CSC 2.0 pd1 Preliminary Detections List (21 March 2017)
Please see the September 2017 preliminary detections list (CSC 2.0 pd2).
Contents
Data Access
The March 2017 preliminary detections list 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  Data type  Notes  Example 

DETECT_ID  Stack_id.component  string (29 characters)  'acisfJ0123456p012345_001.0001'  
LIKELIHOOD  Highest source log likelihood  double  Highest source likelihood  100.0  
SRC_QUALITY  Preliminary source quality  string (8 characters)  Values are 'TRUE' or 'MARGINAL' and are based on comparison of likelihood with draft catalog thresholds.  'TRUE'  
EBAND  Energy band of maximum likelihood value  string (1 character)  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'.  'b'  
THETA  arcmin  Highest likelihood src model mean offaxis ang  double  Corresponds to fitted [x,y]  0.0 
STREAK_SRC_FLAG  Is source on a streak?  logical  'F'  
RA  deg  Highest likelihood source model position RA  double  20.94000  
DEC  deg  Highest likelihood source model position Dec  double  1.39583  
ERR_ELLIPSE_RA  deg  95% confidence error ellipse position RA  double  95% confidence error ellipse RA in deg; 0.0 <= ERR_ELLIPSE_RA < 360.0  20.94000 
ERR_ELLIPSE_DEC  deg  95% confidence error ellipse position Dec  double  95% confidence error ellipse Dec in deg; 90.0 <= SRC_ERR_ELLIPSE_DEC_B <= +90.0  1.39583 
ERR_ELLIPSE_R0  arcsec  95% confidence error ellipse semimajor axis  double  95% confidence error ellipse semimajor axis radius in arcsec  0.35 
ERR_ELLIPSE_R1  arcsec  95% confidence error ellipse semiminor axis  double  95% confidence error ellipse semiminor axis radius in arcsec  0.30 
ERR_ELLIPSE_ANG  deg  95% confidence error ellipse smaj axis rotang  double  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  60.0 
SRC_RDATA_B  count  Raw data counts in ECF90 aperture ACIS b band  long  100  
SRC_AMPL_B  photon/cm**2/s  Best fit point src model amplitude ACIS b band  double  1.00E08  
SRC_AMPL_LOLIM_B  photon/cm**2/s  68% confidence lower limit on SRC_AMPL_B  double  9.00E09  
SRC_AMPL_HILIM_B  photon/cm**2/s  68% confidence upper limit on SRC_AMPL_B  double  1.10E08  
SRC_RDATA_S  count  Raw data counts in ECF90 aperture ACIS s band  long  30  
SRC_AMPL_S  photon/cm**2/s  Best fit point src model amplitude ACIS s band  double  3.00E09  
SRC_AMPL_LOLIM_S  photon/cm**2/s  68% confidence lower limit on SRC_AMPL_S  double  2.00E09  
SRC_AMPL_HILIM_S  photon/cm**2/s  68% confidence upper limit on SRC_AMPL_S  double  4.00E09  
SRC_RDATA_M  count  Raw data counts in ECF90 aperture ACIS m band  long  50  
SRC_AMPL_M  photon/cm**2/s  Best fit point src model amplitude ACIS m band  double  5.00E09  
SRC_AMPL_LOLIM_M  photon/cm**2/s  68% confidence lower limit on SRC_AMPL_M  double  4.00E10  
SRC_AMPL_HILIM_M  photon/cm**2/s  68% confidence upper limit on SRC_AMPL_M  double  6.00E09  
SRC_RDATA_H  count  Raw data counts in ECF90 aperture ACIS h band  long  20  
SRC_AMPL_H  photon/cm**2/s  Best fit point src model amplitude ACIS h band  double  2.00E09  
SRC_AMPL_LOLIM_H  photon/cm**2/s  68% confidence lower limit on SRC_AMPL_H  double  1.00E09  
SRC_AMPL_HILIM_H  photon/cm**2/s  68% confidence upper limit on SRC_AMPL_H  double  3.00E09  
SRC_RDATA_W  count  Raw data counts in ECF90 aperture HRC w band  long  TNULL  
SRC_AMPL_W  photon/cm**2/s  Best fit point src model amplitude HRC w band  double  NaN  
SRC_AMPL_LOLIM_W  photon/cm**2/s  68% confidence lower limit on SRC_AMPL_W  double  NaN  
SRC_AMPL_HILIM_W  photon/cm**2/s  68% confidence upper limit on SRC_AMPL_W  double  NaN  
EBAND_EXT  Energy band of extended source model properties  string (1 character)  Energy band corresponding to reported extended source parameters: set to ' ' if not evaluated, otherwise one of 'b', 'u', 's', 'm', 'h', or 'w'.  's'  
EXTSRC_CLASS  Extended source classification  string (8 characters)  'POINT', 'EXTENDED', or 'POSSIBLE'  'POSSIBLE'  
EXT_RDATA  count  Raw data counts in source region aperture  long  40  
EXT_AMPL  photon/cm**2/s  Best fit ext src model amplitude  double  2.50E09  
EXT_AMPL_LOLIM  photon/cm**2/s  68% confidence lower limit on EXT_AMPL  double  1.50E09  
EXT_AMPL_HILIM  photon/cm**2/s  68% confidence upper limit on EXT_AMPL  double  3.50E09  
EXT_SMAJ  arcsec  Best fit extended source model semimajor axis  double  5.0  
EXT_SMIN  arcsec  Best fit extended source model semiminor axis  double  3.5  
EXT_ROTANG  deg  Best fit extended source model rotation angle  double  30.0  
EXT_SMAJ_LOLIM  arcsec  68% confidence lower limit on EXT_SMAJ  double  4.5  
EXT_SMAJ_HILIM  arcsec  68% confidence upper limit on EXT_SMAJ  double  5.5  
EXT_SMIN_LOLIM  arcsec  68% confidence lower limit on EXT_SMIN  double  3.0  
EXT_SMIN_HILIM  arcsec  68% confidence upper limit on EXT_SMIN  double  4.0  
EXT_ROTANG_LOLIM  deg  68% confidence lower limit on EXT_ROTANG  double  10.0  
EXT_ROTANG_HILIM  deg  68% confidence upper limit on EXT_ROTANG  double  50.0 
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 CSC 2.0 release.

