Chandra Source Catalog Release 2.0 Preliminary Detections List
This is a work in progress! Be sure to read the caveats prior to using these data! The Spring 2016 CXC Newsletter article provides more information on the state of version 2 of the Chandra Source Catalog .
Contents
Data Access
The March 2017 release of the data is available at:
 preliminary_detlist.fits.gz (53.4 Mb compressed and 124.4 Mb uncompressed)
It contains the results of Maximum Likelihood Estimator (MLE) fits to the candidate source detections. The column definitions and Caveats for this file can be found below. The file contains 362182 detections, with 279549 labelled as SRC_QUALITY = ‘TRUE’ and 82633 (23%) with SRC_QUALITY = ‘MARGINAL’. When split by EXTSRC_CLASS, there are 358382 detections with a value of ‘POINT’, 3183 (0.9%) with ‘EXTENDED’, and 617 (0.2%) with ‘POSSIBLE’. The breakdown by EBAND—the energy band correponding to the measured values—there are 271687 broad band ('b'), 395 ultrasoft ('u'), 26995 soft ('s'), 26524 medium ('m'), 31297 hard ('h'), and 5284 wide (HRC) band ('w') rows; the band definitions are the same as in release 1. There are 354 detections with STREAK_SRC_FLAG = True.
Column Definitions
unix% dmlist preliminary_detlist.fits blocks  Dataset: preliminary_detlist.fits  Block Name Type Dimensions  Block 1: Null Block 2: DETLIST Table 48 cols x 362182 rows
DETLIST HDU: PRELIMINARY DETECTIONS LIST
Column name  Units  Comment  Example  Data type  FITS format  Notes 

