# Legacy Survey Files

Top level directory for web access:

https://portal.nersc.gov/cfs/cosmo/data/legacysurvey/dr3/

Top level directory for web access to dr3.1 sweeps (see known issues for a description of dr3.1):

https://portal.nersc.gov/cfs/cosmo/data/legacysurvey/dr3/sweep/3.1/

Top level directory local to NERSC computers (for collaborators):

/global/cfs/cdirs/cosmo/data/legacysurvey/dr3/

Top level directory local to NERSC computers for dr3.1 sweeps (see known issues for a description of dr3.1):

/global/cfs/cdirs/cosmo/data/legacysurvey/dr3/sweep/3.1/

## Summary Files

### survey-bricks.fits.gz

FITS binary table with the RA, DEC bounds of each geometrical "brick" on the sky. This includes all bricks on the sky, not just the ones in our footprint or with coverage in DR3. For that information, see the next file description.

• HDU1 (only HDU) - tags in the survey-bricks.fits.gz file

Column

Type

Description

brickname

char[8]

Name of the brick.

brickid

int32

A unique integer with 1-to-1 mapping to brickname.

brickq

int16

A "priority" factor used for processing.

brickrow

int32

Dec row number.

brickcol

int32

Number of the brick within a Dec row.

ra

double

RA of the center of the brick.

dec

double

Dec of the center of the brick.

ra1

double

Lower RA boundary.

ra2

double

Upper RA boundary.

dec1

double

Lower Dec boundary.

dec2

double

Upper Dec boundary.

### survey-bricks-dr3.fits.gz

A FITS binary table with information that summarizes the contents of each brick, as of DR3.

Column

Type

Description

brickname

char[8]

Name of the brick.

ra

double

RA of the center of the brick.

dec

double

Dec of the center of the brick.

nexp_g

int16

Median number of exposures in the unique area (i.e. BRICK_PRIMARY area) of the brick in $g$-band.

nexp_r

int16

Median number of exposures in the unique area of the brick in $r$-band.

nexp_z

int16

Median number of exposures in the unique area of the brick in $z$-band.

nexphist_g

int32[6]

Histogram of number of pixels in the unique brick area with 0, 1, 2, 3, 4, or > 5 exposures in $g$

nexphist_r

int32[6]

Histogram of number of pixels in the unique brick area with 0, 1, 2, 3, 4, or > 5 exposures in $r$

nexphist_z

int32[6]

Histogram of number of pixels in the unique brick area with 0, 1, 2, 3, 4, or > 5 exposures in $z$

nobjs

int16

Total number of BRICK_PRIMARY objects in this brick, of all types.

npsf

int16

Total number of BRICK_PRIMARY objects in this brick, of type PSF.

nsimp

int16

Total number of BRICK_PRIMARY objects in this brick, of type SIMP.

nexp

int16

Total number of BRICK_PRIMARY objects in this brick, of type EXP.

ndev

int16

Total number of BRICK_PRIMARY objects in this brick, of type DEV.

ncomp

int16

Total number of BRICK_PRIMARY objects in this brick, of type COMP.

psfsize_g

float32

Median PSF size, in arcsec, evaluated at the BRICK_PRIMARY objects in this brick in $g$-band.

psfsize_r

float32

Median PSF size, in arcsec, evaluated at the BRICK_PRIMARY objects in this brick in $r$-band.

psfsize_z

float32

Median PSF size, in arcsec, evaluated at the BRICK_PRIMARY objects in this brick in $z$-band.

ebv

float32

Median SFD dust map E(B-V) extinction, in magnitudes, evaluated at BRICK_PRIMARY objects in this brick.

trans_g

float32

Median Milky Way dust transparency in $g$-band, based on ebv. See also DECAM_MW_TRANSMISSION.

trans_r

float32

Median Milky Way dust transparency in $r$-band, based on ebv. See also DECAM_MW_TRANSMISSION.

trans_z

float32

Median Milky Way dust transparency in $z$-band, based on ebv. See also DECAM_MW_TRANSMISSION.

