catalog sources have at least one IRAC counterpart. Based on the shift and rematch technique described in Section 3.2.2 of the reference paper, the authors estimate that ~21.3 (+5.7,-4.6) are expected to be false matches. When a counterpart is not identified for a given IRAC band, a null value is listed for that band (they were set to -1. in the original table). The authors note that a small area of the Chandra exposure has no overlapping IRAC observations (see Fig. 2 of the reference paper), and sources in these regions have been given a value of -2.0 for their IRAC magnitudes in such cases.

IRAC_8p0_um_Mag
The AB magnitude of the IR counterpart to the source in the Spitzer IRAC band at 8.0 microns (um). Information regarding the IRAC observations can be found in section 2.1 of Webb et al. (2009, ApJ, 692, 1561). The IRAC observations cover the majority of the Chandra-observed region of SSA22 and reach 5-sigma limiting depths of 23.6, 23.4, 21.6 and 21.5 AB magnitudes for the 3.6, 4.5, 5.8 and 8.0 um bands, respectively. Using a constant 1.5 arcsecond matching radius, the authors found that 212, 217, 173 and 174 of the main catalog sources had 3.6, 4.5, 5.8 and 8.0 um counterparts, respectively; 234 of the main catalog sources have at least one IRAC counterpart. Based on the shift and rematch technique described in Section 3.2.2 of the reference paper, the authors estimate that ~21.3 (+5.7,-4.6) are expected to be false matches. When a counterpart is not identified for a given IRAC band, a null value is listed for that band (they were set to -1. in the original table). The authors note that a small area of the Chandra exposure has no overlapping IRAC observations (see Fig. 2 of the reference paper), and sources in these regions have been given a value of -2.0 for their IRAC magnitudes in such cases.

Redshift
The best available optical spectroscopic redshift for the X-ray source when the optical and X-ray positions were offset by less than 1.5 arcseconds. Spectroscopic redshifts for 46 sources are provided: 31 sources from the Garilli et al. (2008, A&A, 486, 683) catalog of the VIMOS VLT Deep Survey (VVDS; Le F`evre et al. 2005, A&A, 439, 845), two sources from the Steidel et al. (2003, ApJ, 592, 728) LBG survey, four sources from the Matsuda et al. (2005, ApJ, 634, L125) LAE survey and nine sources from a new spectroscopic campaign of Chapman et al. (in preparation). In total, nine of the sources had spectroscopic redshifts within z = 3.06-3.12 (Delta-v ~ 4000 km s-1), suggesting that they are likely members of the SSA22 protocluster (see Section 4 of the reference paper for further details). Sources with no spectroscopic redshift available have been set to a null value (they were set to -1. in the original table).

Ref_Redshift
The spectroscopic survey which was used to provide the quoted redshift value:

    1 = Garilli et al. (2008, A&A, 486, 683)
    2 = Steidel et al. (2003, ApJ, 592, 728)
    3 = Matsuda et al. (2005, ApJ, 634, L125)
    4 = Chapman et al. (in preparation)
  

Exposure
The effective exposure time (in seconds) in the full band, derived from the standard-band exposure maps (see Section 3.1 of the reference paper for details on the exposure maps). Dividing the full-band counts listed in the fb_counts parameter for a source by the corresponding effective exposure in this band will provide the vignetting-corrected and quantum efficiency degradation-corrected count rate in this band.

SB_Exposure
The effective exposure time (in seconds) in the soft band, derived from the standard-band exposure maps (see Section 3.1 of the reference paper for details on the exposure maps). Dividing the soft-band counts listed in the sb_counts parameter for a source by the corresponding effective exposure in this band will provide the vignetting-corrected and quantum efficiency degradation-corrected count rate in this band.

HB_Exposure
The effective exposure time (in seconds) in the hard band, derived from the standard-band exposure maps (see Section 3.1 of the reference paper for details on the exposure maps). Dividing the hard-band counts listed in the hb_counts parameter for a source by the corresponding effective exposure in this band will provide the vignetting-corrected and quantum efficiency degradation-corrected count rate in this band.

Band_Ratio
The band ratio for the X-ray source, defined as the ratio of counts between the hard and soft bands. Quoted band ratios have been corrected for differential vignetting between the hard band and soft band using the appropriate exposure maps. Errors for this quantity are calculated following the numerical error propagation method described in section 1.7.3 of Lyons (1991, Data Analysis for Physical Science Students); this avoids the failure of the standard approximate variance formula when the number of counts is small and has an error distribution that is non-Gaussian. Sources detected only in the full band have band ratios and corresponding errors set to null values (they were set to -1. in the original table).

Band_Ratio_Pos_Err
The upper (positive) error in the band ratio for the X-ray source. Upper limits are calculated for sources detected in the soft band but not in the hard band and lower limits are calculated for sources detected in the hard band but not in the soft band. For these sources, the upper and lower errors are set to the computed band ratio. Sources detected only in the full band have band ratios and corresponding errors set to null values (they were set to -1. in the original table).

Band_Ratio_Neg_Err
The lower (negative) error in the band ratio for the X-ray source. Upper limits are calculated for sources detected in the soft band but not in the hard band and lower limits are calculated for sources detected in the hard band but not in the soft band. For these sources, the upper and lower errors are set to the computed band ratio. Sources detected only in the full band have band ratios and corresponding errors set to null values (they were set to -1. in the original table).