DETECT_ID  Stack_id.component  'acisfJ0123456p012345_001.0001'  string  29A  
LIKELIHOOD  Highest source log likelihood  100.0  double  1D  Highest source likelihood  
SRC_QUALITY  Preliminary source quality  'TRUE'  string  8A  Values are 'TRUE' or 'MARGINAL' and are based on comparison of likelihood with draft catalog thresholds.  
EBAND  Energy band of maximum likelihood value  'b'  string  1A  Energy band corresponding to likelihood value; Science energy band designation (i.e., lower case) not detect energy band: one of 'b', 'u', 's', 'm', 'h', or 'w'.  
THETA  arcmin  Highest likelihood src model mean offaxis ang  0.0  double  1D  Corresponds to fitted [x,y] 
STREAK_SRC_FLAG  Is source on a streak?  'F'  logical  1L  
RA  deg  Highest likelihood source model position RA  20.94000  double  1D  
DEC  deg  Highest likelihood source model position Dec  1.39583  double  1D  
ERR_ELLIPSE_RA  deg  95% confidence error ellipse position RA  20.94000  double  1D  95% confidence error ellipse RA in deg; 0.0 <= ERR_ELLIPSE_RA < 360.0 
ERR_ELLIPSE_DEC  deg  95% confidence error ellipse position Dec  1.39583  double  1D  95% confidence error ellipse Dec in deg; 90.0 <= SRC_ERR_ELLIPSE_DEC_B <= +90.0 
ERR_ELLIPSE_R0  arcsec  95% confidence error ellipse semimajor axis  0.35  double  1D  95% confidence error ellipse semimajor axis radius in arcsec 
ERR_ELLIPSE_R1  arcsec  95% confidence error ellipse semiminor axis  0.30  double  1D  95% confidence error ellipse semiminor axis radius in arcsec 
ERR_ELLIPSE_ANG  deg  95% confidence error ellipse smaj axis rotang  60.0  double  1D  95% confidence error ellipse rotation angle of semimajor axis; 0.0 <= ERR_ELLIPSE_ANG < 180.0; 0.0 along SKY +X, 90.0 along SKY +Y 
SRC_RDATA_B  count  Raw data counts in ECF90 aperture ACIS b band  100  long  1J  
SRC_AMPL_B  photon/cm**2/s  Best fit point src model amplitude ACIS b band  1.00E08  double  1D  
SRC_AMPL_LOLIM_B  photon/cm**2/s  68% confidence lower limit on SRC_AMPL_B  9.00E09  double  1D  
SRC_AMPL_HILIM_B  photon/cm**2/s  68% confidence upper limit on SRC_AMPL_B  1.10E08  double  1D  
SRC_RDATA_S  count  Raw data counts in ECF90 aperture ACIS s band  30  long  1J  
SRC_AMPL_S  photon/cm**2/s  Best fit point src model amplitude ACIS s band  3.00E09  double  1D  
SRC_AMPL_LOLIM_S  photon/cm**2/s  68% confidence lower limit on SRC_AMPL_S  2.00E09  double  1D  
SRC_AMPL_HILIM_S  photon/cm**2/s  68% confidence upper limit on SRC_AMPL_S  4.00E09  double  1D  
SRC_RDATA_M  count  Raw data counts in ECF90 aperture ACIS m band  50  long  1J  
SRC_AMPL_M  photon/cm**2/s  Best fit point src model amplitude ACIS m band  5.00E09  double  1D  
SRC_AMPL_LOLIM_M  photon/cm**2/s  68% confidence lower limit on SRC_AMPL_M  4.00E10  double  1D  
SRC_AMPL_HILIM_M  photon/cm**2/s  68% confidence upper limit on SRC_AMPL_M  6.00E09  double  1D  
SRC_RDATA_H  count  Raw data counts in ECF90 aperture ACIS h band  20  long  1J  
SRC_AMPL_H  photon/cm**2/s  Best fit point src model amplitude ACIS h band  2.00E09  double  1D  
SRC_AMPL_LOLIM_H  photon/cm**2/s  68% confidence lower limit on SRC_AMPL_H  1.00E09  double  1D  
SRC_AMPL_HILIM_H  photon/cm**2/s  68% confidence upper limit on SRC_AMPL_H  3.00E09  double  1D  
SRC_RDATA_W  count  Raw data counts in ECF90 aperture HRC w band  TNULL  long  1J  
SRC_AMPL_W  photon/cm**2/s  Best fit point src model amplitude HRC w band  NaN  double  1D  
SRC_AMPL_LOLIM_W  photon/cm**2/s  68% confidence lower limit on SRC_AMPL_W  NaN  double  1D  
SRC_AMPL_HILIM_W  photon/cm**2/s  68% confidence upper limit on SRC_AMPL_W  NaN  double  1D  
EBAND_EXT  Energy band of extended source model properties  's'  string  1A  Energy band corresponding to reported extended source parameters: set to ' ' if not evaluated, otherwise one of 'b', 'u', 's', 'm', 'h', or 'w'.  
EXTSRC_CLASS  Extended source classification  'POSSIBLE'  string  8A  'POINT', 'EXTENDED', or 'POSSIBLE'  
EXT_RDATA  count  Raw data counts in source region aperture  40  long  1J  
EXT_AMPL  photon/cm**2/s  Best fit ext src model amplitude  2.50E09  double  1D  
EXT_AMPL_LOLIM  photon/cm**2/s  68% confidence lower limit on EXT_AMPL  1.50E09  double  1D  
EXT_AMPL_HILIM  photon/cm**2/s  68% confidence upper limit on EXT_AMPL  3.50E09  double  1D  
EXT_SMAJ  arcsec  Best fit extended source model semimajor axis  5.0  double  1D  
EXT_SMIN  arcsec  Best fit extended source model semiminor axis  3.5  double  1D  
EXT_ROTANG  deg  Best fit extended source model rotation angle  30.0  double  1D  
EXT_SMAJ_LOLIM  arcsec  68% confidence lower limit on EXT_SMAJ  4.5  double  1D  
EXT_SMAJ_HILIM  arcsec  68% confidence upper limit on EXT_SMAJ  5.5  double  1D  
EXT_SMIN_LOLIM  arcsec  68% confidence lower limit on EXT_SMIN  3.0  double  1D  
EXT_SMIN_HILIM  arcsec  68% confidence upper limit on EXT_SMIN  4.0  double  1D  
EXT_ROTANG_LOLIM  deg  68% confidence lower limit on EXT_ROTANG  10.0  double  1D  
EXT_ROTANG_HILIM  deg  68% confidence upper limit on EXT_ROTANG  50.0  double  1D 
Caveats

This version of the preliminary detections table is constructed from a partial run of Chandra observations that will be included in release 2.0 of the CSC, and includes 362,182 detections from 7,247 observation stacks.

Roughly 0.5% of observation stacks have not yet completed processing or are awaiting manual quality assurance review. The list of observation stacks not included in this version of the preliminary detections table is reported in Table 1.

The preliminary detections table includes detections and not sources. In particular:

Sources that are detected in multiple observation stacks are not combined in any way. Each detection is reported separately.

