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CHANDFN1MS - Chandra Deep Field North 1-Megasecond Catalog

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Overview

This table is the Chandra Deep Field North 1-Megasecond Catalog. It lists point sources detected in an extremely deep X-ray survey (1 Ms) of the Hubble Deep Field North (HDF-N) and its environs (~450 square arcminutes) which has been performed with the Advanced CCD Imaging Spectrometer on board the Chandra X-Ray Observatory. This is one of the two deepest X-ray surveys ever performed; for point sources near the aim point, it reaches 0.5 - 2.0 keV and 2 - 8 keV flux limits of ~3 x 10^-17 and ~2 x 10^-16 ergs cm-2 s-1, respectively. 370 distinct point sources have been detected: 360 in the full (0.5 - 8.0 keV) band, 325 in the soft (0.5 - 2.0 keV) band, 265 in the hard (2 - 8 keV) band, and 145 in the ultrahard (4 - 8 keV) band. Source positions are accurate to within 0.6 - 1.7 arcseconds (at ~90% confidence), depending mainly on the off-axis angle. Source densities of 7100 (+1100, -940) deg^-2 (at 4.2 x 10^-17 ergs cm^-2 s^-1) and 4200 (+670, -580) deg^-2 (at 3.8 x 10^-16 ergs cm^-2 s^-1) are observed in the soft and hard bands, respectively.

Catalog Bibcode

2001AJ....122.2810B

References

The Chandra Deep Field North Survey. V. 1 Ms Source Catalogs
         Brandt W.N., Alexander D.M., Hornschemeier A.E., Garmire G.P.,
         Schneider D.P., Barger A.J., Bauer F.E., Broos P.S., Cowie L.L.,
         Townsley L.K., Burrows N., Chartas G., Feigelson D., Griffiths R.E.,
         Nousek J.A., Sargent W.L.W., AJ, 122, 2810. (2001).
         <2001AJ....122.2810B>

Provenance

This online catalog was created by the HEASARC in March 2002 based on a machine-readable version of Table 3 of Brandt et al. (2001) that was obtained from the Astronomical Journal website.

Parameters

Name
The object designation based on the source number (from 1 to 370) given in the original as-published table and the prefix 'BAH 2001' recommended by the Dictionary of Nomenclature of Celestial Objects. The latter notes that an alternative designation for these X-ray sources is 'CXOHDFN JHHMMSS.s+DDMMSS' where HHMMSS.s+DDMMSS are the J2000 equatorial coordinates of the source.

RA
The Right Ascension of the X-ray source in the selected equinox. This was given to a precision of 0.01 seconds of time and in J2000 equatorial coordinates in the original as-published table. These positions have been determined by WAVDETECT when possible. Whenever possible, the position determined in the full band is quoted; when a source is not detected in the full band, there is used, in order of priority, the soft-band position, hard-band position, or ultrahard-band position. In addition, a soft-band position from a no-PSF run is adopted over a full-band position when full-band positional replacement from a no-PSF run was not possible. The priority ordering of position choices above was designed to generally maximize the signal-to-noise ratio of the data being used for positional determination.

Dec
The Declination of the X-ray source in the selected equinox. This was given to a precision of 0.1 arcseconds and in J2000 equatorial coordinates in the original as-published table. These positions have been determined by WAVDETECT when possible. Whenever possible, the position determined in the full band is quoted; when a source is not detected in the full band, there is used, in order of priority, the soft-band position, hard-band position, or ultrahard-band position. In addition, a soft-band position from a no-PSF run is adopted over a full-band position when full-band positional replacement from a no-PSF run was not possible. The priority ordering of position choices above was designed to generally maximize the signal-to-noise ratio of the data being used for positional determination.

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

Error_Radius
The positional error, Delta, in arcseconds. Sources within 5 arcminutes of the average aim point have positional errors of 0.6 arcseconds. Sources farther than 5 arcminutes from the average aim point have positional errors given by the empirically determined equation: Delta [in arcseconds] = 0.6 + (Theta-5')/8.75', where Theta is the off-axis angle in arcminutes. The stated positional errors are for 90% confidence,.

Limit_FB_Counts
A limit flag for the full band counts.