Note that, for the nexphist rows, pixels that are masked by the NOIRLab Community Pipeline as, e.g., cosmic rays or saturation, do NOT count toward the number of exposures. More information about the morphological types and DECAM_MW_TRANSMISSION can be found on the catalogs page.

### survey-ccds-decals.fits.gz

A FITS binary table with almanac information (e.g. seeing, etc.) about each individual CCD image.

This file contains information regarding the photometric and astrometric zero points for each CCD of every DECam image that is part of the DECaLS DR3 data release. Photometric zero points for each CCD are computed by identifying stars and comparing their instrumental magnitudes (measured in an approximately 7 arcsec diameter aperture) to color-selected stars in the PanSTARRS "qz" catalog.

The photometric zeropoints (zpt, ccdzpt, etc) are magnitude-like numbers (e.g. 25.04), and indicate the magnitude of a source that would contribute one count per second to the image. For example, in an image with zeropoint of 25.04 and exposure time of 30 seconds, a source of magnitude 22.5 would contribute $30 * 10^{((25.04 - 22.5) / 2.5)} = 311.3$ counts.

Column

Type

Description

object

char[35]

Name listed in the object tag from the CCD header. For propid 2014B-0404, in most cases, this has the form: DECaLS_<tile_number>_<filter>, but this can differ for older and non-DECaLS data.

expnum

int32

Unique DECam exposure number, eg 348224.

exptime

float

Exposure time in seconds, eg 30.

filter

char[1]

Filter used for observation, eg "g", "r", "z".

seeing

float

Seeing in arcseconds determined by fitting a 2-dimensional gaussian to the median PSF of stars on the CCD, eg 1.1019.

date_obs

char[10]

Date of observation start, eg "2014-08-15". Can be combined with ut, or use mjd_obs instead.

mjd_obs

double

Date of observation in MJD (in UTC system), eg 56884.99373389.

ut

char[15]

Time of observation start, eg "23:50:58.608241".

ha

char[13]

Hour angle of the observation (HH:MM:SS)

airmass

float

Airmass, eg 1.35.

propid

char[10]

Proposal ID of the program that took this image, eg "2014B-0404".

zpt

float

Median zero point for the entire image (median of all CCDs of the image), eg 25.0927.

avsky

float

Average sky level in this image, in ADU, eg 36.9324. avsky is detailed more here

arawgain

float

Average gain for this CCD, eg 4.34.

fwhm

float

crpix1

float

Astrometric header value: X reference pixel.

crpix2

float

Astrometric header value: Y reference pixel.

crval1

double

Astrometric header value: RA of reference pixel.

crval2

double

Astrometric header value: Dec of reference pixel.

cd1_1

float

cd1_2

float

cd2_1

float

cd2_2

float

ccdnum

int16

CCD number (see DECam layout), eg 1.

ccdname

char[3]

CCD name (see DECam layout), eg "N10", "S7".

ccdzpt

float

Zeropoint for the CCD (AB mag).

ccdzpta

float

Zeropoint for amp A (AB mag).

ccdzptb

float

Zeropoint for amp B (AB mag).

ccdphoff

float

(ignore)

ccdphrms

float

Photometric rms for the CCD (in mag).

ccdskyrms

float

Sky rms (in counts)

ccdskymag

float

Mean sky background in AB mag/arcsec2 on each CCD; measured from the CP-processed frames as -2.5*alog10(ccdskycounts/pixscale/pixscale/exptime) + ccdzpt

ccdskycounts

float

Mean sky count level per pixel in the CP-processed frames measured (with iterative rejection) for each CCD in the image section [500:1500,1500:2500]

ccdraoff

float

Median astrometric offset for the CCD <PS1-DECaLS> in arcsec.

ccddecoff

float

Median astrometric offset for the CCD <PS1-DECaLS> in arcsec

ccdtransp

float

(ignore)

ccdnstar

int16

Number of stars found on the CCD.

ccdnmatch

int16

Number of stars matched to PS1 (and used to compute the photometric zero points and astrometric offsets).

ccdnmatcha

int16

Number of stars in amp A matched.

