The XMM-OM Serendipitous Ultra-violet Source Survey (SUSS) is a
catalog 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.
The catalog 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 catalog. Taking account of substantial overlaps between observations,
the net sky area covered independently is 29 - 54 square degreees, depending
on UV filter. The primary content of the catalog is filter-dependent source
positions and magnitudes, and these are accompanied by profile diagnostics
and variability statistics.
The XMM-OM SUSS catalog contains 753,578 UV source detections above a
signal-to-noise threshold limit of 3-sigma 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 of the MSSL
documentation for this catalog:
<a href="http://www.mssl.ucl.ac.uk/~mds/XMM-OM-SUSS/SourcePropertiesFilters.shtml">http://www.mssl.ucl.ac.uk/~mds/XMM-OM-SUSS/SourcePropertiesFilters.shtml</a>.
Consequently, the scope for science based on temporal source variability on
timescales of hours to years is broad.
The positional accuracy of the catalog detections is typically 1.0 arcsec
(1-sigma confidence radius) with a median positional error of 0.67 arcsec. The
median AB magnitude of the catalog 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 catalog, 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 catalog 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 full documentation.
The processing used to generate the catalog is based on the SAS8.0 pipeline
developed for the pipeline reduction of all XMM 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.
