CHANDFS2MS - Chandra Deep Field South 2-Megasecond Catalog

Overview

This table contains point-source catalogs for the ~2 Ms exposure of the Chandra Deep Field-South (CDF-S) this is one of the two most sensitive X-ray surveys ever performed. The survey covers an area of ~436 arcmin² and reaches on-axis sensitivity limits of ~1.9 x 10^-17 and ~1.3 x 10^-16 erg cm^-2 s^-1 for the 0.5-2.0 and 2-8 keV bands, respectively. Four hundred and sixty-two X-ray point sources (source_sample = 'Main CDF-S' in this table) are detected in at least one of three X-ray bands that were searched; 135 of these sources are new compared to the previous ~1 Ms CDF-S detections. Source positions are determined using centroid and matched-filter techniques; the median positional uncertainty is ~0.36". The X-ray-to-optical flux ratios of the newly detected sources indicate a variety of source types; ~55% of them appear to be active galactic nuclei, while ~45% appear to be starburst and normal galaxies. This table contains, in addition to the main Chandra catalog, the supplementary catalog of 86 X-ray sources (source_sample = 'CDF-S + E-CDF-S' in this table) in the ~2 Ms CDF-S footprint that was created by merging the ~250 ks Extended Chandra Deep Field-South with the CDF-S; this approach provides additional sensitivity in the outer portions of the CDF-S. This table also contains a second supplementary catalog (source_sample = 'Optically Bright' in this table) of 30 X-ray sources which was constructed by matching lower significance X-ray sources to bright optical counterparts (R < 23.8); the majority of these sources appear to be starburst and normal galaxies. The total number of sources in this table, which contains the main and 2 supplementary catalogs, is thus 578. Optical R-band counterparts and basic optical and infrared photometry are provided for the X-ray sources in the main and supplementary catalogs. The authors also include existing spectroscopic redshifts for 224 of the X-ray sources. The average backgrounds in the 0.5-2.0 and 2-8 keV bands are 0.066 and 0.167 counts Ms^-1 pixel^-1, respectively, and the background counts follow Poisson distributions. The effective exposure times and sensitivity limits of the CDF-S are now comparable to those of the ~2 Ms Chandra Deep Field-North (CDF-N). In their paper, the authors also present cumulative number counts for the main catalog and compare the results to those for the CDF-N. The soft-band number counts for these two fields agree well with each other at fluxes higher than ~2 x 10^-16 erg cm^-2 s^-1, while the CDF-S number counts are up to ~25% smaller than those for the CDF-N at fluxes below ~2 x 10^-16 erg cm^-2 s^-1 in the soft band and ~2 x 10^-15 erg cm^-2 s^-1 in the hard band, suggesting small field-to-field variations.

Catalog Bibcode

2008ApJS..179...19L

References

The Chandra Deep Field-South Survey: 2-Megasecond Source Catalog
    Luo B., Bauer F.E., Brandt W.N., Alexander D.M., Lehmer B.D.
    Schneider D.P., Brusa M., Comastri A., Fabian A.C., Finoguenov A.,
    Gilli R., Hasinger G., Hornschemeier A.E., Koekemoer A., Mainieri V.,
    Paolillo M., Rosati P., Shemmer O., Silverman J.D., Smail I.,
    Steffen A.T., Vignali C.
   <Astrophys. J. Suppl., 179, 19-36 (2008)>
   =2008ApJS..179...19L

Provenance

This table was created by the HEASARC in December 2008 based on the electronic version of Tables 2, 5 and 6 from the reference paper which were obtained from the ApJ web site. It was last modified by the HEASARC in July 2011.