ccdnmatchb

int16

Number of stars in amp B matched.

ccdmdncol

float

Median (g-i) color from the PS1 catalog of the matched stars.

temp

float

Outside temperature in oC listed in the OUTTEMP tag in the CCD image header.

camera

char[5]

The camera that took this image; "decam".

expid

char[12]

Exposure ID string, eg "00348224-S29" (from expnum and ccdname)

image_hdu

int16

FITS HDU number in the image_filename file where this image can be found.

image_filename

char[61]

Path to FITS image, eg "decam/CP20140810_g_v2/c4d_140815_235218_ooi_g_v2.fits.fz".

width

int16

Width in pixels of this image, eg 2046.

height

int16

Height in pixels of this image, eg 4096.

ra_bore

double

Telescope boresight RA of this exposure (deg).

dec_bore

double

Telescope boresight Dec of this exposure (deg).

ra

double

Approximate RA center of this CCD (deg).

dec

double

Approximate Dec center of this CCD (deg).

### survey-ccds-nondecals.fits.gz

As for survey-ccds-decals.fits.gz, but for areas of the sky covered with DECam by surveys other than DECaLS.

### survey-ccds-extra.fits.gz

As for survey-ccds-nondecals.fits.gz but for some additional regions of the sky. The "nondecals" and "extra" files are currently split up simply to make them easier to store on github.

### ccds-annotated-decals.fits.gz

A version of the survey-ccds-decals.fits.gz file with additional information gathered during calibration pre-processing before running the Tractor reductions.

Includes everything listed in the survey-ccds-decals.fits.gz files plus the following:

Column

Type

Description

photometric

boolean

True if this CCD was considered photometric and used in the DR3 reductions

blacklist_ok

boolean

We blacklisted certain programs (Proposal IDs) from other PIs where there were a large number of images covering a single patch of sky, because our pipeline code didn't handle the extreme depth very well. True if this CCD was not blacklisted, ie, was used.

good_region

int[4]

If only a subset of the CCD images was used, this array of x0,x1,y0,y1 values gives the coordinates that were used, [x0,x1), [y0,y1). -1 for no cut (most CCDs).

ra0

double

RA coordinate of pixel (1,1)

dec0

double

Dec coordinate of pixel (1,1)

ra1

double

RA coordinate of pixel (1,H)

dec1

double

Dec coordinate of pixel (1,H)

ra2

double

RA coordinate of pixel (W,H)

dec2

double

Dec coordinate of pixel (W,H)

ra3

double

RA coordinate of pixel (W,1)

dec3

double

Dec coordinate of pixel (W,1)

dra

float

Maximum distance from RA,Dec center to the edge midpoints, in RA

ddec

float

Maximum distance from RA,Dec center to the edge midpoints, in Dec

ra_center

double

RA coordinate of CCD center

dec_center

double

Dec coordinate of CCD center

sig1

float

Median per-pixel error standard deviation, in nanomaggies.

meansky

float

Our pipeline (not the CP) estimate of the sky level, average over the image, in ADU.

stdsky

float

Standard deviation of our sky level

maxsky

float

Max of our sky level

minsky

float

Min of our sky level

pixscale_mean

float

Pixel scale (via sqrt of area of a 10x10 pixel patch evaluated in a 5x5 grid across the image), in arcsec/pixel.

pixscale_std

float

Standard deviation of pixel scale

pixscale_max

float

Max of pixel scale

pixscale_min

float

Min of pixel scale

psfnorm_mean

float

PSF norm = 1/sqrt of N_eff = sqrt(sum(psf_i^2)) for normalized PSF pixels i; mean of the PSF model evaluated on a 5x5 grid of points across the image. Point-source detection standard deviation is sig1 / psfnorm.

psfnorm_std

float

Standard deviation of PSF norm

galnorm_mean

float

Norm of the PSF model convolved by a 0.45" exponential galaxy.

galnorm_std

float

Standard deviation of galaxy norm.

