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IV. AllWISE Image Atlas

IV.1. General Properties

IV.1.c. Image Metadata


IV.1.c.iii. Atlas Image Inventory Table Format

The following table contains brief descriptions of all metadata information characterizing Atlas image data. The table also contains some processing-specific information as well as image statistics derived from the atlas images.

The columns in the following table are:


Column NameFormatUnitsnullsDescription 
coadd_id %20s ---- no Atlas Tile identifier from which source was extracted. The identifier has the general form: RRRRsDDd_[trev], where
  • RRRR = Tile center RA in deci-degrees, truncated not rounded (e.g. RRRR=int[10*ra]).
  • s = Tile center Declination sign ("p"="+", "m"="-")
  • DDD = Tile center Declination in deci-degrees. For positive declinations, the tenths of a degree is truncated not rounded (e.g. DDD=int[10*dec]). For negative declinations, the tenths of a degree is always truncated leftward on the number line (e.g. DDD=ceil[10*abs(dec)].
  • [trev] = Disambiguation string.
    • t - Tile type ("a" = Atlas)
    • r - Data Release ("c" = AllWISE)
    • e - Survey Phase ("5" = AllWISE [full cryogenic + 3-Band Cryo + Post-Cryo])
    • v - Processing version.

    The disambiguation string is always ac51 for Tiles in the AllWISE Data Release products.

For example, the identifier of the AllWISE Atlas Tile with center at (α,δ = 304.13896,-13.63000) is 3041m137_ac51.

