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CHANDFS1MS - Chandra Deep Field South 1-Megasecond Catalog

HEASARC
Archive

Overview

The Chandra Deep Field South (CDFS) 1-Megasecond Catalog is the source catalog obtained from a 942 kilosecond exposure, using the Advanced CCD Imaging Spectrometer (ACIS-I) on the Chandra X-ray Observatory. Eleven individual pointings made between 1999 October and 2000 December were combined to generate the final image used for object detection. Catalog generation proceeded simultaneously using two different methods: a method of the authors' own design using a modified version of the SExtractor algorithm, and a wavelet transform technique developed specifically for Chandra observations. The detection threshold was set in order to have less than 10 spurious sources, as assessed by extensive simulations. The catalog as published was subdivided into four sections: the primary list consisting of objects common to the two detection methods, two secondary lists containing sources which were detected by either the SExtractor algorithm alone or by the wavelet technique alone, and the fourth list consisting of possible diffuse or extended sources. The flux limits at the aimpoint for the soft (0.5 - 2 keV) and hard (2 - 10 keV) bands are 5.5 x 10^-17 erg/s/cm^2 and 4.5 x 10^-16 erg/s/cm^2, respectively. The total number of sources is 346; out of them, 307 were detected in the 0.5 - 2 keV band, and 251 in the 2 - 10 keV band.

Optical identifications are also presented for the catalogued sources. The primary optical data are R band imaging from VLT/FORS1 to a depth of R ~ 26.5 (Vega). In regions of the field not covered by the VLT/FORS1 deep imaging, the authors use R-band data obtained with the Wide Field Imager (WFI) on the ESO-MPI 2.2 m telescope, as part of the ESO Imaging Survey (EIS), which cover the entire X-ray survey. The FORS1/Chandra offsets are small, ~1 arcsecond. Coordinate cross-correlation finds 85% of the Chandra sources covered by FORS1 R to have counterparts within the 3-sigma error box (>~1.5 arcseconds, depending on off-axis angle and X-ray signal-to-noise). The unidentified fraction of sources, approximately 10% - 15%, is close to the limit expected from the observed X-ray flux to R-band ratio distribution for the identified sample.


Catalog Bibcode

2002ApJS..139..369G

References

Chandra Deep Field South: the 1 Ms catalog.
    Giacconi R., Zirm A., Wang J., Rosati P., Nonino M., Tozzi P., Gilli R.,
    Mainieri V., Hasinger G., Kewley L., Bergeron J., Borgani S., Gilmozzi R.,
    Grogin N., Koekemoer A., Schreier E., Zheng W., Norman C.
   <Astrophys. J. Suppl. Ser. 139, 369 (2002)>
   =2002ApJS..139..369G

Provenance

This online catalog was created by the HEASARC in June 2002 based on machine-readable versions of 2, 3 and 4 of Giacconi et al. (2002) that were obtained from the CDS.

HEASARC Implementation

This HEASARC table contains only the objects in the first three sections of the published catalog (the data listed in Tables 2, 3, and 4 to be precise). We have added a new parameter called 'detect_method' to indicate which original table any given entry comes from: (a) objects from Table 2 of the published catalog which were common to both detection methods have detect_method = 'both', (b) objects from Table 3 which were detected by the SExtractor algorithm alone have detect_method = 'sextractor', and (c) objects from Table 4 which were detected by the wavelet technique alone have detect_method = 'wavdetect'. This HEASARC table does not include the following 19 diffuse or extended sources which were listed in Table 5 of the published catalog:

Xray_ID    RA  (J2000)  Dec      SB_Counts   SB_Flux   SB_SNR   FWHM    OAA
         h  m  s      d  '  "       cts     erg/s/cm^2         arcsec  arcmin

