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Last modified: 21 March 2017


The Chandra Source Catalog

Release 2.0

[Thumbnail image: The detections are spread across the sky.]

[Version: full-size]

[Print media version: The detections are spread across the sky.]

Preliminary detections

The locations of the detections provided in the March 2017 release of the Chandra Source Catalog Release 2.0 Detections List. Note that, as described in the caveats, the coverage of the Chandra archive is incomplete, with only a subset of ACIS and HRC-I fields included, and the display shows detections rather than sources.

Release 2.0 of the CSC will include data from observations released publicly through the end of 2014, and will include fainter sources than the current release (1.1) of the catalog. This is achieved by stacking (summing) multiple observations of the same field (all pointings co-located within 60 arcsec diameter) obtained with the same instrument prior to source detection, and by using an improved source detection method that allows us to reliably detect point sources down to roughly 5 net counts on-axis, for exposures shorter than the median Chandra observation duration. When complete, the catalog should include information for about 370,000 source detections from roughly 10,000 Chandra ACIS and HRC-I imaging observations.

To facilitate user access to the catalog as quickly as possible, production is being split into two major phases. The first phase recalibrates all the Chandra data sets that are included in release 2.0, generates backgrounds, performs source detection, and then evaluates the candidate detections’ likelihoods using a new maximum likelihood estimator tool. This phase is now ~99.5% complete, and is missing a small number of fields that require additional manual quality assurance review that will be performed over the next few months.

Key data for each detection from this phase of processing are being made available to the community in the form of a FITS binary preliminary detections table. 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. This table will be incrementally updated on the catalog website as processing progresses.

The Preliminary CSC 2.0 List

Users can retrieve and learn more about the preliminary detection list of the production version of CSC 2.0 (March 2017).

The preliminary detections table include positions, likelihoods, extents, and associated errors. Error estimates will be preliminary. True aperture photometry is not available, although a fitted detection amplitude that is a reasonably good proxy (except in the Poisson regime) is included. For more information, see the table of data contents.

Properties derived from true aperture photometry, such as hardness ratios, spectral information, and variability measures, are computed in the second major catalog production phase, which will be completed in the second half of 2017.

This is a work in progress! Be sure to read the notes and caveats provided below prior to using these data!

News updates about release 2.0 of the catalog will be added to the catalog website as processing progresses.

Last modified: 21 March 2017
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