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    • M 51 Deep Chandra ACIS X-Ray Point Source Catalog

    Metadata Updated: April 10, 2026

    The authors obtained a deep X-ray image of the nearby galaxy M 51 using the Chandra X-Ray Observatory. Here the catalog of X-ray sources detected in these observations is presented, while an overview of the properties of the point-source population is provided in the reference paper. The authors find 298 sources within the D<sub>25</sub> radii (the apparent major isophotal galactic radii measured at or reduced to the surface brightness level mu<sub>B</sub> = 25.0 B-mag per square arcsecond) of NGC 5194 and NGC 5195, of which 20% are variable, a dozen are classical transients, and another half dozen are transient-like sources. The typical number of active ultraluminous X-ray sources in any given observation is ~5, and only two of those sources persist in an ultraluminous state over the 12 years of observations. Given reasonable assumptions about the supernova remnant population, the luminosity function is well described by a power law with an index between 1.55 and 1.7, only slightly shallower than that found for populations dominated by high-mass X-ray binaries (HMXBs), which suggests that the binary population in NGC 5194 is also dominated by HMXBs. The luminosity function of NGC 5195 is more consistent with a low-mass X-ray binary dominated population. This deep study of M51 is composed of 107 ks of archival Chandra observations, to which the authors added another 745 ks of observations. The Chandra ObsIDs and parameters of all of the observations used in this study (which span from June 2000 to October 2012) are given in Table 2 of the reference paper. All of the observations were made with the ACIS-S array. The authors used the ACIS Extract software package (AE) to perform the photometry. For each source, AE extracted a source region whose size and shape were based on the local PSF, and a background region whose size and shape were based on the size of the local PSF and the location of nearby sources. Source properties were then calculated in a standard manner. Of particular importance in this analysis is the prob_no_source parameter, which is the probability that one could measure the observed count rate in the absence of a source. The authors took a source to be significant only if this parameter was < 5 x 10<sup>-6</sup>. At this probability threshold, one would expect a single spurious source per field, or roughly 1.5 spurious sources within the D<sub>25</sub> regions. As they used the same value in their analysis of M83 (Long et al. 2014, ApJS, 212, 21, the source catalog from which is available in the HEASARC database as the <a href="/W3Browse/chandra/m83cxo.html">M83CXO</a> table), the two catalogs are directly comparable. This table was created by the HEASARC in January 2017 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/827/46">CDS Catalog J/ApJ/827/46</a> files table4.dat, table5.dat and table6.dat. This is a service provided by NASA HEASARC .

    Access & Use Information

    Public: This dataset is intended for public access and use. License: See this page for license information.

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    Dates

    Metadata Created Date April 11, 2025
    Metadata Updated Date April 10, 2026

    Metadata Source

    Harvested from NASA Data.json

    Other Data Resources

    Additional Metadata

    Resource Type Dataset
    Metadata Created Date April 11, 2025
    Metadata Updated Date April 10, 2026
    Publisher High Energy Astrophysics Science Archive Research Center
    Maintainer
    Identifier ivo://nasa.heasarc/m51cxo2
    Data Last Modified 2026-04-06
    Category Astrophysics
    Public Access Level public
    Bureau Code 026:00
    Metadata Context https://project-open-data.cio.gov/v1.1/schema/catalog.jsonld
    Schema Version https://project-open-data.cio.gov/v1.1/schema
    Catalog Describedby https://project-open-data.cio.gov/v1.1/schema/catalog.json
    Harvest Object Id 40822c0f-71e5-4237-af75-a98bdae2267d
    Harvest Source Id 58f92550-7a01-4f00-b1b2-8dc953bd598f
    Harvest Source Title NASA Data.json
    Homepage URL ivo://nasa.heasarc/m51cxo2
    License https://www.usa.gov/government-works
    Program Code 026:000
    Source Datajson Identifier True
    Source Hash a6afc02b9baea899ec256f7ad851d2f0477cdf89aba1de507542c84ca565366c
    Source Schema Version 1.1

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