FB_Counts
The full band (FB) counts. All values are for the standard ASCA grade set, and they have not been corrected for vignetting. Source counts and 1-sigma statistical errors have been calculated using circular aperture photometry. The circular aperture was centered at the ra and dec position given in this table. A source-free local background has been subtracted, and unexposed regions were masked. (See the published paper for more details). When a source is not detected in a given band, an upper limit is calculated. All upper limits are determined using circular apertures as above. When the number of counts in the aperture is <=10, the upper limit is calculated using the Bayesian method of Kraft, Burrows, & Nousek (1991) for 95% confidence. For larger numbers of counts in the aperture, upper limits are calculated at the 3-sigma level for Gaussian statistics.

FB_Counts_Error
The 1-sigma statistical error in the full band counts.

FB_Counts_Flag
This parameter contains a flag for the full band counts with the following possible non-blank values:

      a = Source was detected with the restricted ACIS grade set with a
          probability threshold of 10^-7.
      b = Source was detected with the standard ASCA grade set with a
          probability threshold of 10^-5.
      c = Source positional offset >2.5" from the primary source position.
  

Limit_SB_Counts
A limit flag for the soft band counts.

SB_Counts
The soft band (SB) counts. All values are for the standard ASCA grade set, and they have not been corrected for vignetting. Source counts and 1-sigma statistical errors have been calculated using circular aperture photometry. The circular aperture was centered at the ra and dec position given in this table. A source-free local background has been subtracted, and unexposed regions were masked. (See the published paper for more details). When a source is not detected in a given band, an upper limit is calculated. All upper limits are determined using circular apertures as above. When the number of counts in the aperture is <=10, the upper limit is calculated using the Bayesian method of Kraft, Burrows, & Nousek (1991) for 95% confidence. For larger numbers of counts in the aperture, upper limits are calculated at the 3-sigma level for Gaussian statistics.

SB_Counts_Error
The 1-sigma statistical error in the soft band counts.

SB_Counts_Flag
This parameter contains a flag for the soft band counts with the following possible non-blank values:

      a = Source was detected with the restricted ACIS grade set with a
          probability threshold of 10^-7.
      b = Source was detected with the standard ASCA grade set with a
          probability threshold of 10^-5.
      c = Source positional offset >2.5" from the primary source position.
  

Limit_HB_Counts
A limit flag for the hard band counts.

HB_Counts
The hard band (HB) counts. All values are for the standard ASCA grade set, and they have not been corrected for vignetting. Source counts and 1-sigma statistical errors have been calculated using circular aperture photometry. The circular aperture was centered at the ra and dec position given in this table. A source-free local background has been subtracted, and unexposed regions were masked. (See the published paper for more details). When a source is not detected in a given band, an upper limit is calculated. All upper limits are determined using circular apertures as above. When the number of counts in the aperture is <=10, the upper limit is calculated using the Bayesian method of Kraft, Burrows, & Nousek (1991) for 95% confidence. For larger numbers of counts in the aperture, upper limits are calculated at the 3-sigma level for Gaussian statistics.

HB_Counts_Error
The 1-sigma statistical error in the hard band counts.

HB_Counts_Flag
This parameter contains a flag for the hard band counts with the following possible non-blank values:

      a = Source was detected with the restricted ACIS grade set with a
          probability threshold of 10^-7.
      b = Source was detected with the standard ASCA grade set with a
          probability threshold of 10^-5.
      c = Source positional offset >2.5" from the primary source position.
  

Limit_UHB_Counts
A limit flag for the ultrahard band counts.

UHB_Counts
The ultrahard band (UHB) counts. All values are for the standard ASCA grade set, and they have not been corrected for vignetting. Source counts and 1-sigma statistical errors have been calculated using circular aperture photometry. The circular aperture was centered at the ra and dec position given in this table. A source-free local background has been subtracted, and unexposed regions were masked. (See the published paper for more details). When a source is not detected in a given band, an upper limit is calculated. All upper limits are determined using circular apertures as above. When the number of counts in the aperture is <=10, the upper limit is calculated using the Bayesian method of Kraft, Burrows, & Nousek (1991) for 95% confidence. For larger numbers of counts in the aperture, upper limits are calculated at the 3-sigma level for Gaussian statistics.

UHB_Counts_Error
The 1-sigma statistical error in the ultrahard band counts.

