Chandra X-Ray Observatory
Skip to the navigation links
Last modified: 3 August 2015


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 August 2015 release of the Chandra Source Catalog Release 2.0 Preliminary 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.

Production of release 2.0 of the Chandra Source Catalog (CSC) started in late April 2015!

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 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.

Production of release 2.0 of the CSC will require many months to run, even using a dedicated compute-cluster. When complete, the catalog should include information for of order 400,000 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 of 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 expected complete in (Northern) autumn 2015.

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 table will be incrementally updated on the catalog website as processing progresses. 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 release notes for the preliminary detections table.

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 is expected to be completed in (Northern) spring 2016.

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

Last modified: 3 August 2015
Smithsonian Institute Smithsonian Institute

The Chandra X-Ray Center (CXC) is operated for NASA by the Smithsonian Astrophysical Observatory. 60 Garden Street, Cambridge, MA 02138 USA.   Email: Smithsonian Institution, Copyright © 1998-2016. All rights reserved.