Revisions Made in 2011

This table was modified slightly in July 2011 as follows:

(1) Sources from the second supplementary catalog (source_sample = 'Optically Bright') were given alternative names with the prefix of '[LBB2008] SO' rather than the '[LBB2008] SO+' used in the original December 2008 version of this table;

(2) A new parameter source_identifier was added to better enable linking of the entries in this table to those in the Chandra Deep Field South 4-Megasecond Catalog (the HEASARC Browse CHANDFS4MS table) by adopting the source number naming convention used for 2-MS sources in the latter catalog, namely:

(a) Sources from the Main Chandra Catalog (source_sample = 'Main CDF-S') have been given source_identifier values of the form '1' to '462', where these numbers are the source numbers listed in Table 2 of the reference paper in order of increasing J2000.0 Right Ascension within the given table;

(b) Sources from the Supplementary CDF-S Plus E-CDF-S Chandra Catalog (source_sample = 'CDF-S + E-CDF-S') have been given source_identifier values of the form 'SP1_1' to 'SP1_86', where these numbers are the source numbers listed in Table 5 of the reference paper in order of increasing J2000.0 Right Ascension within the given table;

(c) Sources from the Supplementary Optically Bright Chandra Catalog (source_sample = 'Optically Bright') have been given source_identifier values of the form 'SP2_1' to 'SP2_30', where these numbers are the source numbers listed in Table 6 of the reference paper in order of increasing J2000.0 Right Ascension within the given table.

Parameters

Alt_Name
An alternative source designation, based on the '[LBB2008]' prefix (for Luo, Bauer, Brandt 2008), a source sample identifier, and a source number, as recommended by the CDS Dictionary of Nomenclature of Celestial Objects. Objects from Table 2 of the reference paper (source_sample = 'Main CDF-S') have names such as '[LBB2008] 1', objects from Table 5 of the reference paper (source_sample= 'CDF-S + E-CDF-S') have names such as '[LBB2008] S1', and objects from Table 6 of the reference paper (source_sample = 'Optically Bright') have names such as '[LBB2008] SO1'.

RA
The Right Ascension of the X-ray source in the selected equinox. These positions have been determined following the procedure described in Section 3.3 of the reference paper. To avoid truncation error, the positions are given to a higher precision (0.01 seconds of time in J2000.0 coordinates in the original table) than in the International Astronomical Union (IAU)-registered source names. The wavdetect positions are used for the faint X-ray sources in the supplementary optically bright sample. Whenever possible, the authors have quoted the position determined in the full band; when a source was not detected in the full band, they used, in order of priority, the soft-band position or the hard-band position.

Dec
The Declination of the X-ray source in the selected equinox. These positions have been determined following the procedure described in Section 3.3 of the reference paper. To avoid truncation error, the positions are given to higher precision (0.1 arcseconds in J2000.0 coordinates in the original table) than in the International Astronomical Union (IAU)-registered source names. The wavdetect positions are used for the faint X-ray sources in the supplementary optically bright sample. Whenever possible, the authors have quoted the position determined in the full band; when a source was not detected in the full band, they used, in order of priority, the soft-band position or the hard-band position.

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

Name
The position-based IAU source designation, using the 'CXOCDFS' prefix and the J2000.0 equatorial source coordinates, e.g., 'CXOCDFS J033134.1-275004'.

Error_Radius
The ~85% confidence-level positional uncertainty, in arcseconds. As shown in Section 3 of the reference paper, the positional uncertainty depends on the off-axis angle and the number of detected counts, and is estimated following equation (1) therein. The minimum positional uncertainty is ~0.23 arcsec for sources in the main catalog, and the maximum value is ~1.90 arcsec. For the faint X-ray sources in the supplementary optically bright sample, the positional uncertainty is set to 1.2 arcsec, the approximate 90th percentile of the optical-X-ray positional offsets of these sources.

Off_Axis
The off-axis angle of the X-ray source, in arcminutes. This is calculated using the X-ray source position and the average aim point of the CDF-S (see Table 1 of the reference paper).