 37      3 32 32.21 -27 41 56.22    89.8     5.03E-16    8.0     5.6    6.77
116      3 32 30.07 -27 44  5.35    93.0     5.29E-16    8.8     3.9    4.58
132      3 32 44.09 -27 54 56.12    40.9     2.19E-16    4.8     6.9    7.17
138      3 32 50.11 -27 41 35.30    51.8     9.13E-16    5.9     7.3    8.54
147      3 32 46.43 -27 46 32.74    25.9     1.49E-16    4.0     4.1    4.50
240      3 32 59.20 -27 51 40.43    43.8     2.46E-16    4.9     7.4    7.43
249      3 32 19.49 -27 54  6.55    27.4     1.46E-16    3.7     8.2    5.80
507      3 33  0.12 -27 49 25.50    23.3     1.43E-16    3.0     5.7    7.04
511      3 32 36.63 -27 46 31.30    22.6     1.27E-16    3.5     5.8    2.79
514      3 32 33.56 -27 43 12.40    27.1     1.57E-16    4.1     5.0    5.56
522      3 32 21.50 -27 55 50.99    68.2     3.78E-16    6.6     6.1    7.36
527      3 32 18.59 -27 54 14.40    36.6     1.97E-16    4.4     6.6    6.00
529      3 32 16.32 -27 55 25.97    23.4     1.32E-16    3.0     9.0    7.29
544      3 31 54.64 -27 51  4.75    34.7     1.90E-16    3.9     6.5    7.86
560      3 32  6.27 -27 45 38.02    23.2     1.26E-16    3.6     5.5    5.77
566      3 32 18.11 -27 47 19.50    30.9     2.33E-16    4.5     3.4    2.65
581      3 32  7.47 -27 49 43.68    17.6     9.51E-17    3.0     3.8    4.77
594      3 32  9.83 -27 42 49.68   237.0     1.36E-15    12.0    8.1    7.14
645      3 32 49.95 -27 49 41.74   262.1     1.75E-15     9.0    ...    8.58
(most parameters above are the same as in the HEASARC table, except for SB_SNR, the signal-to-noise of the source in the soft band, and OAA, the off-axis angle of the source in arcminutes):

Parameters

Optical_ID
The optical cut-out identification number, in order of increasing RA. This parameter is unique only within the separate subsets of sources which were detected by one of the three possible ways: (a) objects that were common to the two alternative detection methods (these have detect_method = 'both' in this HEASARC table), (b) objects which were detected by the SExtractor algorithm alone (detect_method = 'sextractor'), or (c) objects which were detected by the wavelet technique alone (detect_method = 'wavdetect').

The optical cut-out identification number has been used by Simbad to create one of the alternate names for sources in this catalog, namely '[GZW2002] Main NNN' for objects common to both detection methods and that were listed in the main table (Table 2) of the published catalog, '[GZW2002] SExtractor NNN' for objects detected by the SExtractor algorithm alone, and '[GZW2002] WAVDETECT NNN' for objects detected by the wavelet technique alone, where NNN is the value of optical_id.

Xray_ID
A unique X-ray detection identification running number. This number has been used by Simbad to create one of the alternate names for sources in this catalog, namely '[GZW2002] XID NNN', where NNN is the value of xray_id for a given source.

Name
The IAU-registered name for the X-ray source, based on the original (not offset) J2000 equatorial coordinates of the X-ray source.

RA
The Right Ascension of the Chandra X-ray source, in the selected equinox. This value includes an offset of -1.1 arcseconds from the original Chandra position which was calculated based on a cross-correlation versus the FORS1 R-band image. The RA was given in J2000 coordinates and with a precision of 0.01 seconds of time in the original published tables.

Dec
The Declination of the Chandra X-ray source, in the selected equinox. This value includes an offset of +0.8 arcseconds from the original Chandra position which was calculated based on a cross-correlation versus the FORS1 R-band image. The Declination was given in J2000 coordinates and with a precision of 0.01 arcseconds in the original published tables.

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

BII
The Galactic Latitude where of the Chandra X-ray source.

SB_Counts
The net counts in the soft (0.5 - 2 keV) band.

SB_Counts_Error
The uncertainty in the net soft band counts.

HB_Counts
The net counts in the hard (2 - 10 keV) band.

HB_Counts_Error
The uncertainty in the net hard band counts.

SB_Exposure
The effective exposure time in the soft band, in seconds. This parameter was given with a precision of 0.1 kiloseconds in the original, as-published table.

HB_Exposure
The effective exposure time in the hard band, in seconds. This parameter was given with a precision of 0.1 kiloseconds in the original, as-published table.

Limit_SB_Flux
An upper limit flag for the soft band flux.