psf_mx2

float

PSF model second moment in x (pixels^2)

psf_my2

float

PSF model second moment in y (pixels^2)

psf_mxy

float

PSF model second moment in x-y (pixels^2)

psf_a

float

PSF model major axis (pixels)

psf_b

float

PSF model minor axis (pixels)

psf_theta

float

PSF position angle (deg)

psf_ell

float

PSF ellipticity 1 - minor/major

humidity

float

Percent humidity outside

outtemp

float

Outside temperate (deg C).

tileid

int32

DECaLS tile number, if this was a DECaLS observation; or 0 for data from other programs.

tilepass

uint8

DECaLS tile pass number, 1, 2 or 3, if this was a DECaLS observation, or 0 for data from other programs. Set by the observers; pass 1 is supposed to be photometric with good seeing, pass 3 unphotometric or bad seeing, and pass 2 in between.

tileebv

float

Mean SFD E(B-V) extinction in the DECaLS tile, or 0 for non-DECaLS data.

plver

char[6]

Community Pipeline (CP) PLVER version string

ebv

float

SFD E(B-V) extinction for CCD center

decam_extinction

float[6]

Extinction for DECam filters ugrizY

wise_extinction

float[4]

Extinction for WISE bands W1,W2,W3,W4

psfdepth

float

5-sigma PSF detection depth in AB mag, using PsfEx PSF model

galdepth

float

5-sigma galaxy (0.45" round exp) detection depth in AB mag

gausspsfdepth

float

5-sigma PSF detection depth in AB mag, using Gaussian PSF approximation (using seeing value)

gaussgaldepth

float

5-sigma galaxy detection depth in AB mag, using Gaussian PSF approximation

### ccds-annotated-nondecals.fits.gz

As for ccds-annotated-decals.fits.gz, but for areas of the sky covered with DECam by surveys other than DECaLS.

### ccds-annotated-extra.fits.gz

As for ccds-annotated-nondecals.fits.gz but for some additional regions of the sky. The "nondecals" and "extra" ccds files are currently split up simply to make them easier to store on github.

### dr3-depth.fits.gz

A concatenation of the depth histograms for each brick, from the coadd/*/*/*-depth.fits tables. These histograms describe the number of pixels in each brick with a 5-sigma AB depth in the given magnitude bin.

### dr3-depth-summary.fits.gz

A summary of the depth histogram of the whole DR3 survey. FITS table with the following columns:

Column

Type

Description

depthlo

float

Lower limit of the depth bin

depthhi

float

Upper limit of the depth bin

counts_ptsrc_g

int

Number of pixels in histogram for point source depth in g band

counts_gal_g

int

Number of pixels in histogram for canonical galaxy depth in g band

counts_ptsrc_r

int

Number of pixels in histogram for point source depth in r band

counts_gal_r

int

Number of pixels in histogram for canonical galaxy depth in r band

counts_ptsrc_z

int

Number of pixels in histogram for point source depth in z band

counts_gal_z

int

Number of pixels in histogram for canonical galaxy depth in z band

The depth histogram goes from magnitude of 20.1 to 24.9 in steps of 0.1 mag. The first and last bins are "catch-all" bins: 0 to 20.1 and 24.9 to 100, respectively. The histograms count the number of pixels in each brick's unique area with the given depth. These numbers can be turned into values in square degrees using the brick pixel area of 0.262 arcseconds square. These depth estimates take into account the small-scale masking (cosmic rays, edges, saturated pixels) and detailed PSF model.

## External Files

The DECaLS photometric catalogs have been matched to the following external spectroscopic files from the SDSS, which can be accessed through the web at:

https://portal.nersc.gov/cfs/cosmo/data/legacysurvey/dr3/external/

Or on the NERSC computers (for collaborators) at:

/global/cfs/cdirs/cosmo/data/legacysurvey/dr3/external/

Each row of each external-match file contains the full record of the nearest object in our Tractored survey imaging catalogs, matched at a radius of 1.0 arcsec. The structure of the imaging catalog files is documented on the catalogs page. If no match is found, then OBJID is set to -1.