FB_Counts
The full-band (0.5-8.0 keV) source counts or the upper limits on the source counts. The entries have not been corrected for vignetting. Source counts and statistical errors have been calculated using circular-aperture photometry; extensive testing has shown that this method is more reliable than the wavdetect photometry (e.g., Brandt et al. 2001, AJ, 122, 1; Alexander et al. 2003, AJ, 126, 539 = A03). The circular aperture was centered at the position given by the ra and dec parameters for all bands. The authors have also computed photometry using the reduction tool acis_extract (AE), and the results are in good agreement with this circular-aperture photometry. The local background is determined in an annulus outside of the source-extraction region. The mean number of background counts per pixel is calculated from a Poisson model using n₁/n₀, where n₀ is the number of pixels with 0 counts and n₁ is the number of pixels with 1 count (e.g., A03). By ignoring all pixels with more than 1 count, this technique is robust against background contamination from sources. See Section 3.3 of the reference paper for more details of the background subtraction procedure.

For sources with fewer than 1000 full-band counts, the authors have chosen the aperture radii based on the encircled-energy function of the Chandra PSF as determined using the CXC's MKPSF software. In the soft band, where the background is lowest, the aperture radius was set to the 95% encircled-energy radius of the PSF. In the full and hard bands, the 90% encircled-energy radius of the PSF was used. Appropriate aperture corrections were applied to the source counts by dividing the extracted source counts by the encircled-energy fraction for which the counts were extracted. For sources with more than 1000 full-band counts, systematic errors in the aperture corrections often exceed the expected errors from photon statistics when the above apertures are used. Therefore, for such high count-rate sources, the authors used larger apertures to minimize the importance of the aperture corrections; this is appropriate since these bright sources dominate over the background. They set the aperture radii to be twice the 90% encircled-energy full-band radii and inspected these sources to verify that the measurements were not contaminated by neighboring objects. No aperture corrections were applied to these sources. Manual correction of the source photometry was performed for sources having overlapping PSFs. For sources in the supplementary optically bright sample, when a source is detected in a given band, the photometry is taken directly from wavdetect.

When a source is not detected in a given band, an upper limit is calculated; upper limits are indicated as a in the associated error parameters. All upper limits are determined using the circular apertures described above. When the number of counts in the aperture is <= 10, the upper limit is calculated using the Bayesian method of Kraft et al. (1991, ApJ, 374, 344) for 99% confidence. The uniform prior used by these authors results in fairly conservative upper limits, and other reasonable choices of priors do not materially change the scientific results. For larger numbers of counts in the aperture, upper limits are calculated at the 3-sigma level for Gaussian statistics.

FB_Counts_Pos_Err
The 1-sigma upper statistical error (Gehrels 1986, ApJ, 303, 336) corresponding to the quoted counts in this band. When a source is not detected in a given band, an upper limit is calculated instead; upper limits are indicated by the associated error parameters having null values.

FB_Counts_Neg_Err
The 1-sigma lower statistical error (Gehrels 1986, ApJ, 303, 336) corresponding to the quoted counts in this band. When a source is not detected in a given band, an upper limit is calculated instead; upper limits are indicated by the associated error parameters having null values.

SB_Counts
The soft-band (0.5-2.0 keV) source counts or the upper limits on the source counts. See the fb_counts parameter description for further details.

SB_Counts_Pos_Err
The 1-sigma upper statistical error (Gehrels 1986, ApJ, 303, 336) corresponding to the quoted counts in this band. When a source is not detected in a given band, an upper limit is calculated instead; upper limits are indicated by the associated error parameters having null values.

SB_Counts_Neg_Err
The 1-sigma lower statistical error (Gehrels 1986, ApJ, 303, 336) corresponding to the quoted counts in this band. When a source is not detected in a given band, an upper limit is calculated instead; upper limits are indicated by the associated error parameters having null values.

HB_Counts
The hard-band (2.0-8.0 keV) source counts or the upper limits on the source counts. See the fb_counts parameter description for further details.

HB_Counts_Pos_Err
The 1-sigma upper statistical error (Gehrels 1986, ApJ, 303, 336) corresponding to the quoted counts in this band. When a source is not detected in a given band, an upper limit is calculated instead; upper limits are indicated by the associated error parameters having null values.