SB_Flux
The flux in the soft (0.5 - 2 keV) band, in erg/cm^2/s, calculated from the net count rate in the soft band (obtained by dividing the net soft band counts by the effective exposure time, which includes the effect of vignetting) and using the conversion factor given below; notice that the quoted flux has been increased by 4% compared to the original value in order to account for photometric bias. To derive the energy flux from the observed count rate, the authors assumed a conversion factor appropriate for the measured average spectrum of all the sources, Gamma = 1.375 +/- 0.015 (found for all the 1 Ms sources). After fixing the local absorption to the Galactic value of 8 x 10^19 cm^-2, the authors derived a conversion factor of (4.6 +/- 0.1) x 10^-12 erg cm^-2 ct^-1 from count rate to flux in ergs s^-1 cm^-2 in the soft band. The uncertainties correspond to Gamma = 1.4 +/- 0.3. With the adopted conversion factor, the minimum flux achieved in the soft band is 5.5 x 10^-17 erg s^-1 cm^-2.

SB_Flux_Error
The uncertainty in the soft band flux, in erg/cm^2/s; this includes only the Poissonian error resulting from the source and background counts.

Limit_HB_Flux
An upper limit flag for the hard band flux.

HB_Flux
The flux in the hard (2 - 10 keV) band, in erg/cm^2/s, calculated from the net count rate in the hard band (obtained by dividing the net hard band counts by the effective exposure time, which includes the effect of vignetting) and using the conversion factor given below; notice that the quoted flux has been increased by 4% compared to the original value in order to account for photometric bias. To derive the energy flux from the observed count rate, the authors assumed a conversion factor appropriate for the measured average spectrum of all the sources, Gamma = 1.375 +/- 0.015 (found for all the 1 Ms sources). After fixing the local absorption to the Galactic value of 8 x 10^19 cm^-2, the authors derived a conversion factor of (3.0 +/- 0.3) x 10^-11 erg cm^-2 ct^-1 from count rate to flux in ergs s^-1 cm^-2 in the hard band. The uncertainties correspond to Gamma = 1.4 +/- 0.3. With the adopted conversion factor, the minimum flux achieved in the hard band is 4.5 x 10^-16 erg s^-1 cm^-2.

HB_Flux_Error
The uncertainty in the hard band flux, in erg/cm^2/s; this includes only the Poissonian error resulting from the source and background counts.

Hardness_Ratio
The hardness ratio of the X-ray source, defined as HR = (H-S)/(H+S) where H and S are the net counts in the hard and soft bands, respectively.

Hardness_Ratio_Error
The uncertainty in the hardness ratio.

Error_Radius
The error in the X-ray source position, in arcseconds, calculated as described in the text of the published paper.

Offset_1
Separation of X-ray source from nearest candidate optical counterpart, in arcseconds.

Limit_Rmag_1
Limit flag for R magnitude of the nearest candidate optical counterpart.

Rmag_1
Vega R magnitude of the nearest candidate optical counterpart.

Rmag_1_Error
Uncertainty in the Vega R magnitude of the nearest candidate optical counterpart.

Filter_Rmag_1
Code for the filter for the Rmag observation of the nearest optical counterpart, where F stands for the FORS filter and W for the WFI filter.

Offset_2
Separation of X-ray source from second nearest candidate optical counterpart, in arcseconds.

Limit_Rmag_2
Limit flag for R magnitude of the second nearest candidate optical counterpart.

Rmag_2
Vega R magnitude of the second nearest candidate optical counterpart, if there is one.

Rmag_2_Error
Uncertainty in the Vega R magnitude of the second nearest candidate optical counterpart.

Filter_Rmag_2
Code for the filter for the Rmag observation of the second nearest optical counterpart, where F stands for the FORS filter and W for the WFI filter.

Offset_3
Separation of X-ray source from third nearest candidate optical counterpart, in arcseconds.

Limit_Rmag_3
Limit flag for R magnitude of the third nearest candidate optical counterpart.

Rmag_3
Vega R magnitude of the third nearest candidate optical counterpart, if there is one.

Rmag_3_Error
Uncertainty in the Vega R magnitude of the third nearest candidate optical counterpart.

Filter_Rmag_3
Code for the filter for the Rmag observation of the third nearest optical counterpart, where F stands for the FORS filter and W for the WFI filter.

Detect_Method
This parameter was created by the HEASARC to indicate which original table from the published version of the catalog any given entry comes from: (a) objects from Table 2 of the published catalog which were common to both detection methods have detect_method = 'both', (b) objects from Table 3 which were detected by the SExtractor algorithm alone have detect_method = 'sextractor', and (c) objects from Table 4 which were detected by the wavelet technique alone have detect_method = 'wavdetect'.


Contact Person

Questions regarding the CHANDFS1MS database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 8-Aug-2006