XMM-Newton Optical Monitor Serendipitous UV Source Survey


The XMM-OM Serendipitous Ultra-violet Source Survey (XMM-SUSS) is a catalogue of UV sources detected serendipitously by the Optical Monitor (OM) on-board the European Space Agency's (ESA's) XMM-Newton observatory. It has been created at the University College London's (UCL's) Mullard Space Science Laboratory (MSSL) on behalf of ESA and is a partner resource to the 2XMM serendipitous X-ray source catalogue. A full description of the XMM-SUSS is pubilished in this paper (Page et al. 2012, MNRAS, in press).

The catalogue contains source detections drawn from 2,417 XMM-OM observations in up to three broad band UV filters made between 2000 February 24 and 2007 March 29. All datasets included were publicly available by 2007 May 01 but note that, due to screening criteria, not all public observations are included in this catalogue. Taking account of substantial overlaps between observations, the net sky area covered independently is 29−54 deg2, depending on UV filter. The primary content of the catalogue is filter-dependent source positions and magnitudes, and these are accompanied by profile diagnostics and variability statistics.

The XMM-OM SUSS catalogue contains 753,578 UV source detections above a signal-to-noise threshold limit of 3-σ which relate to 624,049 unique objects. A significant fraction of sources (12% − UVW2, 11% − UVM2, 11.% − UVW1) are visited more than once during XMM operation, and a large fraction of sources (38% − UVW2, 23% − UVM2, 22% − UVW1) are observed more than once per filter during an individual visit. UVW2, UVM2 and UVW1 refer to the filter bandpasses defined in the Source Properties: Filter Set section. Consequently, the scope for science based on temporal source variability on timescales of hours to years is broad.

The positional accuracy of the catalogue detections is typically 1.0 arcsec (1σ confidence radius) with a median positional error of 0.67 arcsec. The median AB magnitude of the catalogue detections in the three UV bands is 19.56 (UVW2), 20.23 (UVM2) and 20.69 (UVW1). 20% of sources have AB magnitudes fainter than 20.28 (UVW2), 20.97 (UVM2) and 21.54 (UVW1).

As part of quality evaluation for the catalogue, each field has been tested for astrometric accuracy and visually screened for cosmetic problems, compromising aspect anomalies, stray light, large extended sources and telemetry dropouts. Observations affected by these issues (11.2%) have been removed from the catalogue sample. Furthermore, 2% of all observations were selected at random where each source in this sample was tested for falsehood, spuriousness and accuracy of quality flagging. The results of this detailed screening are included in the following documentation.

The processing used to generate the catalogue is based on the SAS8.0 pipeline developed for the pipeline reduction of all XMM-Newton observations. This version 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 robust detection scheme for sources close to the limit of sky background, refined quality flagging and a higher success rate (90%) for refined aspect corrections.