HB_Counts_Neg_Err
The 1-sigma lower statistical error (Gehrels 1986, ApJ, 303, 336) corresponding to the quoted counts in this band. When a source is not detected in a given band, an upper limit is calculated instead; upper limits are indicated by the associated error parameters having null values.

Optical_RA
The right ascension of the optical counterpart to the X-ray 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.

The optical counterpart positions were obtained by matching the X-ray source positions to WFI R-band source positions using a matching radius that is 1.5 times the quadratic sum of the positional errors of the X-ray and optical sources. This matching radius was chosen to provide a large number of optical counterparts without introducing too many false matches. The WFI R-band observations have a 5-sigma limiting AB magnitude of 27.3 over the entire CDF-S field. For four sources (our sources 74, 283, 328, and 431) that have more than one optical match, the magnitude difference between the counterparts is less than 3 in all cases, and therefore the source with the smallest offset was selected as the most probable counterpart. Using these criteria, 344 (~74%) of the sources in the main catalog (entries with source_sample = 'Main CDF-S') have optical counterparts. Sources with no optical counterparts have blank right ascension and declination values.

Optical_Dec
The declination of the optical counterpart to the X-ray source in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.1 arcseconds in the original table.

Offset
The measured offset between the optical and X-ray source positions, in arcseconds. Sources with no optical counterparts have blank values. The offsets for all matches are below 2.0 arcsec.

Rmag
The R-band AB magnitude (WFI) of the optical counterpart to the X-ray source. Sources with no optical counterparts have blank values.

Goodss_Source_Number
The corresponding source number from the Great Observatories Origins Deep Survey-South (GOODS-S) version 2.0 i-band source catalog. The authors matched the positions of the optical counterparts (ra_optical and dec_optical) to the GOODS-S source positions using a matching radius of 0.5 arcsec. In 6 cases (sources 88, 120, 135, 155, 313, and 322) where there is more than one GOODS-S source matching to an optical counterpart, the authors selected the GOODS-S source with the smallest offset as the most probable match. For the 344 optical counterparts to X-ray sources in the main catalog (entries with source_sample = 'Main CDF-S'), 218 matches were found; note that the GOOD-S field does not cover the whole CDF-S. By shifting the coordinates of the optical counterparts and re-correlating with the GOODS-S sources, the authors estimated the false-match probability to be <=5%. Sources with no GOODS-S match have blank values.

Imag
The i-band AB magnitude (GOODS-S) from the Great Observatories Origins Deep Survey-South (GOODS-S) version 2.0 i-band source catalog. The GOODS-S i-band observations have a 5-sigma limiting AB magnitude of 28.5. The i-band magnitude is the SExtractor corrected isophotal magnitude. Sources with no GOODS-S match have blank values.

Gems_Name
The corresponding coordinate-based source name of the optical counterpart from the Galaxy Evolution from Morphologies and SEDs (GEMS) source catalog. The authors matched the positions of the optical counterparts (see the optical_ra and optical_dec parameters) to the GEMS source positions using a matching radius of 0.5 arcsec. In one case (the source with alt_name of '[LBB2008] 74') where there is more than one GEMS source matching to an optical counterpart, the authors selected the GEMS source with the smallest offset as the most probable match. For the 344 optical counterparts to X-ray sources in the main catalog (entries with source_sample = 'Main CDF-S'), 297 matches were found. By shifting the coordinates of the optical counterparts and re-correlating with the GEMS sources, the authors estimated the false-match probability to be <~ 2%. Sources with no GEMS match have blank values.

Zmag
The corresponding z-band AB-magnitude of the optical counterpart from the Galaxy Evolution from Morphologies and SEDs (GEMS) source catalog. The GEMS z-band observations have a 5-sigma limiting AB magnitude of 27.3 over the entire CDF-S field. The z-band magnitude is the SExtractor MAG_BEST magnitude. Sources with no GEMS match have blank values.

