XMM-Newton Serendipitous Source Catalogue: 2XMMi

    We are pleased to announce the Incremental Second XMM-Newton Serendipitous Source Catalogue 2XMMi.

    2XMMi is the incremental second 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 2XMMi catalogue has about 17% new detections as compared to the 2XMM catalogue and is the largest X-ray source catalogue ever produced, containing more than twice as many discrete sources as either the ROSAT survey or pointed catalogues. 2XMMi complements deeper Chandra and XMM-Newton small area surveys, probing a much larger sky area.

The 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 2XMMi 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 4117 XMM-Newton EPIC observations made between 2000 February 3 and 2008 March 28; all datasets were publicly available by 2008 May 01 but not all public observations are included in this catalogue. The catalogue contains 289083 X-ray source detections which relate to 221012 unique X-ray sources (covering an energy interval from 0.2 keV to 12 keV). 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). 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. The following table gives an overview of the statistics of the catalogue in comparison with the 2XMM catalogue which was published in August 2007.

Note: A new version (1.1) of the 2XMMi 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.

  2XMMi 2XMM Increment
Number of observations 4117 3491 626
Number of 'clean' observations (i.e., observation class < 3) 2021 1754 267
Observing time 03-Feb-00 -- 28-Mar-08 03-Feb-00 -- 31-Mar-07 1 year
Sky coverage, taking overlaps into account 420 sq.deg 360 sq.deg 60 sq.deg
Number of detections 289083 246897 42186
Number of unique sources 221012 191870 29300
Number of extended detections 24533 20837 3696
Number of detections with time series and spectra 44621 38320 6301
Number of variable detections 2608 2307 301
Number of 'clean' detections (i.e., summary flag < 3) 233698 199371 34327

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.


The 2XMMi catalogue, released on 2008 August 20th, is available in several formats:

2XMMicat_v1.1.fits FITS binary 386 MB MD5: 88678443fac076f2361ed5959e38c2a4 full binary catalogue; recommended for the experienced user and in-depth studies. V1.1 (released 15 Apr 2010) contains important corrections to the EP_4_FLUX and SC_EP_4_FLUX columns (see here).
2XMMicat_v1.1.csv.gz CSV 308 MB MD5: 384e8daadf59373861925a374e116950 full ascii catalogue. V1.1 (released 15 Apr 2010) contains important corrections to the EP_4_FLUX and SC_EP_4_FLUX column (see here).
2XMMicat_slim_v1.1.fits FITS binary MB MD5: reduced binary catalogue. V1.1 (coming soon) contains important corrections to the SC_EP_4_FLUX columns (see here).
2XMMicat_slim_v1.0.fits.gz FITS binary 28 MB MD5: ca74c96dea290c1c4a02f6cafb8961ef reduced binary catalogue, recommended for X-ray beginners and simple studies
2XMMicat_slim_v1.0.csv.gz CSV 32 MB MD5: e7cacb932f3262cfad2e26a91ecec1c4 reduced ascii catalogue

For convenience, there are suitable SQL CREATE statements available 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 catalogue contains one row per unique source (while the the main catalogue has one row per detection) and thus has 221012 rows. There are 37 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 summary page of the best detection is selected (i.e., the detection with the largest exposure time, summed over all cameras), 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 2XMMi 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

2XMMi_summary.fits FITS binary 0.5 MB MD5: d29febe1c0468917fd0906b04ca3fa05 Summary table of observations used in the catalogue
2XMMi_targets.fits FITS binary 0.6 MB MD5: 9a005471b4ab5ff5956a3bdc571c829b 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 2XMMi catalogue contains details of the catalogue production process and content. Here are quick links to

Nomenclature and Citation

Depending on whether a source has an existing entry in the 2XMM catalogue or is new in the 2XMMi catalogue, the correct nomenclature for references to sources in the catalogue is the name starting with the '2XMM' or '2XMMi' designator respectively, as included in the IAUNAME column of 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" or "2XMMi 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 Note that there are no differences in the processing between the 2XMM and 2XMMi observations.


The production of the 2XMMi catalogue is a collaborative project involving the whole SSC Consortium: