Chandra's First Decade of Discovery

Chandra Source Catalog

Chandra Source Catalog: User Interface

Nina Bonaventura, Smithsonian Astrophysical Observatory
Ian N. Evans (SAO), Arnold H. Rots (SAO), Michael S. Tibbetts (SAO), David W. Van Stone (SAO), Panagoula Zografou (SAO), Francis A. Primini (SAO), Kenny J. Glotfelty (SAO), Craig S. Anderson (SAO), Judy C. Chen (SAO), John E. Davis (MIT), Stephen M. Doe (SAO), Janet D. Evans (SAO), Giuseppina Fabbiano (SAO), Elizabeth Galle (SAO), Danny G. Gibbs II (SAO), John D. Grier (SAO), Roger Hain (SAO), Diane M. Hall (NGIS), Peter N. Harbo (SAO), Xiangqun (Helen) He (SAO), John C. Houck (MIT), Margarita Karovska (SAO), Vinay L. Kashyap (SAO), Jennifer Lauer (SAO), Michael L. McCollough (SAO), Jonathan C. McDowell (SAO), Joseph B. Miller (SAO), Arik W. Mitschang (SAO), Douglas L. Morgan (SAO), Amy E. Mossman (SAO), Joy S. Nichols (SAO), Michael A. Nowak (MIT), David A. Plummer (SAO), Brian L. Refsdal (SAO), Aneta L. Siemiginowska (SAO), Beth A. Sundheim (SAO), Sherry L. Winkelman (SAO)

The Chandra Source Catalog (CSC) is intended to be the definitive catalog of all X-ray sources detected by Chandra. For each source, the CSC provides positions and multi-band fluxes, as well as derived spatial, spectral, and temporal source properties. Full-field and source region data products are also available, including images, photon event lists, light curves, and spectra. The Chandra X-ray Center CSC website (http://cxc.harvard.edu/csc/) is the place to visit for high-level descriptions of each source property and data product included in the catalog, along with other useful information, such as step-by-step catalog tutorials, answers to FAQs, and a thorough summary of the catalog statistical characterization. Eight categories of detailed catalog documents may be accessed from the navigation bar on most of the 50+ CSC pages; these categories are: About the Catalog, Creating the Catalog, Using the Catalog, Catalog Columns, Column Descriptions, Documents, Conferences, and Useful Links. There are also prominent links to CSCview, the CSC data access GUI, and related help documentation, as well as a tutorial for using the new CSC/Google Earth interface. Catalog source properties are presented in seven scientific categories, within two table views: the Master Source and Source Observations tables. Each X-ray source has one “master source” entry and one or more “source observation” entries, the details of which are documented on the CSC “Catalog Columns” pages. The master source properties represent the best estimates of the properties of a source; these are extensively described on the following pages of the website: Position and Position Errors, Source Flags, Source Extent and Errors, Source Fluxes, Source Significance, Spectral Properties, and Source Variability. The eight tutorials (“threads”) available on the website serve as a collective guide for accessing, understanding, and manipulating the source properties and data products provided by the catalog.

The Chandra Source Catalog: Spectral Properties

Stephen Doe, Smithsonian Astrophysical Observatory
Aneta L. Siemiginowska (SAO), Brian L. Refsdal (SAO), Ian N. Evans (SAO), Craig S. Anderson (SAO), Nina R. Bonaventura (SAO), Judy C. Chen (SAO), John E. Davis (MIT), Janet D. Evans (SAO), Giuseppina Fabbiano (SAO), Elizabeth Galle (SAO), Danny G. Gibbs II (SAO), Kenny J. Glotfelty (SAO), John D. Grier (SAO), Roger Hain (SAO), Diane M. Hall (NGIS), Peter N. Harbo (SAO), Xiang qun (Helen) He (SAO), John C. Houck (MIT), Margarita Karovska (SAO), Vinay L. Kashyap (SAO), Jennifer Lauer (SAO), Michael L. McCollough (SAO), Jonathan C. McDowell (SAO), Joseph B. Miller (SAO), Arik W. Mitschang (SAO), Douglas L. Morgan (SAO), Amy E. Mossman (SAO), Joy S. Nichols (SAO), Michael A. Nowak (MIT), David A. Plummer (SAO), Francis A. Primini (SAO), Arnold H. Rots (SAO), Beth A. Sundheim (SAO), Michael S. Tibbetts (SAO), David W. Van Stone (SAO), Sherry L. Winkelman (SAO), and Panagoula Zografou (SAO)

