XMM-Newton Serendipitous Source Catalogue: 2XMM

    We are pleased to announce the second XMM-Newton Serendipitous Source Catalogue: 2XMM.

    2XMM is the second comprehensive catalogue of serendipitous X-ray sources from the European Space Agency's (ESA) XMM-Newton observatory. The catalogue has been constructed by the XMM-Newton Survey Science Centre (SSC) on behalf of ESA.

The 2XMM catalogue is the largest X-ray source catalogue ever produced, containing almost twice as many discrete sources as either the ROSAT survey or pointed catalogues. 2XMM complements deeper Chandra and XMM-Newton small area surveys, probing a much larger sky area. The schematic plot to the right, loosely based on Brandt & Hasinger 2005 (ARA&A 43, 827), shows the 2XMM catalogue in comparison with other X-ray surveys.

The 2XMM catalogue provides an effective dataset for generating large, well-defined samples of various types of astrophysical object, notably active galaxies (AGN), clusters of galaxies, interacting compact binaries and active stellar coronae, using the power of X-ray selection. The large sky area covered by the serendipitous survey also means that 2XMM is a rich resource for exploring the variety of the X-ray source populations and identifying rare source types.

The catalogue contains source detections drawn from 3491 XMM-Newton EPIC observations made between 2000 February 3 and 2007 March 31; all datasets were publicly available by 2007 May 01 but not all public observations are included in this catalogue. The catalogue contains 246897 X-ray source detections which relate to 191870 unique X-ray sources. About half of the observations have features that may cause spurious detections (mainly the wings of bright sources and large extended emission), and it is strongly recommended to use a filter (either per source or per observation).

Comparison of Chandra and XMM X-ray Surveys

The median flux in the total photon energy band (0.2 - 12 keV) of the catalogue detections is ~ 2.5 × 10-14 erg cm-2 s-1; in the soft energy band (0.2 - 2 keV) the median flux is ~ 5.8 × 10-15, and in the hard band (2 - 12 keV) it is ~ 1.4 × 10-14. About 20% of the sources have total fluxes below 1 × 10-14 erg cm-2 s-1.

There are 20837 detections of extended emission in the catalogue. For 38320 detections spectra and time series were automatically extracted during processing, and a χ2-variability test was applied. 2307 detections in the catalogue are considered variable at a probability of 10-5 based on the null-hypothesis that the source is constant. For ~90% of all observations the target name could be identified via Simbad or NED and their field content (with respect to serendipitous sources) could be identified.

Note: A new version (1.2) of the 2XMM catalogue was released on 15 April 2010. This version includes important corrections to two columns relating to the EPIC band 4 fluxes for detections and unique sources. Please see here for details.


The 2XMM catalogue, released on 2007 August 22th, is available in several formats:

2XMMcat_v1.2.fits FITS binary 327 MB MD5: a2f14b8461aef25bc6aa59f9cae9b431 full binary catalogue; recommended for the experienced user and in-depth studies. V1.2 (released 15 Apr 2010) contains important corrections to the EP_4_FLUX and SC_EP_4_FLUX columns (see here).
2XMMcat_v1.2.csv.gz FITS binary 242 MB MD5: 9da309477820f428460adca1ea884bef full binary catalogue; recommended for the experienced user and in-depth studies. V1.2 (released 15 Apr 2010) contains important corrections to the EP_4_FLUX and SC_EP_4_FLUX columns (see here).
2XMMcat_slim_ v1.2.fits FITS binary MB MD5: reduced binary catalogue; recommended for the experienced user and in-depth studies. V1.2 (available soon) contains important corrections to the SC_EP_4_FLUX column (see here).
2XMMcat_slim_v1.0.fits.gz FITS binary 26 MB MD5: 089a7f437998216b113b207be0d2b4f9 reduced binary catalogue, recommended for X-ray beginners and simple studies
2XMMcat_v1.0.fits.gz FITS binary 206 MB MD5: 66a70dd94ac110dc90a21c7ffb3b5d44 full binary catalogue (without traget ID table extension), recommended for the experienced user and in-depth studies
2XMMcat_v1.0.csv.gz CSV 244 MB MD5: 3c0982c107c1842efb4b330442b441a8 full ascii catalogue (without traget ID table extension)

For convenience here is a file containing a suitable SQL CREATE statement for use with a relational DBMS in order to load the data in CSV format. The CSV file has nulls represented by two successive commas, compatible with Postgres and (probably) other DBMS.

The slimline version of the 2XMM catalogue contains one row per unique source (while the the main catalogue has one row per detection) and thus has 191870 rows. There are 39 columns, essentially those containing information about the unique sources. The catalogue also contains a column with links to the LEDAS summary pages. In the case of sources with multiple detections the best detection is selected, and the summary page gives cross-links to the other detections.

Two separate files are also provided (table below) which contain key details about the observations used in the construction of the 2XMM catalogue and information about the targets of the observations. See the list of observations and the list of target identifications for descriptions of the columns in each file. Note that in version 1.1 of the catalogue these files were contained in separate extensions of the full fits catalogue

2XMM_summary.fits FITS binary 0.4 MB MD5: ea2de9023f6bb4fcefe35d9630e03c4c Summary table of observations used in the catalogue
2XMM_targets.fits FITS binary 0.5 MB MD5: 8a72a4d1031490334938ae50a9ed0e01 Summary table of the targets of observations used in the catalogue

The following Web-based user interfaces will allow filtering and searching of the catalogue (and give access to all or selected associated data products):

The SSC Catalogue Home Page (this page), XSA, and HEASARC allow download of the catalogue file in (binary) FITS.


The User Guide for the 2XMM catalogue contains details of the catalogue production process and content (last up-dated 31-Aug-2008, see the document revision history). Here are quick links to the description of the columns in the catalogue and the list of observations used to compile the catalogue, and the list of target identifications of the observations in the catalogue. Note that modified energy bands have been used for this catalogue (as well as the pre-release catalogue 2XMMp).

Nomenclature and Citation

The correct nomenclature for references to sources in the catalogue is the name starting with the '2XMM' designator, as included in the catalogue itself, followed by a colon and the detection identification number where a specific detection is referred to (rather than the source itself), that is: "2XMM Jhhmmss.sSddmmss:detid".

The production and content of the 2XMM catalogue is described in detail in "The XMM-Newton serendipitous survey. V. The second XMM-Newton serendipitous source catalogue", M. G. Watson et al., A&A 493, p. 339


The production of the XMM catalogue is a collaborative project involving the whole SSC Consortium:

The SSC team is pleased to acknowledge the contributions to the SAS software, on which the catalogue processing is based, made by ESA's Science Operations Centre staff. Significant contributions to the earlier-mission software and data-processing activities were also made by NASA Goddard Space Flight Centre HEASARC staff resident for a substantial time at the University of Leicester. The quality of the pipeline products and the catalogue itself were ensured by the dedicated and sustained efforts of the screening team: Hermann Brunner (MPE), Marcella Brusa (MPE), Maite Ceballos (IFCA), Stephanie Dupuy (CESR), Sean Farrell (CESR), Federico Fraschetti (CEA), Georg Lamer (AIP), Anja Schroeder (LUX), Mark Simpson (LUX), Giorgia Sironi (OAB, LUX), Ann-Marie Stobbart (LUX).