Offaxis detections from one observation stack may correspond to multiple detections in another observation stack where the detections are onaxis. These matches will be resolved in second major catalog processing phase.

As a consequence, source names have not yet been assigned. Instead, an identifier has been provided for each detection. Note that the identifiers included in this version of the preliminary detections table may not match the identifiers included in the August 2015 version of the table because a significant fraction of the observation stacks required complete reprocessing since then.


Detections:

A small number of compact detections identified as definitely or possibly extended (extsrc_class = ‘EXTENDED’ or ‘POSSIBLE’) may consist of a close association (typically a pair or triple) of point detections. These will not be corrected in the final catalog.

Detections that are extremely piledup (cratered) have likelihood = +Inf. A very small number (of order 10) of these detections are incorrectly classified and will be corrected in the final catalog.


Positions and position errors:

Position errors are typically reported in the form of an error ellipse that records the statistical confidence limits derived from a Markov chain Monte Carlo (MCMC) analysis of the fitted source model. The ellipse angle in the preliminary detections table defines 0° along the +X axis (i.e., the same definition as used by the DS9 imager); however, true astronomical position angles (measured from North through East) will be used in the final catalog.

If the MCMC analysis did not converge (typically due to low S/N) then a circularly symmetric estimate of the position errors is provided.

Reported position errors do not include the absolute uncertainty in the astrometry relative to the reference frame. The systematic error derived from release 1 of the catalog (0.16″ radial) should be a reasonable estimate of this value, and this number should be added in quadrature to the report position errors to get the best estimate of the absolute position uncertainty on the sky.


Aperture photometry:

Fit amplitudes are provided as proxies for the full Bayesian aperture photometry analysis that will be included in the final catalog (see Figure 1). While these are expected to be reasonably reliable for relative photometry on a statistical basis, systematic uncertainties for a single detection basis may be large. Detailed Bayesian Xray aperture photometry for each source will be calculated as part of the second major catalog processing phase.


Miscellaneous notes:

The detections have undergone all standard quality assurance reviews, and except for the caveats noted herein should match those that will be included in the final catalog.

Detections identified near the edges of (stacked observation) fields, near edges of individual observations within observation stacks, near areas of extended emission, and on readout streaks, may have a higher than nominal false detection rate. If this is a concern, we recommend that users review images of the individual observations from the Chandra Data Archive.

Detections are categorized as ‘MARGINAL’ or ‘TRUE’ (recorded under src_quality) depending on their likelihood. These categorizations are those that will appear in the final catalog.

Detections near the edges of the field of each observation, or near the gap between adjacent backilluminated and frontilluminated ACISS CCDs, or on bright ACIS readout streaks, are not included. This is intentional because these detector areas had an excessively high false source rate in release 1 of the catalog. In the final catalog release, the detection sensitivity will be set to zero in these areas. However, detection sensitivity information will not be available until completion of the second major catalog processing phase.

Only point and compact detections are included. Extended (“convex hull”) detections are not included in the preliminary detections table, but will appear in the final catalog release.

acisfJ0011407m152147_001  acisfJ0319443p413138_001  acisfJ0534316p220052_001 
acisfJ0534322p215837_001  acisfJ0534340p221143_001  acisfJ0535165m052323_001 
acisfJ0538411m690602_001  acisfJ0955442p694142_001  acisfJ1047086m600555_001 
acisfJ1047429p135930_001  acisfJ1048174p123757_001  acisfJ1115042m611530_001 
acisfJ1124354m591559_001  acisfJ1214458m652812_001  acisfJ1230487p122327_001 
acisfJ1325492m425819_001  acisfJ1325538m425945_001  acisfJ1330038p471057_001 
acisfJ1424365p225555_001  acisfJ1501079p014443_001  acisfJ1513347m590144_001 
acisfJ1513347m590144_001  acisfJ1523045p083741_001  acisfJ1611413m014634_001 
acisfJ1712268m232325_001  acisfJ1713442m370615_001  acisfJ1721036m372619_001 
acisfJ1745401m290028_001  acisfJ1748454m271007_001  acisfJ1800276m240230_001 
acisfJ1846224m025742_001  acisfJ1907327p070619_001  acisfJ2208400p454446_001 
acisfJ2239250m054359_001  acisfJ2308192m020958_001  acisfJ2323333p584655_001 
acisfJ2323335p585100_001  acisfJ2323390p585033_001  acisfJ2343503m151712_001 
hrcfJ0044069p414315_001 