The first release of the Chandra Source Catalog (CSC) contains all sources identified from eight years' worth of publicly accessible observations. The vast majority of these sources have been observed with the ACIS detector and have spectral information in 0.5-7 keV energy range. Here we describe the methods used to automatically derive spectral properties for each source detected by the standard processing pipeline and included in the final CSC. Hardness ratios were calculated for each source between pairs of energy bands (soft, medium and hard) using the Bayesian algorithm (BEHR, Park et al. 2006). The sources with high signal to noise ratio (exceeding 150 net counts) were fit in Sherpa (the modeling and fitting application from the Chandra Interactive Analysis of Observations package, developed by the Chandra X-ray Center; see Freeman et al. 2001). Two models were fit to each source: an absorbed power law and a blackbody emission. The fitted parameter values for the power-law and blackbody models were included in the catalog with the calculated flux for each model. The CSC also provides the source energy flux computed from the normalizations of predefined power-law and black-body models needed to match the observed net X-ray counts. In addition, we provide access to data products for each source: a file with source spectrum, the background spectrum, and the spectral response of the detector. This work is supported by NASA contract NAS8-03060 (CXC).

The Chandra Source Catalog

Ian Evans, SAO
Francis A. Primini (SAO), Kenny J. Glotfelty (SAO), Craig S. Anderson (SAO), Nina R. Bonaventura (SAO), Judy C. Chen (SAO), John E. Davis (MIT), Stephen M. Doe (SAO), Janet D. Evans (SAO), Giuseppina Fabbiano (SAO), Elizabeth Galle (SAO), Danny G. Gibbs (SAO), John D. Grier (SAO), Roger Hain (SAO), Diane M. Hall (NGIS), Peter N. Harbo (SAO), Xiangqun (Helen) He (SAO), John C. Houck (MIT), Margarita Karovska (SAO), Vinay L. Kashyap (SAO), Jennifer Lauer (SAO), Michael L. McCollough (SAO), Jonathan C. McDowell (SAO), Joseph B. Miller (SAO), Arik W. Mitschang (SAO), Douglas L. Morgan (SAO), Amy E. Mossman (SAO), Joy S. Nichols (SAO), Michael A. Nowak (MIT), David A. Plummer (SAO), Brian L. Refsdal (SAO), Arnold H. Rots (SAO), Aneta L. Siemiginowska (SAO), Beth A. Sundheim (SAO), Michael S. Tibbetts (SAO), David W. Van Stone (SAO), Sherry L. Winkelman (SAO), Panagoula Zografou (SAO)

The first release of the Chandra Source Catalog (CSC) was published in 2009 March, and includes information about 94,676 X-ray sources detected in a subset of public ACIS imaging observations from roughly the first eight years of the Chandra mission. This release of the catalog includes point and compact sources with observed spatial extents < ~30". The CSC is a general purpose virtual X-ray astrophysics facility that provides access to a carefully selected set of generally useful quantities for individual X-ray sources, and is designed to satisfy the needs of a broad-based group of scientists, including those who may be less familiar with astronomical data analysis in the X-ray regime. The catalog (1) provides access to the best estimates of the X-ray source properties for detected sources, with good scientific fidelity, and directly supports medium sophistication scientific analysis on using the individual source data; (2) facilitates analysis of a wide range of statistical properties for classes of X-ray sources; (3) provides efficient access to calibrated observational data and ancillary data products for individual X-ray sources, so that users can perform detailed further analysis using existing tools; and (4) includes real X-ray sources detected with flux significance greater than a predefined threshold, while maintaining the number of spurious sources at an acceptable level. For each detected X-ray source, the CSC provides commonly tabulated quantities, including source position, extent, multi-band fluxes, hardness ratios, and variability statistics, derived from the observations in which the source is detected. In addition to these traditional catalog elements, for each X-ray source the CSC includes an extensive set of file-based data products that can be manipulated interactively, including source images, event lists, light curves, and spectra from each observation in which a source is detected.

