UCL Department of Space and Climate Physics


Sky Coverage

Figure 1 plots the distribution of XMM-OM pointings included in the catalogue. The size of the pointing symbols are not related to field-of-view but vary in hue as the detected source density increases.

Mirroring the wide variety of scientific experiments performed by XMM for it's Guest Observers, there are sub-clusters of pointings around the Galactic plane, concentrated towards the Galactic center, and the Magellanic Clouds. Between the Galactic plane and poles the pointings have a more random distribution (in a serendipitous sense) for extra-Galactic and Galactic-neighbourhood targets. The second extension of the FITS file housing the SUSS2 catalogue (SUMMARY extension) includes information about pointing.

Positions of the sources in the catalogue in Galactic coordinates.

Fig 1: The observation content of the SUSS2 catalogue mapped onto the sky in Galactic longitude and latitude. 

The following table contains an approximate measure of the total area of sky observed through each filter, assuming an average window size of 10'x10'. fobs is the fraction of observations which contain a specific filter. N src is the number of sources found with a detection significance > 3σ.

Filter Sky Coverage (deg2)Nsrc (> 3σ)   fobs (%)  
V21 1,109,225   18  
B20660,592   16  
U105  1,205,083   93  
UVW1 75 1,971,815   63  
UVM2 59354,723   49  
UVW2 36 182,042   31  

Table 1: Sky coverage statistics for each of the six XMM-OM lenticular filters included within the catalogue.

Plotting in Figure 2 the distribution of sources as a function of Galactic latitude reveals several clusters, one associated with the Galactic plane at b = 0° and the other at b = -30° associated with the Magellanic Clouds.

Histogram of filter usage with galactic latitude
Fig 2: The normalized source number content of the XMM-SUSS2 catalogue plotted as a function of Galactic latitude.