Spectral_Index
The effective photon index (Gamma_eff) for a power-law model with the Galactic column density. The effective photon index has been calculated based on the value of the band ratio. For sources that are not detected (as per the definition discussed above in the description of the counts parameters) in the hard band or soft band, then lower or upper limits, respectively, are placed on Gamma_eff; in these cases, the photon index and the upper and lower errors are all set to the limiting value. When a source is only detected in the full band, then the effective photon index and upper and lower limits are all set to 1.4, a value that is representative for faint sources, and that should give reasonable fluxes.

Spectral_Index_Pos_Err
The upper (positive) error in the effective photon index (Gamma_eff) for a power-law model with the Galactic column density. For sources that are not detected (as per the definition discussed above in the description of the counts parameters) in the hard band or soft band, then lower or upper limits, respectively, are placed on Gamma_eff; in these cases, the photon index and the upper and lower errors are all set to the limiting value. When a source is only detected in the full band, then the effective photon index and upper and lower limits are all set to 1.4, a value that is representative for faint sources, and that should give reasonable fluxes.

Spectral_Index_Neg_Err
The lower (negative) error in the effective photon index (Gamma_eff) for a power-law model with the Galactic column density. For sources that are not detected (as per the definition discussed above in the description of the counts parameters) in the hard band or soft band, then lower or upper limits, respectively, are placed on Gamma_eff; in these cases, the photon index and the upper and lower errors are all set to the limiting value. When a source is only detected in the full band, then the effective photon index and upper and lower limits are all set to 1.4, a value that is representative for faint sources, and that should give reasonable fluxes.

FB_Flux_Limit
This limit flag for the full-band flux is set to '<' if the source was not detected in this band, and the quoted value is an upper limit rather than a detection.

FB_Flux
The observed-frame flux of the X-ray source in the standard full band; quoted fluxes are in units of erg cm-2 s-1. Fluxes have been computed using the fb_counts, and the corresponding exposure time and spectral slope value given in the spectral_index parameter. If fb_flux_limit is '<', then the quoted value is an upper limit rather than a detection. The fluxes have been corrected for absorption by the Galaxy but have not been corrected for material intrinsic to the source. For a power-law model with Gamma = 1.4, the soft-band and hardband Galactic absorption corrections are ~12.6% and ~0.4%, respectively. The authors note that, due to the Eddington bias, sources with a low number of net counts (<~ 10 counts) may have true fluxes lower than those computed using the basic method used here. However, they aim to provide only observed fluxes here and do not make corrections for the Eddington bias.

SB_Flux_Limit
This limit flag for the soft-band flux is set to '<' if the source was not detected in this band, and the quoted value is an upper limit rather than a detection.

SB_Flux
The observed-frame flux of the X-ray source in the standard soft band; quoted fluxes are in units of erg cm-2 s-1. Fluxes have been computed using the sb_counts, and the corresponding exposure time and spectral slope value given in the spectral_index parameter. If sb_flux_limit is '<', then the quoted value is an upper limit rather than a detection. The fluxes have been corrected for absorption by the Galaxy but have not been corrected for material intrinsic to the source. For a power-law model with Gamma = 1.4, the soft-band and hardband Galactic absorption corrections are ~12.6% and ~0.4%, respectively. The authors note that, due to the Eddington bias, sources with a low number of net counts (<~ 10 counts) may have true fluxes lower than those computed using the basic method used here. However, they aim to provide only observed fluxes here and do not make corrections for the Eddington bias.

HB_Flux_Limit
This limit flag for the hard-band flux is set to '<' if the source was not detected in this band, and the quoted value is an upper limit rather than a detection.

HB_Flux
The observed-frame flux of the X-ray source in the standard hard band; quoted fluxes are in units of erg cm-2 s-1. Fluxes have been computed using the hb_counts, and the corresponding exposure time and spectral slope value given in the spectral_index parameter. If hb_flux_limit is '<', then the quoted value is an upper limit rather than a detection. The fluxes have been corrected for absorption by the Galaxy but have not been corrected for material intrinsic to the source. For a power-law model with Gamma = 1.4, the soft-band and hardband Galactic absorption corrections are ~12.6% and ~0.4%, respectively. The authors note that, due to the Eddington bias, sources with a low number of net counts (<~ 10 counts) may have true fluxes lower than those computed using the basic method used here. However, they aim to provide only observed fluxes here and do not make corrections for the Eddington bias.

Notes
This field contains notes on the sources, coded as follows:

      'O' refers to objects that have large cross-band (i.e. between the three
  standard bands) positional offsets (> 2 arcsec); all of these sources lie at
  off-axis angles > 5.5 arcmin.

      'S' refers to close-double or close-triple sources where manual separation
  was required (see discussion in Section 3.2.1 of the reference paper).

      'D' refers to a source having an obvious diffraction spike in the K-band
  image, suggesting the source is likely a Galactic star.

      'LBG' and 'LAE' indicate sources included in the Steidel et al. (2003,
  ApJ, 592, 728) LBG survey and the Hayashino et al. (2004, AJ, 128, 2073) LAE
  survey, respectively.

      'LAB' indicates that the source was coincident with a LAB in the Geach
  et al. (2009, ApJ, 700, 1) study.
  

Contact Person

Questions regarding the SSA22CXO database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 24-May-2012