The Chandra Source Catalog: Processing and Infrastructure

Janet Evans, SAO
Ian N. Evans (SAO), Kenny J. Glotfelty (SAO),Roger Hain (SAO), Diane M. Hall (NGIS), Joseph B. Miller (SAO),David A. Plummer (SAO), Panagoula Zografou (SAO), Francis A. Primini (SAO), Craig S. Anderson (SAO), Nina R. Bonaventura (SAO), Judy C. Chen (SAO),John E. Davis (MIT), Stephen M. Doe (SAO), Giuseppina Fabbiano (SAO), Elizabeth Galle (SAO), Danny G. Gibbs II (SAO), John D. Grier (SAO), Peter N. Harbo (SAO), Xiangqun (Helen) He (SAO), John C. Houck (MIT),Margarita Karovska (SAO), Vinay L. Kashyap (SAO), Jennifer Lauer (SAO), Michael L. McCollough (SAO), Jonathan C. McDowell (SAO), Arik W. Mitschang (SAO), Douglas L. Morgan (SAO), Amy E. Mossman (SAO), Joy S. Nichols (SAO), Michael A. Nowak (MIT), Brian L. Refsdal (SAO),Arnold H. Rots (SAO), Aneta L. Siemiginowska (SAO), Beth A. Sundheim (SAO), Michael S. Tibbetts (SAO), David W. Van Stone (SAO), Sherry L. Winkelman (SAO)

Chandra Source Catalog processing recalibrates each observation using the latest available calibration data, and employs a wavelet-based source detection algorithm to identify all the X-ray sources in the field of view. Source properties are then extracted from each detected source that is a candidate for inclusion in the catalog. Catalog processing is completed by matching sources across multiple observations, merging common detections, and applying quality assurance checks. The Chandra Source Catalog processing system shares a common processing infrastructure and utilizes much of the functionality that is built into the Standard Data Processing (SDP) pipeline system that provides calibrated Chandra data to end-users. Other key components of the catalog processing system have been assembled from the portable CIAO data analysis package. Minimal new software tool development has been required to support the science algorithms needed for catalog production. Since processing pipelines must be instantiated for each detected source, the number of pipelines that are run during catalog construction is a factor of order 100 times larger than for SDP. The increased computational load, and inherent parallel nature of the processing, is handled by distributing the workload across a multi-node Beowulf cluster. Modifications to the SDP automated processing application to support catalog processing, and extensions to Chandra Data Archive software to ingest and retrieve catalog products, complete the upgrades to the infrastructure to support catalog processing.

The Chandra Source Catalog: Google Earth Interface

Kenny Glotfelty, SAO
W. McLaughlin (NGST), I. Evans (SAO), J. Evans (SAO), C.S. Anderson (SAO), N.R. Bonaventura (SAO), J.C.Chen (SAO), J.E. Davis (MIT), S.M. Doe (SAO), G. Fabbiano (SAO), E. Galle (SAO), D.G. Gibbs (SAO), J.D. Grier (SAO), R. Hain (SAO), D.M. Hall (NGST), P.N. Harbo (SAO), H. He (SAO), J.C. Houck (MIT), M. Karovska (SAO), V.L. Kashyap (SAO), J. Lauer (SAO), M.L. McCollough (SAO), J.C. McDowell (SAO), J.B. Miller (SAO), A.W. Mitschang (SAO), D.L. Morgan (SAO), A.E. Mossman (SAO), J.S. Nichols (SAO), M.A. Nowak (MIT), D.A. Plummer (SAO), F.A. Primini (SAO), B.L. Refsdal (SAO), A.R. Rots (SAO), A.L. Siemiginowska (SAO), B.A. Sundheim (SAO), M.S. Tibbetts (SAO), D. W. Van Stone (SAO), S.L. Winkelman (SAO), P. Zografou (SAO)

The Chandra Source Catalog (CSC) contains multi-resolution, exposure corrected, background subtracted, full-field images that are stored as individual FITS files and as three-color JPEG files. In this poster we discuss how we took these data and were able to, with relatively minimal effort, convert them for use with the Google Earth application in its “Sky” mode. We will highlight some of the challenges which include converting the data to the required Mercator projection, reworking the 3-color algorithm for pipeline processing, and ways to reduce the data volume through re-binning, using color-maps, and special Keyhole Markup Language (kml) tags to only load images on-demand. The result is a collection of some 11,000 3-color images that are available for all the individual observation in the CSC Release 1. We also have made available all ~4000 Field-of-View outlines (with per-chip regions), which turns out are trivial to produce starting with a simple dmlist command. In the first week of release, approximately 40% of the images have been accessed at least once through some 50,000 individual web hits which have served over 4Gb of data to roughly 750 users in 60+ countries. We will also highlight some future directions we are exploring, including real-time catalog access to individual source properties and eventual access to file based products such as FITS images, spectra, and light-curves.