### survey-dr3-specObj-dr13.fits

HDU1 (the only HDU) contains Tractored survey photometry that is row-by-row-matched to the SDSS DR13 spectrosopic pipeline file such that the photometric parameters in row "N" of survey-dr3-specObj-dr13.fits matches the spectroscopic parameters in row "N" of specObj-dr13.fits. The spectroscopic file is documented in the SDSS DR13 data model for specObj-dr13.fits.

### survey-dr3-DR12Q.fits

HDU1 (the only HDU) contains Tractored survey photometry that is row-by-row-matched to the SDSS DR12 visually inspected quasar catalog (Paris et al. 2017) such that the photometric parameters in row "N" of survey-dr3-DR12Q.fits matches the spectroscopic parameters in row "N" of DR12Q.fits. The spectroscopic file is documented in the SDSS DR12 data model for DR12Q.fits.

### survey-dr3-Superset_DR12Q.fits

HDU1 (the only HDU) contains Tractored survey photometry that is row-by-row-matched to the superset of all SDSS DR12 spectroscopically confirmed objects that were visually inspected as possible quasars (Paris et al. 2017) such that the photometric parameters in row "N" of survey-dr3-Superset_DR12Q.fits matches the spectroscopic parameters in row "N" of Superset_DR12Q.fits. The spectroscopic file is documented in the SDSS DR12 data model for Superset_DR12Q.fits.

### survey-dr3-DR7Q.fits

HDU1 (the only HDU) contains Tractored survey photometry that is row-by-row-matched to the SDSS DR7 visually inspected quasar catalog (Schneider et al. 2010) such that the photometric parameters in row "N" of survey-dr3-DR7Q.fits matches the spectroscopic parameters in row "N" of DR7qso.fit. The spectroscopic file is documented on the DR7 quasar catalog description page.

## Tractor Catalogs

In the file listings outlined below:

• brick names (<brick>) have the format <AAAa>c<BBB> where A, a and B are digits and c is either the letter m or p (e.g. 1126p222). The names are derived from the (RA, Dec) center of the brick. The first four digits are $int(RA \times 10)$, followed by p to denote positive Dec or m to denote negative Dec ("plus"/"minus"), followed by three digits of $int(Dec \times 10)$. For example the case 1126p222 corresponds to (RA, Dec) = (112.6°, +22.2°).

• <brickmin> and <brickmax> denote the corners of a rectangle in (RA, Dec). Explicitly, <brickmin> has the format <AAA>c<BBB> where <AAA> denotes three digits of the minimum $int(RA)$ in degrees, <BBB> denotes three digits of the minimum $int(Dec)$ in degrees, and c uses the p/m ("plus"/"minus") format outlined in the previous bullet point. The convention is similar for <brickmax> and the maximum RA and Dec. For example 000m010-010m005 would correspond to a survey region limited by $0^\circ \leq RA < 10^\circ$ and $-10^\circ \leq Dec < -5^\circ$.

• sub-directories are listed by the RA of the brick center, and sub-directory names (<AAA>) correspond to RA. For example 002 corresponds to brick centers between an RA of 2° and an RA of 3°.

• <filter> denotes the g, r or z band, using the corresponding letter.

Note that it is not possible to go from a brick name back to an exact (RA, Dec) center (the bricks are not on 0.1° grid lines). The exact brick center for a given brick name can be derived from columns in the survey-bricks.fits.gz file (i.e. brickname, ra, dec).

### tractor/<AAA>/tractor-<brick>.fits

FITS binary table containing Tractor photometry, documented on the catalogs page.

Users interested in database access to the Tractor Catalogs can contact the Astro Data Lab [1] at datalab@noirlab.edu.

## Sweep Catalogs

### sweep/3.1/sweep-<brickmin>-<brickmax>.fits

Note that previous versions of the sweeps are available in sweep/3.0/sweep-<brickmin>-<brickmax>.fits for reasons detailed on the known issues page.