SOFI_Source_Number
The corresponding source number from the source catalog for the ESO/New Technology Telescope SOFI survey of the CDF-S region. The authors matched the positions of the optical counterparts (see the optical_ra and optical_dec parameters) to the SOFI source positions using a matching radius of 0.75 arcsec. For the 344 optical counterparts to X-ray sources in the main catalog (entries with source_sample = 'Main CDF-S'), 266 matches were found. By shifting the coordinates of the optical counterparts and re-correlating with the SOFI sources, the authors estimated the false-match probability to be <~ 1%. Sources with no SOFI match have blank values.

Ks_Mag
The corresponding K_s band magnitude of the optical counterpart from the source catalog for the ESO/New Technology Telescope SOFI survey of the CDF-S region. The SOFI K_s-band observations have a 5-sigma limiting AB magnitude of 23.0 over the entire CDF-S field. The K_s-band magnitude is the SExtractor-corrected isophotal magnitude. Sources with no SOFI match have blank values.

IRAC_Source_Number
The corresponding source number of the infrared counterpart from the Spitzer IRAC/MUSYC Public Legacy Survey in the E-CDF-S (SIMPLE) source catalog. The authors matched the positions of the optical counterparts (see the optical_ra and optical_dec parameters) to the SIMPLE source positions using a matching radius of 0.75 arcsec. For the 344 optical counterparts to X-ray sources in the main catalog (entries with source_sample = 'Main CDF-S'), 306 matches were found. By shifting the coordinates of the optical counterparts and re-correlating with the SIMPLE sources, the authors estimated the false-match probability to be <~ 2%. Sources with no SIMPLE match have blank values.

Flux_5p8_um
The IRAC 5.8-micron flux density, in microJanskies (µJy), from the Spitzer IRAC/MUSYC Public Legacy Survey in the E-CDF-S (SIMPLE) source catalog. The SIMPLE 5.8-micron observations have a 5-sigma limiting AB magnitude of 21.9 - 22.5 over the entire CDF-S field; the limiting magnitude is spatially dependent for SIMPLE. The 5.8-micron flux density is the aperture flux density in a 2.0 arcsec circular aperture, normalized to an AB magnitude zero point of 25. Note that an aperture correction of ~ 1.5 was not applied to these fluxes. Sources with no SIMPLE match have blank values.

Redshift
The corresponding spectroscopic redshift of the optical counterpart to the X-ray source. A matching radius of 0.5 arcsec was used when matching the optical counterparts (see the optical_ra and optical_dec parameters) to the redshift catalogs. Of the 344 optical counterparts to X-ray sources in the main catalog (entries with source_sample = 'Main CDF-S'), 190 have redshift measurements. By shifting the coordinates of the optical counterparts and re-correlating with the redshift catalogs, the authors estimated the false-match probability to be <~ 1%. Sources with no secure spectroscopic redshift have these two columns set to blank values. Note that there are also photometric redshifts available in the literature, but these are not included in this catalog.

Ref_Redshift
The corresponding reference codes for the references from which the spectroscopic redshift were obtained. Secure spectroscopic redshifts were collected from Le Fevre et al. (2004, A&A, 428, 1043), Szokoly et al. (2004, ApJS, 155, 271), Mignoli et al. (2005, A&A, 437, 883), Ravikumar et al. (2007, A&A, 465, 1099), Popesso et al. (2008, A&A, submitted), and Vanzella et al. (2008, A&A, 478, 83), and these have been given the reference numbers of 1 - 6, respectively.

L05_Source_Number
For sources in the Extended Chandra Deep Field South (entries with source_sample = 'E-CDF-S'), this is the corresponding ~ 250 ks E-CDF-S source number from the main Chandra catalog presented in Lehmer et al. (2005, ApJS, 161, 21), the L05 Catalog (see col. [1] of Table 2 in L05). The authors matched their X-ray source positions to L05 source positions using a matching radius that is the quadratic sum of the ~ 3-sigma positional errors of the CDF-S and L05 X-ray sources. The 3-sigma positional error of a CDF-S source is approximately twice the positional error quoted in the error_radius parameter, and that of an L05 source is approximately twice the positional error quoted in Table 2 of L05. Only one L05 match was found for each matched source. Sources with no L05 match have a null value.

