Friday.
1502.05432
The VLT survey telescope ATLAS
Shanks, Metcalfe, ... et al
The VLT Survey Telescope (VST) ATLAS is an optical ugriz survey aiming to cover ~4700 sq deg of the Southern sky to similar depths as SDSS. From reduced images and object catalogues provided by Cambridge Astronomical Surveys Unit (CASU), first find that the median seeing ranges from 0.8" FWHM in i to 1.0" in u, significantly better than the 1.2-1.5" seeing for SDSS. The 5 sigma magnitude limit for stellar sources is r_AB=22.7 and in all bands these limits are at least as faint as SDSS. SDSS and ATLAS are more equivalent for galaxy photometry except in the z band where ATLAS has significantly higher throughput. Improved the original ESO magnitude zero points by comparing m<16 star magnitudes with APASS in gri, also extrapolating into u and z, resulting in zero points accurate to ~pm0.02 mag. Finally compare star and galaxy number counts in a 250 sqdeg area with SDSS and other count data and find good agreement. ATLAS data products can be retrieved from the ESO science archive, while support for survey science analysis is provided by the OmegaCAM Science Archive (OSA), operated by the Wide-Field Astronomy Unit in Edinburgh.
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