[PDF of this poster]

The Chandra Source Catalog: Automated Source Correlation

Roger Hain, SAO
Ian N. Evans (SAO), Janet D. Evans (SAO), Kenny J. Glotfelty (SAO),

Chandra Source Catalog (CSC) master source processing seeks to automatically detect sources and compute their properties. Since Chandra is a pointed mission and not a sky survey, different sky regions are observed for a different number of times at varying orientations, resolutions, and other heterogeneous conditions. While this provides an opportunity to collect data from a potentially large number of observing passes, it also creates challenges in determining the best way to combine different detection results for the most accurate characterization of the detected sources.The CSC master source pipeline correlates data from multiple observations by updating existing cataloged source information with new data from the same sky region as they become available. This process sometimes leads to relatively straightforward conclusions, such as when single sources from two observations are similar in size and position. Other observation results require more logic to combine, such as one observation finding a single, large source and another identifying multiple, smaller sources at the same position. We present examples of different overlapping source detections processed in the current version of the CSC master source pipeline. We explain how they are resolved into entries in the master source database, and examine the challenges of computing source properties for the same source detected multiple times. Future enhancements are also discussed. This work is supported by NASA contract NAS8-03060 (CXC).

The Chandra Source Catalog: X-ray Aperture Photometry

Vinay Kashyap, SAO
F.A. Primini (SAO), K.J. Glotfelty (SAO), C.S. Anderson (SAO), N.R. Bonaventura (SAO), J.C. Chen (SAO), J.E. Davis (MIT), S.M. Doe (SAO), I.N. Evans (SAO), J.D. Evans (SAO), G. Fabbiano (SAO), E. Galle (SAO), D.G. Gibbs (SAO), J.D. Grier (SAO), R. Hain (SAO), D.M. Hall (SAO), P.N. Harbo (SAO), X. He (SAO), J.C. Houck (MIT), M. Karovska (SAO), J. Lauer (SAO), M.L. McCollough (SAO), J.C. McDowell (SAO), J.B. Miller (SAO), A.W. Mitschang (SAO), D.L. Morgan (SAO), J.S. Nichols (SAO), M.A. Nowak (MIT), D.A. Plummer (SAO), B.L. Refsdal (SAO), A.H. Rots (SAO), A.L. Siemiginowska (SAO), B.A. Sundheim (SAO), M.S. Tibbetts (SAO), D.W. Van Stone (SAO), S.L. Winkelman (SAO), P. Zografou (SAO)

The Chandra Source Catalog (CSC) represents a reanalysis of the entire ACIS and HRC imaging observations over the 9-year Chandra mission. We describe here the method by which fluxes are measured for detected sources. Source detection is carried out on a uniform basis, using the CIAO tool wavdetect. Source fluxes are estimated post-facto using a Bayesian method that accounts for background, spatial resolution effects, and contamination from nearby sources. We use gamma-function prior distributions, which could be either non-informative, or in case there exist previous observations of the same source, strongly informative. The current implementation is however limited to non-informative priors. The resulting posterior probability density functions allow us to report the flux and a robust credible range on it.

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The Chandra Source Catalog: Background Determination and Source Detection

Michael McCollough, SAO
Arnold Rots (SAO), Francis A. Primini (SAO), Ian N. Evans (SAO), Kenny J. Glotfelty (SAO), Roger Hain (SAO), Craig S. Anderson (SAO), Nina R. Bonaventura (SAO), Judy C. Chen (SAO), John E. Davis (MIT), Stephen M. Doe (SAO), Janet D. Evans (SAO), Giuseppina Fabbiano (SAO), Elizabeth Galle (SAO), Danny G. Gibbs II (SAO), John D. Grier (SAO), Diane M. Hall (NGIS), Peter N. Harbo (SAO), Xiangqun (Helen) He (SAO), John C. Houck (MIT), Margarita Karovska (SAO), Vinay L. Kashyap (SAO), Jennifer Lauer (SAO), Michael L. McCollough (SAO), Jonathan C. McDowell (SAO), Joseph B. Miller (SAO), Arik W. Mitschang (SAO), Douglas L. Morgan (SAO), Amy E. Mossman (SAO), Joy S. Nichols (SAO), Michael A. Nowak (MIT), David A. Plummer (SAO), Brian L. Refsdal (SAO), Aneta L. Siemiginowska (SAO), Beth A. Sundheim (SAO), Michael S. Tibbetts (SAO), David W. Van Stone (SAO), Sherry L. Winkelman (SAO), and Panagoula Zografou (SAO)

