DECam data already in the NOAO archive


The figures below illustrate the parts of the eROSITA-DE sky which have been already observed by DECam according to a dump of the CTIO QC database (query made by A.Zenteno on 2018-02-16). Note that it is possible that there are some DECam observations in the public NOAO science archive which do not have qc entries available in the CTIO DB. Some light data quality filtering has been applied according to the available archival parameters (AM<2.5, Texp=15s, obstype="object", Teff>0.2, FWHM<2.2arcsec). Some of these data are currently proprietary. The effective exposure time for each DECam observation is computed as "exposure*qc_teff". The figure shows which of the standard DECaLS/BLISS/DECaPS/DeROSITAS/etc tiling grid points (3*15872 tiles over the full sky, computed by D.Schlegel et al. for DECaLS) lie within 55arcmin of at least 3 DECam exposures with total effective exposure time above the indicated thresholds. The plots only show the results for "PASS==1" of the tiling pattern. This conservative choice of radius results in some extra holes beyond what we would obtain by adopting the nominal FOV of the DECam instrument (2deg diam). A more accurate picture of actual coverage can be estimated by resampling the DECam focal plane layout down onto a HEALPIx grid at the locations of each observation.

Since we do now have a good idea of the quality (i.e. IQ, transparency) of these observations, the threshold exposure time for "completeness" (Tthresh) is set to be 100% of the DeROSITAS (PI: A.Zenteno) exposure depths computed for nominal dark conditions (g=25s;r=75s;i=70s;z=90s), and is arbitrarily set to be 300s in the u band, 200s in the Y band and 300s in the VR band.

We consider sky as "Complete" when Texp>=Tthresh and Nexp>=3. Patchy sky has sufficient total exposure time, but too few exposures (Texp>=Tthresh and Nexp<3). Shallow sky has Texp < Tthresh.

Please contact dwelly --at-- if you have any questions

Annotated Tiling Files

The FITS data file containing the summary coverage info per tile is here: (decam_tiles_withqcobs*.fits.gz). It has the following format:

Column Name Format Description
1 DTILING_TILEID J ID number of this tile
2 DTILING_RA D deg, J2000
3 DTILING_DEC D deg, J2000
4 DTILING_PASS I 1, 2, or 3
5 DTILING_IN_SDSS I =1 if in SDSS footprint
6 DTILING_IN_DES I =1 if in DES footprint
7 DTILING_IN_DESI I =1 if in DESI footprint
8 DTILING_EBV_MED E mag, extinction from SFD'98
9 DTILING_NH_LAB D cm-2, from Lambda map (LAB?)
10 DTILING_NH_HI4PI D cm-2, from HI4PI map (HI4PI Collaboration+, 2016)
11 DTILING_RHO_2MASS D objects deg-2, from 2MASS
12 DTILING_RHO_GAIADR1 D objects deg-2, from Gaia-DR1
13 DTILING_IN_ERO_DE 1I =1 if in German half of eROSITA sky (180<=l<=360 deg)
14 DTILING_IN_BLISS 1I =1 if in BLISS goal footprint
15 DTILING_IN_DECaPS 1I =1 if in DECaPS goal footprint
16 DTILING_IN_MagLiteS 1I =1 if in MagLiteS goal footprint
17 DTILING_IN_VST_ATLAS 1I =1 if in nominal VST/ATLAS footprint
18 DTILING_IN_VST_KiDS 1I =1 if in nominal VST/KiDS footprint
19 DTILING_IN_HSC_WIDE 1I =1 if in nominal Subaru HyperSuprimeCam Survey-Wide footprint
20 OBS_NEXP_u 1J Number of DECam u-band exposures meeting criteria within search radius
21 OBS_TEXP_u 1E Summed effective exposure time (s) of DECam u-band exposures meeting criteria within search radius
22 OBS_NEXP_g 1J same as OBS_NEXP_u, but for g-band
23 OBS_TEXP_g 1E same as OBS_TEXP_u, but for g-band
24 OBS_NEXP_r 1J same as OBS_NEXP_u, but for r-band
25 OBS_TEXP_r 1E same as OBS_TEXP_u, but for r-band
26 OBS_NEXP_i 1J same as OBS_NEXP_u, but for i-band
27 OBS_TEXP_i 1E same as OBS_TEXP_u, but for i-band
28 OBS_NEXP_z 1J same as OBS_NEXP_u, but for z-band
29 OBS_TEXP_z 1E same as OBS_TEXP_u, but for z-band
30 OBS_NEXP_Y 1J same as OBS_NEXP_u, but for Y-band
31 OBS_TEXP_Y 1E same as OBS_TEXP_u, but for Y-band
32 OBS_NEXP_VR 1J same as OBS_NEXP_u, but for VR-band
33 OBS_TEXP_VR 1E same as OBS_TEXP_u, but for VR-band

DECam Observation List Files

Below are gzipped FITS files containing the catalogue of all observations in each filter. Columns 1-24 are those returned by the public NOAO archive server (see the schema here). Column 25 "seq_id" is derived from "dtacqnam", and colums 26-38 are from the CTIO QC database, (prefixed by "DQ_").

u-band g-band r-band i-band z-band Y-band VR-band

Sky maps

I also overlay a few relevant survey footprints: light salmon hashed area = DESI targeting region; green solid line = BOSS imaging footprint; orange solid line = BLISS footprint; blue solid line = DECaPS; red hashed area = VST-ATLAS; black dotted outline = DES. The eROSITA DE/RU boundary is indicated by a thick black dashed line, with German sky to the South. Tiles suffering from strong Galactic dust reddening, E(B-V)>0.3mag, are outlined in black, those with high stellar density (ρGaia>30000 deg-2) are shown with magenta stars, and those with large Galactic absorbing columns (NH>1021 cm-2) are shown with grey circles.

Primary science filters

g r
i z

Additional filters

u Y VR

Simplified version, with emphasis on extragalactic sky

u g r i z Y VR

Fractional coverage of the "best" part of the eROSITA-DE extragalactic sky

The following plots show the cumulative sky area coverered by existing DECam observations, as a function of the local Galactic dust redenning, E(B-V), Gaia-DR1 source density, and Galactic column density NH. Note that there are 15872 tilings in each 'PASS' over the full sky (2.6 deg2/tile), and 7936 per PASS in the eROSITA-DE part of the sky.

Primary science filters (g,r,i,z)

Filter Galactic dust redenning, E(B-V) Gaia-DR1 source density Galactic column density, NH

Additional filters (u,Y,VR)

Filter Galactic dust redenning, E(B-V) Gaia-DR1 source density Galactic column density, NH

Further useful plots

Figure Description
What sky is good for extragalactic work?
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