L05_RA
The Right Ascension of the corresponding L05 source in the selected equinox. Sources with no L05 match have a null value.

L05_Dec
The Declination of the corresponding L05 source in the selected equinox. Sources with no L05 match have a null value.

A03_Source_Number
The corresponding ~ 1 Ms CDF-S source number from the main Chandra catalog presented in Alexander et al. (2003, AJ, 126, 539), the A03 Catalog (see col. [1] of Table A2a in A03). The authors matched their X-ray source positions to A03 source positions using a matching radius that was the quadratic sum of the ~ 3-sigma positional errors of the CDF-S and A03 X-ray sources. The 3-sigma positional error of a CDF-S source is approximately twice the positional error quoted in the error_radius parameter, and that of an A03 source is approximately twice the positional error quoted in Table A2a of A03. The false match probability is less than 1% with this matching radius. Only one A03 match was found for each matched source. In one case where two close-double sources matched to one A03 source, the authors chose the source with the smallest offset (source 433) as the most probable match. They manually set the counterpart of the source with source number 437 to be source 312 in A03, because A03 apparently underestimated the positional error of this source. Sources with no A03 match have a null value.

A03_RA
The Right Ascension of the corresponding A03 source in the selected equinox. Sources with no A03 match have a null value.

A03_Dec
The Declination of the corresponding A03 source in the selected equinox. Sources with no A03 match have a null value.

G02_Source_Number
The corresponding ~ 1 Ms CDF-S source "ID" number from the main Chandra catalog presented in Giacconi et al. (2002, ApJS, 139, 369), the G02 Catalog (available as the CHANDFS1MS table in HEASARC Browse),their Table 2. When matching their CDF-S source positions with G02 counterparts, the authors removed offsets to the G02 positions of ~ 1.2 arcsec in Right Ascension and 0.8 arcsec in declination (see Section A3 of A03); these positions are corrected in the quoted source positions in the g02_ra and g02_dec parameters herein. The authors used a matching radius that is the quadratic sum of the ~ 3-sigma positional errors of the CDF-S and G02 X-ray sources. The 3-sigma positional error of a CDF-S source is approximately twice the positional error quoted in the error_radius parameter, and that of a G02 source is quoted in Table 2 of G02. Only one G02 match was found for each matched source. In three cases where two close-double sources matched to one G02 source, the authors chose the source with the smallest offset (sources 142, 195, and 275) as the most probable match. Sources with no G02 match have a null value for this parameter. Note that there are no matches in the supplementary optically bright sample (source_sample = 'Optically Bright' in this HEASARC table) to the main source catalog in G02, so all such sources have null values for this parameter.

XID_Source_Number
The corresponding ~ 1 Ms CDF-S source "XID" number from the main Chandra catalog presented in Giacconi et al. (2002, ApJS, 139, 369), the G02 Catalog (available as the CHANDFS1MS table in HEASARC Browse),their Table 2. Sources with no G02 match have a null value for this parameter. Note that there are no matches in the supplementary optically bright sample (source_sample = 'Optically Bright' in this HEASARC table) to the main source catalog in G02, so all such sources have null values for this parameter.

G02_RA
The Right Ascension of the corresponding G02 source in the selected equinox. Note that the quoted positions have been corrected by the offsets described above (see Section A3 of A03). Sources with no G02 match have Right Ascension values set to null values.

G02_Dec
The Declination of the corresponding G02 source in the selected equinox. Note that the quoted positions have been corrected by the offsets described above (see Section A3 of A03). Sources with no G02 match have Declination values set to null values.