The sweeps are light-weight FITS binary tables (containing a subset of the most commonly used Tractor measurements) of all the Tractor catalogs for which BRICK_PRIMARY==T in rectangles of RA, Dec. Includes:

Name

Type

Units

Description

BRICKID

int32

Brick ID [1,662174]

BRICKNAME

char

Name of brick, encoding the brick sky position, eg "1126p222" near RA=112.6, Dec=+22.2

OBJID

int32

Catalog object number within this brick; a unique identifier hash is BRICKID,OBJID; OBJID spans [0,N-1] and is contiguously enumerated within each blob

TYPE

char[4]

Morphological model: "PSF"=stellar, "SIMP"="simple galaxy" = 0.45" round EXP galaxy, "EXP"=exponential, "DEV"=deVauc, "COMP"=composite. Note that in some FITS readers, a trailing space may be appended for "PSF ", "EXP " and "DEV " since the column data type is a 4-character string

RA

float64

deg

Right ascension at equinox J2000

RA_IVAR

float32

1/deg²

Inverse variance of RA (no cosine term!), excluding astrometric calibration errors

DEC

float64

deg

Declination at equinox J2000

DEC_IVAR

float32

1/deg²

Inverse variance of DEC, excluding astrometric calibration errors

DECAM_FLUX

float32[6]

nanomaggies

DECam model flux in ugrizY

DECAM_FLUX_IVAR

float32[6]

1/nanomaggies²

Inverse variance oF DECAM_FLUX

DECAM_MW_TRANSMISSION

float32[6]

Galactic transmission in ugrizY filters in linear units [0,1]

DECAM_NOBS

uint8[6]

Number of images that contribute to the central pixel in each filter for this object (not profile-weighted)

DECAM_RCHI2

float32[6]

Profile-weighted χ² of model fit normalized by the number of pixels

DECAM_PSFSIZE

float32[6]

arcsec

Weighted average PSF FWHM per band

DECAM_FRACFLUX

float32[6]

Profile-weight fraction of the flux from other sources divided by the total flux (typically [0,1])

DECAM_FRACMASKED

float32[6]

Profile-weighted fraction of pixels masked from all observations of this object, strictly between [0,1]

DECAM_FRACIN

float32[6]

Fraction of a source's flux within the blob, near unity for real sources

DECAM_DEPTH

float32[6]

1/nanomaggies²

For a $5\sigma$ point source detection limit, $5/\sqrt(\mathrm{DECAM\_DEPTH})$ gives flux in nanomaggies and $-2.5[\log_{10}(5 / \sqrt(\mathrm{DECAM\_DEPTH})) - 9]$ gives corresponding magnitude

DECAM_GALDEPTH

float32[6]

1/nanomaggies²

As for DECAM_DEPTH but for a galaxy (0.45" exp, round) detection sensitivity

OUT_OF_BOUNDS

boolean

True for objects whose center is on the brick; less strong of a cut than BRICK_PRIMARY

DECAM_ANYMASK

int16[6]

Bitwise mask set if the central pixel from any image satisfy each condition

DECAM_ALLMASK

int16[6]

Bitwise mask set if the central pixel from all images satisfy each condition

WISE_FLUX

float32[4]

nanomaggies

WISE model flux in W1,W2,W3,W4

WISE_FLUX_IVAR

float32[4]

1/nanomaggies²

Inverse variance of WISE_FLUX

WISE_MW_TRANSMISSION

float32[4]

Galactic transmission in W1,W2,W3,W4 filters in linear units [0,1]

WISE_NOBS

int16[4]

Number of images that contribute to the central pixel in each filter for this object (not profile-weighted)

WISE_FRACFLUX

float32[4]

Profile-weight fraction of the flux from other sources divided by the total flux (typically [0,1])

WISE_RCHI2

float32[4]

Profile-weighted χ² of model fit normalized by the number of pixels

DCHISQ

float32[5]

Difference in χ² between successively more-complex model fits: PSF, SIMPle, DEV, EXP, COMP. The difference is versus no source.

FRACDEV

float32

Fraction of model in deVauc [0,1]

TYCHO2INBLOB

boolean

Is there a Tycho-2 (very bright) star in this blob?

