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DES Document 7811-v4

Preliminary assessment of stellar sample completeness from the Dark Energy Survey

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Adriano Pieres
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Adriano Pieres
Document Created:
19 Apr 2014, 12:22
Contents Revised:
11 Aug 2014, 13:32
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11 Aug 2014, 13:32
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09 Jul 2014, 11:40
19 May 2014, 12:31
19 Apr 2014, 12:48
Authors: Adriano Pieres (UFRGS/LIneA), Basílio Santiago (UFRGS/LIneA), Eduardo Balbinot (UFRGS/LIneA), DES-Brazil,...
We compare the DES catalogue (as reduced by DESDM) to image reductions made using DAOPHOT. We focus on five SPT-E fields, four of them containing LMC star clusters. The cluster sample consists of two sparse (no substantial overdensity from a visual inspection) and two crowded (presenting substantial visual overdensity) objects. Simple zeropoints corrections, with no colour terms, are sufficient to place the instrumental DAOPHOT magnitudes in the DES system. We use standard procedures to draw samples of point sources from both catalogues. We then quantify DESDM stellar data completeness as a function of magnitude and crowding. The DES catalogue are highly incomplete in the dense star cluster fields, in fact leading to holes in the surface density distribution of sources close to the cluster cores. We also see substantial incompleteness of DESDM stars with g > 20 in the sparse fields. We carry out the same DAOPHOT reduction and a similar comparative analysis in a more typical DES region in SPT-E, less dominated by point sources. The completeness curves as a function of magnitude preserve the same shape as in the LMC dominated regions, but for a source density 10 times smaller. We also show that galaxy contamination is affecting DESDM and DAOPHOT samples by different amounts when usual selection criteria are applied to draw a sample of stellar sources. Galaxy contamination is much more severe in the DAOPHOT sample. This account for part, but not all, of the observed DESDM incompleteness: using only stellar sources that follow the stellar locus in the (g-r) .vs. (r-i) diagram, the DESDM sample corresponds to =~ 87% of the DAOPHOT sources down to g=22 in a typical DES field.
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held from 19 May 2014 to 23 May 2014 in UIUC
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