FB_Exposure
The effective exposure time in the full band determined from the standard-band exposure maps (see Section 3.1 of the reference paper for details on the exposure maps). Dividing the counts for the corresponding band by the corresponding effective exposures provides the vignetting-corrected and quantum-efficiency degradation corrected count rates. Note that for sources detected in the E-CDF-S (entries with note_flags='L'), the source exposure times, band ratios, photon indices, and fluxes were taken from L05 directly.

SB_Exposure
The effective exposure time in the soft band determined from the standard-band exposure maps (see Section 3.1 of the reference paper for details on the exposure maps). Dividing the counts for the corresponding band by the corresponding effective exposures provides the vignetting-corrected and quantum-efficiency degradation corrected count rates. Note that for sources detected in the E-CDF-S (entries with note_flags='L'), the source exposure times, band ratios, photon indices, and fluxes were taken from L05 directly.

HB_Exposure
The effective exposure time in the hard band determined from the standard-band exposure maps (see Section 3.1 of the reference paper for details on the exposure maps). Dividing the counts for the corresponding band by the corresponding effective exposures provides the vignetting-corrected and quantum-efficiency degradation corrected count rates. Note that for sources detected in the E-CDF-S (entries with note_flags='L'), the source exposure times, band ratios, photon indices, and fluxes were taken from L05 directly.

Band_Ratio
The band ratio, 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. Sources detected only in the full band have band ratios and corresponding errors set to null values. Note that for sources detected in the E-CDF-S (entries with note_flags='L'), the source exposure times, band ratios, photon indices, and fluxes were taken from L05 directly.

Band_Ratio_Pos_Err
The upper error in the band ratio. Errors for this quantity are calculated following the "numerical 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. Note that the error distribution is not Gaussian when the number of counts is small. Upper limits are calculated for sources detected in the soft band but not the hard band, and lower limits are calculated for sources detected in the hard band but not the soft band. For these sources, the upper and lower errors are set to the same value as that of the computed band ratio. Sources detected only in the full band have band ratios and corresponding errors set to null values. Note that for sources detected in the E-CDF-S (entries with note_flags='L'), the source exposure times, band ratios, photon indices, and fluxes were taken from L05 directly.

Band_Ratio_Neg_Err
The lower error in the band ratio. Errors for this quantity are calculated following the "numerical 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. Note that the error distribution is not Gaussian when the number of counts is small. Upper limits are calculated for sources detected in the soft band but not the hard band, and lower limits are calculated for sources detected in the hard band but not the soft band. For these sources, the upper and lower errors are set to the same value as that of the computed band ratio. Sources detected only in the full band have band ratios and corresponding errors set to null values. Note that for sources detected in the E-CDF-S (entries with note_flags='L'), the source exposure times, band ratios, photon indices, and fluxes were taken from L05 directly.

Spectral_Index
The effective photon index (Gamma)of the X-ray source, for a power-law model with the Galactic column density given in Section 1 of the reference paper. When the number of source counts is not low, the effective photon index has been calculated based on the band_ratio value using the CXC's Portable, Interactive, Multi-Mission Simulator (PIMMS). A source with a low number of counts is defined as being (1) detected in the soft band with <30 counts and not detected in the hard band, (2) detected in the hard band with <15 counts and not detected in the soft band, (3) detected in both the soft and hard bands, but with <15 counts in each, or (4) detected only in the full band. When the number of counts is low, the photon index is poorly constrained and is set to Gamma = 1.4, a representative value for faint sources that should yield reasonable fluxes. In this case, the upper and lower errors are set to null values. Note that for sources detected in the E-CDF-S (entries with note_flags='L'), the source exposure times, band ratios, photon indices, and fluxes were taken from L05 directly. For sources in the supplementary optically bright sample (entries with source_sample = 'Optically Bright'), the authors used a constant photon index of Gamma = 2.0 since their source-selection technique preferentially selected objects in this sample with flux ratios f(0.5-2.0 keV)/f_R < 0.1, which are observed to have effective photon indices of ~ 2 (e.g., Section 4.1.1 of Bauer et al. (2004, AJ, 128, 2048).

