ESA Science & Technology - Pre-release of the Second XMM-Newton Serendipitous Source Catalogue 2XMMp

The catalogue contains 153 105 X-ray source detections (above the processing likelihood threshold of 6) which relate to 123 170 unique X-ray sources, making it the largest catalogue of astronomical X-ray sources ever produced.

The catalogue contains source detections drawn from 2400 XMM-Newton EPIC observations made between 4 February 2000 and 20 April 2006; all datasets were publicly available by 31 May 2006 but not all public observations are included in this catalogue. The median flux (in the total photon energy band 0.2 - 12 keV) of the catalogue sources is ~2.4×10^-14 erg cm^-2 s^-1; ~20% have fluxes below 1.0×10^-14 erg cm^-2 s^-1. A significant number of sources, namely 46 796, have more than one detection in the catalogue. The positional accuracy of the catalogue detections is generally < 2 arcsec (68% confidence radius). The flux values from the three EPIC cameras are overall in agreement to ~2% for on-axis sources, and ~6% off-axis.

The total area of the catalogue fields is ~ 400 square degrees, but taking account of the substantial overlaps between observations, the net sky area covered independently is ~ 285 square degrees.

The 2XMMp catalogue is essentially a subset of the full 2XMM catalogue due to be released later this year. It differs from the final catalogue mainly by the exclusion of the fraction of observations (about 17%) which, upon initial visual screening, exhibit deficiencies in the automatic processing which will require full visual screening to properly flag affected source detections. In this way the overall quality of the 2XMMp catalogue is maintained at the expense of excluding these problematic observations. These observations will, of course, be included in the full 2XMM catalogue once the detailed (and time-consuming) visual screening is completed.

The processing to generate the catalogue is largely based on the pipeline developed for the re-processing of all observations to date and includes a number of significant improvements over the previous data processing system (as used by the SSC in routine processing of XMM-Newton data on behalf of ESA). These improvements include a more sensitive source detection scheme using exposures of all cameras, the detection and parameterization of extended sources and the extraction of spectra and time series for the brightest sources.

In association with the catalogue itself, various data products will also be available (including images, exposure maps, source spectra and time-series).

The catalogue file itself is currently available, in binary FITS and ASCII CSV formats, from:

• SSC Home Page, at the SSC institute, University of Leicester
  http://xmmssc-www.star.le.ac.uk/

• XMM-Newton Science Archive (XSA) web at the XMM-Newton SOC web page:
  http://xmm.esac.esa.int/external/xmm_data_acc/xsa/index.shtml

The catalogue and selected data products will shortly (early to mid August 2006) be available in several other forms and from several servers:

• XSA, at ESA's XMM-Newton SOC
  http://xmm.esac.esa.int/xsa

• LEDAS, at the SSC institute, University of Leicester
  http://www.ledas.ac.uk/

XSA and LEDAS provide a Web-based user interface allowing filtering and searching of the catalogue, and links to associated data products.