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 CSC 2.0 release.


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 CSC 2.0 release.

If the MCMC analysis did not converge (typically due to low S/N) then a circularly symmetric estimate of the position errors is provided. For a small number (~240) detections, this estimate is missing and the reported errors are blank. This will be corrected in the CSC 2.0 release of the catalog.

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 reported position errors to get the best estimate of the absolute position uncertainty on the sky.


Aperture photometry:

Fit amplitudes are provided as a proxy for the detection flux: 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. As a guide to possible biases, Figure 1 compares  for a subset of the pd1 release  the fit amplitudes to aperture photometry calculated using the Bayesian Xray photometry scheme that will be used in the CSC 2.0 release.

Reported fit amplitudes are incorrect (significantly too large) for one or more energy bands for ~3,500 detections. The broad band flux is equal to the sum of the soft, medium, and hard band fluxes. These cases can be identified by comparing the sum of the reported soft, medium, and hard band fit amplitudes with the reported broad band fit amplitude.


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 CSC 2.0 release.

Detections are categorized as ‘MARGINAL’ or ‘TRUE’ (recorded in the SRC_QUALITY column) depending on their likelihood. These categorizations are those that will appear in the CSC 2.0 release.

Only point and compact detections are included. Extended (“convex hull”) detections are not included in the preliminary detections table, but will appear in the CSC 2.0 release.

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 masked out. This is intentional because these detector areas had an excessively high false source rate in release 1 of the catalog. In the CSC 2.0 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. There may be a higherthannominal false detection rate either near these maskedout regions or close to areas of extended emission. If this is a concern, we recommend that users review images of the individual observations from the Chandra Data Archive.

Area of sky  Stack ID  Number of observations  Approximate exposure time, in ks  Observations 