Spectral_Index_Pos_Err
The upper error in the photon index of the X-ray source.

Spectral_Index_Neg_Err
The lower error in the photon index of the X-ray source.

FB_Flux
The observed-frame flux in the full band; quoted fluxes are in units of ergs cm^-2 s^-1. Fluxes have been computed using the corresponding counts, the appropriate exposure times, and the effective photon indices given in the spectral_index parameter. The fluxes have not been corrected for absorption by the Galaxy or material intrinsic to the source. For a power-law model with Gamma =1.4 , the soft-band and hard-band Galactic absorption corrections are ~ 2.1% and ~ 0.1%, respectively. Note that for sources detected in the E-CDF-S (entries with note_flags='L'), the source exposure times, band ratios, photon indices, and fluxes were taken from L05 directly.

SB_Flux
The observed-frame flux in the soft band; quoted fluxes are in units of ergs cm^-2 s^-1. Fluxes have been computed using the corresponding counts, the appropriate exposure times, and the effective photon indices given in the spectral_index parameter. The fluxes have not been corrected for absorption by the Galaxy or material intrinsic to the source. For a power-law model with Gamma =1.4 , the soft-band and hard-band Galactic absorption corrections are ~ 2.1% and ~ 0.1%, respectively. Note that for sources detected in the E-CDF-S (entries with note_flags='L'), the source exposure times, band ratios, photon indices, and fluxes were taken from L05 directly.

HB_Flux
The observed-frame flux in the hard band; quoted fluxes are in units of ergs cm^-2 s^-1. Fluxes have been computed using the corresponding counts, the appropriate exposure times, and the effective photon indices given in the spectral_index parameter. The fluxes have not been corrected for absorption by the Galaxy or material intrinsic to the source. For a power-law model with Gamma =1.4 , the soft-band and hard-band Galactic absorption corrections are ~ 2.1% and ~ 0.1%, respectively. Note that for sources detected in the E-CDF-S (entries with note_flags='L'), the source exposure times, band ratios, photon indices, and fluxes were taken from L05 directly.

Log_Min_FP_Prob
The logarithm of the minimum false-positive probability run with wavdetect in which each source was detected (see Section 3.2 of the reference paper). A lower false-positive probability indicates a more significant source detection. Of the Main CDF-S sources, 398 (~ 86%) and 357 (~ 77%) are detected with false-positive probability thresholds of 1 x 10^-7 and 1 x 10^-8, respectively. This parameter was not provided for sources in the supplementary optically bright sample.

Note_Flags
This parameters contains flags indicating notes on the sources, as follows: 'E' refers to sources at the edge that lie partially outside of the survey area, 'S' refers to close doubles or triples where manual separation was required. 'B' refers to sources with background counts estimated using the background maps (see Section 3.3.1 of the reference paper for more details), and 'L' refers to sources in the supplementary CDF-S Plus E-CDF-S sample that were detected in the ~ 250 ks E-CDF-S (L05) catalog.

Source_Sample
This HEASARC-created parameter indicates from which published table/sample the entry originates: 'Main CDF-S' indicates it comes from Table 2 of the reference paper ('Main Chandra Catalog'), 'CDF-S + E-CDF-S' from Table 5 of the reference paper ('Supplementary CDF-S Plus E-CDF-S Chandra Catalog'), and 'Optically Bright' from Table 6 of the reference paper ('Supplementary Optically Bright Chandra Catalog').

Source_Identifier
This HEASARC-created parameter (based on a convention used in the Chandra 4-Ms Catalog) uniquely identifies each source in the present catalog, as follows:

Contact Person

Questions regarding the CHANDFS2MS database table can be addressed to the HEASARC Help Desk.

Page Author: Browse Software Development Team
Last Modified: Monday, 16-Sep-2024 17:25:42 EDT