The Chandra Source Catalog (CSC) is a major project in which all of the pointed imaging observations taken by the Chandra X-Ray Observatory are used to generate one of the most extensive X-ray source catalog produced to date. Early in the development of the CSC it was recognized that the ability to estimate local background levels in an automated fashion would be critical for essential CSC tasks such as source detection, photometry, sensitivity estimates, and source characterization. We present a discussion of how such background maps are created directly from the Chandra data and how they are used in source detection. The general background for Chandra observations is rather smoothly varying, containing only low spatial frequency components. However, in the case of ACIS data, a high spatial frequency component is added that is due to the readout streaks of the CCD chips. We discuss how these components can be estimated reliably using the Chandra data and what limitations and caveats should be considered in their use. We will discuss the source detection algorithm used for the CSC and the effects of the background images on the detection results. We will also touch on some the Catalog Inclusion and Quality Assurance criteria applied to the source detection results. This work is supported by NASA contract NAS8-03060 (CXC).

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The Chandra Source Catalog: Algorithms

Jonathan McDowell, SAO-CXC
Evans, I. N.; Primini, F. A.; Glotfelty, K. J.; McCollough, M. L.; Houck, J. C.; Nowak, M. A.; Karovska, M.; Davis, J. E.; Rots, A. H.; Siemiginowska, A. L.; Hain, R.; Evans, J. D.; Anderson, C. S.; Bonaventura, N. R.; Chen, J. C.; Doe, S. M.; Fabbiano, G.; Galle, E.; Gibbs, D. G.; Grier, J. D.; Hall, D. M.; Harbo, P. N.; He, X.; Lauer, J.; Miller, J. B.; Mitschang, A. W.; Morgan, D. L.; Nichols, J. S.; Plummer, D. A.; Refsdal, B. L.; Sundheim, B. A., Tibbetts, M.S., Van Stone, D.W., Winkelman, S.L., Zografou, P. (SAO)

Creation of the Chandra Source Catalog (CSC) required adjustment of existing pipeline processing, adaptation of existing interactive analysis software for automated use, and development of entirely new algorithms. Data calibration was based on the existing pipeline, but more rigorous data cleaning was applied and the latest calibration data products were used. For source detection, a local background map was created including the effects of ACIS source readout streaks. The existing wavelet source detection algorithm was modified and a set of post-processing scripts used to correct the results. To analyse the source properties we ran the SAO Traceray trace code for each source to generate a model point spread function, allowing us to find encircled energy correction factors and estimate source extent. Further algorithms were developed to characterize the spectral, spatial and temporal properties of the sources and to estimate the confidence intervals on count rates and fluxes. Finally, sources detected in multiple observations were matched, and best estimates of their merged properties derived. In this paper we present an overview of the algorithms used, with more detailed treatment of some of the newly developed algorithms presented in companion papers.

The Chandra Source Catalog: Source Variability

Michael Nowak, MIT Kavli Institute
A.H. Rots, M. L. McCollough, F. A. Primini, K. J. Glotfelty, N. R. Bonaventura, J. C. Chen, J. E. Davis, S. M. Doe, J. D. Evans, I. Evans, G. Fabbiano, E. Galle, D. G. Gibbs, J. D. Grier, R. Hain, D. M. Hall, P. N. Harbo, X. He, J. C. Houck, M. Karovska, J. Lauer, J. C. McDowell, J. B. Miller, A. W. Mitschang, D. L. Morgan, J. S. Nichols, D. A. Plummer, B. L. Refsdal, A. L. Siemiginowska, B. A. Sundheim, M. S. Tibbetts, D. W. Van Stone, S. L. Winkelman, P. Zografou