SHAPEDEV_R

float32

arcsec

Half-light radius of deVaucouleurs model (>0)

SHAPEDEV_R_IVAR

float32

1/arcsec²

Inverse variance of SHAPEDEV_R

SHAPEDEV_E1

float32

Ellipticity component 1 (documented on the catalogs page)

SHAPEDEV_E1_IVAR

float32

Inverse variance of SHAPEDEV_E1

SHAPEDEV_E2

float32

Ellipticity component 2 (documented on the catalogs page)

SHAPEDEV_E2_IVAR

float32

Inverse variance of SHAPEDEV_E2

SHAPEEXP_R

float32

arcsec

Half-light radius of exponential model (>0)

SHAPEEXP_R_IVAR

float32

1/arcsec²

Inverse variance of R_EXP

SHAPEEXP_E1

float32

Ellipticity component 1 (documented on the catalogs page)

SHAPEEXP_E1_IVAR

float32

Inverse variance of SHAPEEXP_E1

SHAPEEXP_E2

float32

Ellipticity component 2 (documented on the catalogs page)

SHAPEEXP_E2_IVAR

float32

Inverse variance of SHAPEEXP_E2

EBV

float32

mag

Galactic extinction E(B-V) reddening from SFD98, used to compute DECAM_MW_TRANSMISSION and WISE_MW_TRANSMISSION

## Image Stacks

Image stacks are on tangent-plane (WCS TAN) projections, 3600 × 3600 pixels, at 0.262 arcseconds per pixel.

FITS binary table with the list of CCD images that were used in this brick. Same columns as survey-ccds-*.fits.gz, plus:

Column

Type

Description

ccd_x0

int16

Minimum x image coordinate overlapping this brick

ccd_x1

int16

Maximum x image coordinate overlapping this brick

ccd_y0

int16

Minimum y image coordinate overlapping this brick

ccd_y1

int16

Maximum y image coordinate overlapping this brick

brick_x0

int16

Minimum x brick image coordinate overlapped by this image

brick_x1

int16

Maximum x brick image coordinate overlapped by this image

brick_y0

int16

Minimum y brick image coordinate overlapped by this image

brick_y1

int16

Maximum y brick image coordinate overlapped by this image

psfnorm

float

Same as psfnorm in decals-ccds-annotated.fits

galnorm

float

Same as galnorm in decals-ccds-annotated.fits

plver

char[6]

Community Pipeline (CP) version

skyver

char[16]

Git version of the sky calibration code

wcsver

char[16]

Git version of the WCS calibration code

psfver

char[16]

Git version of the PSF calibration code

skyplver

char[16]

CP version of the input to sky calibration

wcsplver

char[16]

CP version of the input to WCS calibration

psfplver

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CP version of the input to PSF calibration

Stacked image centered on a brick location covering 0.25° × 0.25°. The primary HDU contains the coadded image (inverse-variance weighted coadd), in units of nanomaggies per pixel.

• NOTE: These are not the images used by Tractor, which operates on the single-epoch images.

• NOTE: that these images are resampled using Lanczos-3 resampling.

Corresponding stacked inverse variance image based on the sum of the inverse-variances of the individual input images in units of 1/(nanomaggies)² per pixel.

• NOTE: These are not the inverse variance maps used by Tractor, which operates on the single-epoch images.

Stacked model image centered on a brick location covering 0.25° × 0.25°.

• The Tractor's idea of what the coadded images should look like; the Tractor's model prediction.

Stacked χ² image, which is approximately the summed χ² values from the single-epoch images.

Stacked depth map in units of the point-source flux inverse-variance at each pixel.

• The 5σ point-source depth can be computed as 5 / sqrt(depth_ivar) .

Stacked depth map in units of the canonical galaxy flux inverse-variance at each pixel. The canonical galaxy is an exponential profile with effective radius 0.45" and round shape.

• The 5σ galaxy depth can be computed as 5 / sqrt(galdepth_ivar) .

Number of exposures contributing to each pixel of the stacked images.

JPEG image of calibrated image using the g,r,z filters as the colors.