UHB_Counts_Flag
This parameter contains a flag for the ultrahard band counts with the following possible non-blank values:

      a = Source was detected with the restricted ACIS grade set with a
          probability threshold of 10^-7.
      b = Source was detected with the standard ASCA grade set with a
          probability threshold of 10^-5.
      c = Source positional offset >2.5" from the primary source position.
  

Limit_Band_Ratio
A limit flag for the band ratio, defined as the ratio of counts between the hard and soft bands.

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.

Band_Ratio_Poserr
The positive error in the band ratio. Errors for this quantity are calculated following the "numerical method" described in Section 1.7.3 of Lyons (1991); 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.

Band_Ratio_Negerr
The negative error in the band ratio. Errors for this quantity are calculated following the "numerical method" described in Section 1.7.3 of Lyons (1991); 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.

Limit_Photon_Index
A limit flag for the effective photon index.

Photon_Index
The effective photon index Gamma for a power-law model with the Galactic column density. This has been calculated based on the band ratio whenever the number of counts is not "low." A source with a low number of counts is defined as being (1) detected in the soft band with less than 30 counts and not detected in the hard band, (2) detected in the hard band with less than 15 counts and not detected in the soft band, (3) detected in both the soft and hard bands, but with less than 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 set to 1.4, a representative value for faint sources that should give reasonable fluxes.

Photon_Index_Flag
This parameter is a flag that is set to 'd' to indicate that the photon index for a particular source is poorly constrained and has been set to 1.4, a representative value for faint sources that should give reasonable fluxes.

Exposure
The effective exposure time derived from the full-band exposure map, in seconds (s). This parameter was given with a precision of 0.1 kiloseconds in the original, as-published table.

Limit_FB_Flux
A limit flag for the full band flux.

FB_Flux
The observed-frame flux in the full band, in units of ergs cm^-2 s^-1, computed using the tabulated full-band counts, the appropriate exposure maps, and the tabulated spectral slope (photon index). The fluxes have been corrected for vignetting but are not corrected for absorption by the Galaxy or intrinsic to the source. For a power-law model with photon index of 1.4, the soft-band and hard-band Galactic absorption corrections are ~4.2% and ~0.1%, respectively.

Limit_SB_Flux
A limit flag for the soft band flux.

SB_Flux
The observed-frame flux in the soft band, in units of ergs cm^-2 s^-1, computed using the tabulated soft-band counts, the appropriate exposure maps, and the tabulated spectral slope (photon index). The fluxes have been corrected for vignetting but are not corrected for absorption by the Galaxy or intrinsic to the source. For a power-law model with photon index of 1.4, the soft-band and hard-band Galactic absorption corrections are ~4.2% and ~0.1%, respectively.

Limit_HB_Flux
A limit flag for the hard band flux.

HB_Flux
The observed-frame flux in the hard band, in units of ergs cm^-2 s^-1, computed using the tabulated hard-band counts, the appropriate exposure maps, and the tabulated spectral slope (photon index). The fluxes have been corrected for vignetting but are not corrected for absorption by the Galaxy or intrinsic to the source. For a power-law model with photon index of 1.4, the soft-band and hard-band Galactic absorption corrections are ~4.2% and ~0.1%, respectively.

Limit_UHB_Flux
A limit flag for the ultrahard band flux.

UHB_Flux
The observed-frame flux in the ultrahard band, in units of ergs cm^-2 s^-1, computed using the tabulated ultrahard-band counts, the appropriate exposure maps, and the tabulated spectral slope (photon index). The fluxes have been corrected for vignetting but are not corrected for absorption by the Galaxy or intrinsic to the source. For a power-law model with photon index of 1.4, the soft-band and hard-band Galactic absorption corrections are ~4.2% and ~0.1%, respectively.

Source_Notes
This parameter contains in some cases source notes according to the following key:

      H = Object lying in the Hubble Deep Field-North (HDF-N) area;
      C = Object lying in the Caltech area;
      O = Object that has large cross-band positional offsets ( >2.5'');
      NP = Object where the source position could not be updated to that from
           a no-PSF run;
      M = Source where the photometry was performed manually;
      S = Close double source where manual separation was required.
  

Contact Person

Questions regarding the CHANDFN1MS database table can be addressed to the HEASARC User Hotline.

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