The Chandra Source Catalog (CSC) contains fields of view that have been studied with individual, uninterrupted observations that span integration times ranging from 1 ksec to 160 ksec, and a large number of which have received (multiple) repeat observations days to years later. The CSC thus offers an unprecedented look at the variability of the X-ray sky over a broad range of time scales, and across a wide diversity of variable X-ray sources: stars in the local galactic neighborhood, galactic and extragalactic X-ray binaries, Active Galactic Nuclei, etc. Here we describe the methods used to identify and quantify source variability within a single observation, and the methods used to assess the variability of a source when detected in multiple, individual observations. Three tests are used to detect source variability within a single observation: the Kolmogorov-Smirnov test and its variant, the Kuiper test, and a Bayesian approach originally suggested by Gregory and Loredo. The latter test not only provides an indicator of variability, but is also used to create a best estimate of the variable lightcurve shape. We assess the performance of these tests via simulation of statistically stationary, variable processes with arbitrary input power spectral densities (here we concentrate on results of red noise simulations) at variety of mean count rates and fractional root mean square variabilities relevant to CSC sources. We also assess the false positive rate via simulations of constant sources whose sole source of fluctuation is Poisson noise. We compare these simulations to an assessment of the variability found in real CSC sources, and estimate the variability sensitivities of the CSC.

The Chandra Source Catalog: Statistical Characterization

Francis A. Primini, SAO
Francis A. Primini (SAO), M. A. Nowak (MIT), J. C. Houck (MIT), J. E. Davis (MIT), K. J. Glotfelty (SAO), M. Karovska (SAO), C. S. Anderson (SAO), N. R. Bonaventura (SAO), J. C. Chen (SAO), S. M. Doe (SAO), I. N. Evans (SAO), J. D. Evans (SAO), G. Fabbiano (SAO), E. Galle (SAO), D. G. Gibbs (SAO), J. D. Grier (SAO), R. Hain (SAO), D. M. Hall (SAO), P. N. Harbo (SAO), X. He (SAO), J. Lauer (SAO), M. L. McCollough (SAO), J. C. McDowell (SAO), J. B. Miller (SAO), A. W. Mitschang (SAO), D. L. Morgan (SAO), J. S. Nichols (SAO), D. A. Plummer (SAO), B. L. Refsdal (SAO), A. H. Rots (SAO), A. L. Siemiginowska (SAO), B. A. Sundheim (SAO), M. S. Tibbetts (SAO), D. W. Van Stone (SAO), S. L. Winkelman (SAO), P. Zografou (SAO)

The Chandra Source Catalog (CSC) will ultimately contain more than ~250000 x-ray sources in a total area of ~1% of the entire sky, using data from ~10000 separate ACIS and HRC observations of a multitude of different types of x-ray sources (see Evans et al. this conference). In order to maximize the scientific benefit of such a large, heterogeneous dataset, careful characterization of the statistical properties of the catalog, i.e., completeness, sensitivity, false source rate, and accuracy of source properties, is required. Our Characterization efforts include both extensive simulations of blank-sky and point source datasets, and detailed comparisons of CSC results with those of other x-ray and optical catalogs. We present here a summary of our characterization results for CSC Release 1 and preliminary plans for future releases. This work is supported by NASA contract NAS8-03060 (CXC).

The Chandra Source Catalog: Source Properties and Data Products

Arnold Rots, SAO
Ian N. Evans (SAO), Kenny J. Glotfelty (SAO), Francis A. Primini (SAO), Panagoula Zografou (SAO), Craig S. Anderson (SAO), Nina R. Bonaventura (SAO), Judy C. Chen (SAO), John E. Davis (MIT), Stephen M. Doe (SAO), Janet D. Evans (SAO), Giuseppina Fabbiano (SAO), Elizabeth Galle (SAO), Danny G. Gibbs II (SAO), John D. Grier (SAO), Roger Hain (SAO), Diane M. Hall (NGIS), Peter N. Harbo (SAO), Xiangqun (Helen) He (SAO), John C. Houck (MIT), Margarita Karovska (SAO), Vinay L. Kashyap (SAO), Jennifer Lauer (SAO), Michael L. McCollough (SAO), Jonathan C. McDowell (SAO), Joseph B. Miller (SAO), Arik W. Mitschang (SAO), Douglas L. Morgan (SAO), Amy E. Mossman (SAO), Joy S. Nichols (SAO), Michael A. Nowak (MIT), David A. Plummer (SAO), Brian L. Refsdal (SAO), Aneta L. Siemiginowska (SAO), Beth A. Sundheim (SAO), Michael S. Tibbetts (SAO), David W. Van Stone (SAO), Sherry L. Winkelman (SAO),

