Data Model: dbfits

General Description

Band-merged calibrated object catalog files subdivided into 1 x 1 degree subsets for manageable downloading. The table below documents the band-merged quantities reported as part of the catalog, which are a subset of all single-detection quantities (see cat/cer datamodel). For quantities with an additional "_OK" field, the first is an average over all detections and the "_OK" field is limited to only "OK" detections. Detections are "OK" if no bad flag bits were set for the center pixel, the quality factor and RCHI2 pass a cut, and the flux uncertainty is nonzero. See the DECaPS2 release paper for these cuts and bad flag lists.

Fields that are arrays of 6 elements in one dimension are "per band" with the band ordering ugrizY. However, no u-band observations were taken during DECaPS and thus the first element in that dimension should always be zero.

The objid for DECaPS2 has no relation to the objid for objects that also appear in DECaPS1.

All fluxes are reported in "maggies" (Mgy) which are equivalent to 3631 Jy and are a convenient unit so that $-2.5 \log_{10}(flux)$ is in AB magnitudes.

Naming Convention

decam_flux_l268\.5bm4\.5\.fits, where the coordinates represent the center of the 1 x 1 degree subset of the catalog in Galactic coordinates. An "m" preceeds the number to indicate a negative.

Approximate Size

891 MB

File Type

FITS

HDU Type

BINARY TABLE

HDU Size

891 MB

Data Table

Name	Type	Unit	Description
RA	float64	degree	right ascension
DEC	float64	degree	declination
POSSTDEV	float32	arcsec	standard deviation in position of object between different detections
RA_OK	float64	degree	right ascension
DEC_OK	float64	degree	declination
POSSTDEV_OK	float32	arcsec	standard deviation in position of object between different detections
NDET	int16		total number of detections associated with object
NDET_OK	int16		total number of detections associated with object
NMAG	int16[6]		total number of detections associated with object per band
NMAG_OK	int16[6]		total number of detections associated with object per band
MEAN	float32[6]	Mgy	mean flux per band
STDEV	float32[6]	Mgy	standard deviation of flux measurements per band (can be NaN if 1 detection)
ERR	float32[6]	Mgy	average dflux (uncertainty) per band
MEDIAN	float32[6]	Mgy	median flux per band
Q25	float32[6]	Mgy	25th percentile flux
Q75	float32[6]	Mgy	75th percentile flux
NDET_CFLUX	int16		total number of detections associated with object
NDET_CFLUX_OK	int16		total number of detections associated with object
NMAG_CFLUX	int16[6]		total number of detections associated with object per band
NMAG_CFLUX_OK	int16[6]		total number of detections associated with object per band
MEAN_CFLUX	float32[6]	Mgy	mean cflux per band
STDEV_CFLUX	float32[6]	Mgy	standard deviation of cflux measurements per band (can be NaN if 1 detection)
ERR_CFLUX	float32[6]	Mgy	average dcflux (uncertainty) per band
MEDIAN_CFLUX	float32[6]	Mgy	median cflux per band
Q25_CFLUX	float32[6]	Mgy	25th percentile cflux
Q75_CFLUX	float32[6]	Mgy	75th percentile cflux
MAGLIMIT	float32[6]	AB Mag	very rough magnitude limit at which this detection would be only 5 sigma, -2.5 * log10(5 * dflux) + zeropoint
EPOCHRANGE	float64	day	MJD difference between earliest and latest detection
EPOCHRANGE_OK	float64	day	MJD difference between earliest and latest detection
EPOCHMEAN	float64	J2000	Mean MJD
EPOCHMEAN_OK	float64	J2000	Mean MJD
DNT_ALL	int32[6]		bits from CloudCovErr solutoin thrown in all (ok) detections in a given band
DQFLAGS_ALL	int64[6]		bits from DECam Community pipeline/crowdsource solution thrown in all (ok) detections in a given band
FRACFLUX_AVG	float32[6]		average fraction of flux in this object's PSF that comes from this object
RCHI2_AVG	float32[6]		average \(\chi^2\) per pixel, weighted by PSF
QF_AVG	float32[6]		average "quality factor" based on PSF-weighted fraction of pixels contributing to the detection (0 < qf <1 ranges bad < qf < good)
PRN_AVG	float32[6]		average probability of nebulosity classification at the detection location per band
PRL_AVG	float32[6]		average probability of light nebulosity classification at the detection location per band
PRR_AVG	float32[6]		average probability of regular classification at the detection location per band
PRE_AVG	float32[6]		average probability of error mode classification at the detection location per band
CCHI2_AVG	float32[6]		average \(\chi^2\) of predicted background evaluated for "good" pixels
SNR_AVG	float32[6]		average flux/dflux
DNT_ANY	int32[6]		bits from CloudCovErr solutoin thrown in any (ok) detections in a given band
DQFLAGS_ANY	int64[6]		bits from DECam Community pipeline/crowdsource solution thrown in any (ok) detections in a given band
OBJ_ID	int64		unique DECaPS2 object ID

Examples

An example dbfits band-merged calibtrated object catalogue file is linked here: decam_flux_l283.5bm4.5.fits