MACS0011.71523  acisfJ0011407m152147_001  1  40  6105 
Perseus Cluster (Abell 426)  acisfJ0319443p413138_001  11  800  4946, 4947, 4948, 4949, 4950, 4951, 4952, 4953, 6139, 6145, 6146 
Crab Nebula  acisfJ0534316p220052_001  45  769, 770, 771, 772, 773, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 13139, 13146, 13147, 13150, 13151, 13152, 13153, 13154, 13204, 13205, 13206, 13207, 13208, 13209, 13210, 13750_001, 13751, 13752, 13754, 13755, 13756, 13757, 14416, 14458, 14678, 14679, 14680, 14681, 14682, 14685, 16245, 16257  
acisfJ0534322p215837_001  1  4607  
acisfJ0534340p221143_001  1  20  2798  
Orion Trapezium cluster  acisfJ0535165m052323_001  11  990  1522, 3498, 3744, 4373, 4374, 4395, 4396, 13637, 14334, 14335, 15546 
30 Doradus  acisfJ0538411m690602_001  30  1520  5906, 7263, 7264, 16192, 16193, 16194, 16195, 16196, 16197, 16198, 16200, 16201, 16202, 16203, 16442, 16443, 16444, 16612, 16615, 16616, 16617, 16621, 16640, 17312, 17413, 17414, 17486, 17544, 17545, 17555, 17561, 17562 
M82 (North West)  acisfJ0955442p694142_001  1  120  10543 
The Great Nebula in Carina  acisfJ1047086m600555_001  1  60  9485 
NGC 3377  acisfJ1047429p135930_001  1  40  2934 
NGC 3384  acisfJ1048174p123757_001  3  140  4692, 11782, 13829 
NGC 3603  acisfJ1115042m611530_001  5  520  633, 12328, 12329, 12330, 13162 
G292.0+1.8  acisfJ1124354m591559_001  6  540  6677, 6678, 6679, 6680, 8221, 8447 
G299.22.9  acisfJ1214458m652812_001  9  660  11098, 11099, 11100, 11101, 13157, 13158, 13159, 13160, 13187 
M87  acisfJ1230487p122327_001  44  340  6186, 7348, 7349, 7350, 7351, 7352, 7353, 7354, 8510, 8511, 8512, 8513, 8514, 8515, 8516, 8517, 8575, 8576, 08577, 8578, 8579, 8580, 8581, 10282, 10283, 10284, 10285, 10286, 10287, 10288, 11512, 11513, 11514, 11515, 11516, 11517, 11518, 11519, 11520, 13964, 13965, 14973, 14974, 16042 
Centaurus A  acisfJ1325492m425819_001  4  120  7800, 10723, 10726, 12155 
acisfJ1325538m425945_001  2  190  7798, 07799  
M51  acisfJ1330038p471057_001  7  770  13812, 13813, 13814, 13815, 13816, 15496, 15553 
Q1422+231  acisfJ1424365p225555_001  3  80  367, 1631, 12801 
NGC 5813  acisfJ1501079p014443_001  7  510  12951, 12952, 12953, 13246, 13247, 13253, 13255 
RCW89  acisfJ1513347m590144_001  2  90  5562, 9138 
Abell 2063  acisfJ1523045p083741_001  4  60  4187, 5795, 6262, 6263 
F160900139  acisfJ1611413m014634_001  1  10  4113 
Ophiuchus cluster  acisfJ1712268m232325_001  1  50  3200 
NGC 6302  acisfJ1713442m370615_001  2  30  12370, 14364 
G350.10.3  acisfJ1721036m372619_001  1  90  10102 
Sagittarius A*  acisfJ1745401m290028_001  70  2460  1561, 2943, 2951, 2952, 2953, 2954, 3392, 3393, 3549, 3663, 3665, 4683, 4684, 5360, 5950, 5951, 5952, 5953, 5954, 6113, 6363, 6639, 6640, 6641, 6642, 6643, 6644, 6645, 6646, 7554, 7555, 7556, 7557, 7558, 7559, 9169, 9170, 9171, 9172, 9173, 9174, 10556, 11843, 13016, 13017, 14702, 14703, 14704_001, 14941, 14942, 14943, 14944, 14945, 14946, 15041, 15042, 15043, 15044, 15045, 16210, 16211, 16212, 16213, 16214, 16215, 16216, 16217, 16218, 16508, 16597 
G1.9+0.3  acisfJ1748454m271007_001  15  1310  6708, 8521, 10111, 10112, 10928, 10930, 12689, 12690, 12691, 12692, 12693, 12694, 12695, 13407, 13509 
HESS J1800240B (W28)  acisfJ1800276m240230_001  1  10997  
Kes 75  acisfJ1846224m025742_001  4  6686, 7337, 7338, 7339  
3C397  acisfJ1907327p070619_001  1  1042  
Ar Lac (calibration target)  acisfJ2208400p454446_001  4  9686, 9687, 9688, 9689  
Abell 2465  acisfJ2239250m054359_001  2  14010, 15547  
Abell 2537  acisfJ2308192m020958_001  1  9372  
Cassiopeia A  acisfJ2323333p584655_001  3  1547, 9117, 9773  
acisfJ2323335p585100_001  6  4634, 4635, 5320, 10643, 14229, 14480  
acisfJ2323390p585033_001  6  4636, 4637, 4638, 4639, 5319, 6068  
R Aquarii  acisfJ2343503m151712_001  3  651, 4546, 5438  
M31 (North)  hrcfJ0044069p414315_001  15  30  279, 282, 283, 284, 285, 287, 288, 289, 290, 1571, 1572, 2907, 2908, 2909, 2910 