tokens: stars increases rapidly toward fainter magnitudes. The relative fractions are a combinations of the intrinsic distribution of different types of sources, whereby the density of Galactic stars increases toward the disk of the Milky Way, while the distribution of extragalactic sources does not depend on the Milky Way structure, but all sources are affected by the Milky Way dust, which is mostly confined to a thin disk. The reddening therefore depends on the line of sight toward the sources going through more or less of the dust disk. This effect was dramatically illustrated by Figure 2 (bottom) of Bianchi et al. ( 2011a ): the “V-shape” region devoided of UV-source counts in their figure is essentially a direct image of the dust disk. It is also visible, though less evident, in Figure 6 . Figure 6. Top: number of sources per square degree detected in NUV (left) and in FUV (right), as a whole (circles) or by magnitude ranges (dots). Values are shown for every 5° latitude strip. Bottom: fraction of FUV detections over NUV detections (left), and fraction of sources with FUV–NUV 0.5 (middle), and 0.0 (right) among the FUV detections (no error cuts, but sources in the footprint of extended objects have been excluded from the counts). While the faint sources (largely extragalactic) dominate the total samples, the FUV-detected sources are mostly bright stars. We recall that, for average Galactic dust, the UV extinction is similar in FUV and NUV, and much higher in both bands than at optical wavelengths (Table 1 and Bianchi 2011 ). In Figure 6 we plot the density of NUV and of FUV sources in GUVcat_AIS (top plot) as a whole and divided by NUV magnitude ranges; the plots show that the sources fainter than NUV_mag = 21mag dominate the sample, despite AIS being the shallowest survey, and especially in the NUV, where extragalactic objects are more prominent. The bottom panels show the fraction of FUV detections over NUV detections, again as a function of Galactic latitude, and among these, the hot and very hot sources (FUV_mag-NUV_mag ≤ 0.5 and ≤0.0 respectively). Such UV color cuts correspond to different stellar for different types of stars (Bianchi 2009 ), but roughly hotter than ∼15,000 K. Some QSOs may intrude on these FUV–NUV color cuts, as shown by Bianchi et al. ( 2009 ): these affect the faint sources most. The different behavior of relative source densities in Figure 6 reflects the fact that brighter samples (and hotter samples) are dominated by Galactic stars, which are more numerous in the Milky Way disk (see, e.g., Bianchi et al. ( 2011a )). 8.2. Summary of Suggestions and Caveats for Using the Catalog To conclude, we distill here, in terms of practical advice for users, the relevant information on the catalogs presented in this paper. 1. GUVcat_AIS contains unique measurements of all sources from AIS observations with both FUV and NUV detectors exposed. Duplicate measurements are removed in the main catalog, however, a version called
ner_tags: O O O O O O O O O O O O O O O O O O O O O O O O O B-CelestialObject O O O O O O O B-CelestialObject I-CelestialObject O O O O O O O O O O O B-CelestialObject I-CelestialObject O O O O O O O O B-CelestialObject I-CelestialObject O O O O O O O B-CelestialObjectRegion I-CelestialObjectRegion O O O O O O O O O O O O O O O O O O B-CelestialObjectRegion I-CelestialObjectRegion I-CelestialObjectRegion O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O O O B-Wavelength O O O O O O O O O O B-CelestialObjectRegion I-CelestialObjectRegion I-CelestialObjectRegion O O O O O O O O O O O O O O O O O O O O O O B-Wavelength O O O B-Wavelength O O O O O O O O O O O O O O O O O O O O O B-Wavelength O O B-Wavelength O O O O O O O B-Wavelength O O O O O O O B-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O B-CelestialObject O O B-Wavelength O O O O B-Wavelength O B-Wavelength O O O O O O O O B-Wavelength O O O O B-Citation I-Citation O O O O O O O O O B-Wavelength O O B-Wavelength O O B-Dataset O O O O O O O O B-Wavelength O O O O O O O O O O B-Formula I-Formula I-Formula O O O O B-Survey O O O O O O O O B-Wavelength O O O O O O O O O O O O O B-Wavelength O O B-Wavelength O O O O O O B-CelestialObject O O O O O O O O O O B-Formula I-Formula I-Formula I-Formula I-Formula O O B-Wavelength O O O O O O O O O O O B-Citation I-Citation O O O O O O O O O O O O O B-Wavelength O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-CelestialObject O O O O O O O B-CelestialObjectRegion I-CelestialObjectRegion I-CelestialObjectRegion O O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Dataset O O O O O O O B-Telescope O O O B-Wavelength O B-Wavelength O O O O O O O O O O O O O O