The Chandra Source Catalog (CSC) is breaking new ground in several areas. There are two aspects that are of particular interest to the users: its evolution and its contents. The CSC will be a living catalog that becomes richer, bigger, and better in time while still remembering its state at each point in time. This means that users will be able to take full advantage of new additions to the catalog, while retaining the ability to back-track and return to what was extracted in the past. The CSC sheds the limitations of flat-table catalogs. Its sources will be characterized by a large number of properties, as usual, but each source will also be associated with its own specific data products, allowing users to perform mini custom analysis on the sources. Source properties fall in the spatial (position, extent), photometric (fluxes, count rates), spectral (hardness ratios, standard spectral fits), and temporal (variability probabilities) domains, and are all accompanied by error estimates. Data products cover the same coordinate space and include event lists, images, spectra, and light curves. In addition, the catalog contains data products covering complete observations: event lists, background images, exposure maps, etc. This work is supported by NASA contract NAS8-03060 (CXC).

The CSC-SDSS Cross-match Catalog

Arnold Rots, SAO
Tamas Budavari (JHU), Alex Szalay (JHU), Joan Hagler (SAO)

We have cross-matched the Chandra Source Catalog (CSC) with the Sloan Digital Sky Survey (SDSS) DR-7 source catalog using a cross-matching algorithm developed by one of us (TB) and previously applied to a cross-match of SDSS with GALEX catalogs. It is a Bayesian method that takes into account the positions, position errors, as well as the detailed footprints of the catalogs, and provides a Bayesian Factor and an associated probablity for each match. Various tests indicate that cross-matches with probabilities >0.5 are solid and can be trusted; below that value the number of multiple matches increases rapidly. 9020 CSC sources are matched with sources that SDSS considers stars, 7852 with sources considered galaxies. Approximately 150 of these CSC sources appear in both categories. The total area of the footprint intersections is 132.86 square degrees, approximately 45% of the CSC coverage. Both projects, CXC and SDSS, will provide user access to the cross-match database.We shall present details of the cross-match, an interface to it, and some initial statistical science results. This work is supported by NASA contract NAS8-03060 (CXC) and the Sloan Digital Sky Survey Collaboration.

The Chandra Source Catalog: Storage and Interfaces

David Van Stone, SAO
David W. Van Stone (SAO), Peter N. Harbo (SAO), Michael S. Tibbetts (SAO), Panagoula Zografou (SAO), Ian N. Evans (SAO), Francis A. Primini (SAO), Kenny J. Glotfelty (SAO), Craig S. Anderson (SAO), Nina R. Bonaventura (SAO), Judy C. Chen (SAO), John E. Davis (MIT), Stephen M. Doe (SAO), Janet D. Evans (SAO), Giuseppina Fabbiano (SAO), Elizabeth Galle (SAO), Danny G. Gibbs II (SAO), John D. Grier (SAO), Roger Hain (SAO), Diane M. Hall (NGIS), Xiangqun (Helen) He (SAO), John C. Houck (MIT), Margarita Karovska (SAO), Vinay L. Kashyap (SAO), Jennifer Lauer (SAO), Michael L. McCollough (SAO), Jonathan C. McDowell (SAO), Joseph B. Miller (SAO), Arik W. Mitschang (SAO), Douglas L. Morgan (SAO), Amy E. Mossman (SAO), Joy S. Nichols (SAO), Michael A. Nowak (MIT), David A. Plummer (SAO), Brian L. Refsdal (SAO), Arnold H. Rots (SAO), Aneta L. Siemiginowska (SAO), Beth A. Sundheim (SAO), Sherry L. Winkelman (SAO)

The Chandra Source Catalog (CSC) is part of the Chandra Data Archive (CDA) at the Chandra X-ray Center. The catalog contains source properties and associated data objects such as images, spectra, and lightcurves. The source properties are stored in relational databases and the data objects are stored in files with their metadata stored in databases. The CDA supports different versions of the catalog: multiple fixed release versions and a live database version. There are several interfaces to the catalog: CSCview, a graphical interface for building and submitting queries and for retrieving data objects; a command-line interface for property and source searches using ADQL; and VO-compliant services discoverable though the VO registry. This poster describes the structure of the catalog and provides an overview of the interfaces.