 
band %1d ---- no WISE band number for the image.  
naxis %1d ---- no Number of data axes; it is always '2' for two-dimensional images.  
naxis1 %4d pixels no Length of data axis 1 or number of columns in the image.  
naxis2 %4d pixels no Length of data axis 2 or number of rows in the image.  
wrelease %20s ---- no The version number of the WISE multiframe pipeline used for this current data release.  
crpix1 %9.1f pixel no Axis 1 reference pixel at position crval1,crval2: 0.5*(naxis1+1)  
crpix2 %9.1f pixel no Axis 2 reference pixel at position crval1,crval2: 0.5*(naxis2+1)  
crval1 %16.12f degree no Reference Right Ascension at crpix1,crpix2 for EQUINOX.  
crval2 %16.12f degree no Reference Declination at crpix1,crpix2 for EQUINOX.  
ctype1 %13s ---- no Projection type for axis 1. It is always set to use the SIN (orthographic) projection; for the definition, see Calabretta & Greisen, 2002.  
ctype2 %13s ---- no Projection type for axis 2. It is always set to use the SIN (orthographic) projection; for the definition, see Calabretta & Greisen, 2002.  
equinox %6.1f year no Equinox of the World Coordinate System (WCS).  
bunit %20s ---- no Image pixel units: Data Number (DN) for intensity and uncertainty filetypes; "effective pixels" for the coverage filetype. Image filetypes are described in section II.3.  
elon %16.12f degrees no Ecliptic longitude of the reference pixel. CAUTION: This coordinate should not be used as an astrometric reference.  
elat %16.12f degrees no Ecliptic latitude of the reference pixel. CAUTION: This coordinate should not be used as an astrometric reference.  
glon %16.12f degrees no Galactic longitude of the reference pixel. CAUTION: This coordinate should not be used as an astrometric reference.  
glat %16.12f degrees no Galactic latitude of the reference pixel. CAUTION: This coordinate should not be used as an astrometric reference.  
ra1 %16.12f degrees no Right ascension (J2000) at corner #1 (crpix1,crpix2 = -0.5,-0.5)  
dec1 %16.12f degrees no Declination (J2000) at corner #1 (crpix1,crpix2 = -0.5,-0.5)  
ra2 %16.12f degrees no Right ascension (J2000) at corner #2 (crpix1,crpix2 = naxis1+0.5,-0.5)  
dec2 %16.12f degrees no Declination (J2000) at corner #2 (crpix1,crpix2 = naxis1+0.5,-0.5)  
ra3 %16.12f degrees no Right ascension (J2000) at corner #3 (crpix1,crpix2 = naxis1+0.5,naxis2+0.5)  
dec3 %16.12f degrees no Declination (J2000) at corner #3 (crpix1,crpix2 = naxis1+0.5,naxis2+0.5)  
ra4 %16.12f degrees no Right ascension (J2000) at corner #4 (crpix1,crpix2 = -0.5,naxis2+0.5)  
dec4 %16.12f degrees no Declination (J2000) at corner #4 (crpix1,crpix2 = -0.5,naxis2+0.5)  
magzp %9.5f mag no Relative photometric zero-point magnitude for the image.  
magzpunc %8.6f mag no 1-sigma uncertainty in the photometric zero-point magnitude for the image.  
fcdate %20s datetimeZ no Date and time of the intensity image file creation, in Coordinated Universal Time (UTC).  
date_obs1 %24s datetimeZ no The date and time (UTC) of the observation for the earliest frame in the Atlas Image stack.  
mid_obs %24s datetimeZno The date and time (UTC) of the observation for the middle frame in the Atlas Image stack.  
date_obs2 %24s datetimeZ no The date and time (UTC) of the observation for the latest frame in the Atlas Image stack.  
sizex %9.6f degrees no Linear dimension of the coadd image along axis 1 (x).  
sizey %9.6f degrees no Linear dimension of the coadd image along axis 2 (y).  
pxscal1 %9.6f arcsec/pixel no Arcsec per pixel scale at the reference position of the image (crpix1,crpix2) for axis 1 (x). See cdelt1 for the degree equivalent.  
pxscal2 %9.6f arcsec/pixel no Arcsec per pixel scale at the reference position of the image (crpix1,crpix2) for axis 2 (y). See cdelt2 for the degree equivalent.  
moonrej %6d ---- no The number of single-exposure frames rejected due to moon glow when constructing the Atlas Image. See section IV.4.f.iv on moon-affected frames.  
mooninp %6d ---- no The number of single-exposure frames in the Atlas Image footprint with suspected moon-glow as determined by the moon-mask prior to any filtering by the moon-rejection algorithm. See section IV.4.f.iv on moon-affected frames.  
medint %10.3f DN no Median intensity pixel value calculated over the full Atlas Image.  
medcov %10.3f pixel no The median depth-of-coverage per pixel for the full Atlas Image footprint.  
mincov %10.3f pixel no The minimum depth of coverage of the Atlas Image.  
maxcov %10.3f pixel no The maxmimum depth of coverage of the Atlas image.  
lowcovpc1 %10.6f ---- no The percentage of the area within the Atlas Image footprint which has the depth of coverage ≤ 4 pixels. See also the cautionary note in section I.4.c.ii.  
lowcovpc2 %10.6f ---- no The percentage of the area within the Atlas Image footprint which has the depth of coverage ≤ 6 pixels.  
nomcovpc %10.6f ---- no The percentage of the area within the Atlas Image footprint which has the depth of coverage ≤ 8 pixels.  
mincovpc %10.6f ---- no The percentage of the area of the internal working image tile used for outlier-detection which has the depth of coverage ≤ 4 pixels.  
robsig %14.6f DN no The robust estimate of the spatial sigma for pixels with depth-of-coverage values within the interval: median ± 0.25. (e.g. If the median depth-of-coverage is 8.0, it uses pixels with depth-of-coverages from 7.75 to 8.25.) The sigma is computed from a trimmed standard-deviation from the mode using only the lower-tail of the intensity pixel distribution.  
pixchis1 %11.6f ---- no The ratio between the robust spatial sigma and the median uncertainty for pixels with depth-of-coverage values within the interval: median ± 0.25. (e.g. If the median depth-of-coverage is 8.0, it uses pixels with depth-of-coverages from 7.75 to 8.25.) See also section II.3.e.i.  
pixchis2 %11.6f ---- no The ratio between the robust spatial sigma and the modal uncertainty for pixels with depth-of-coverage values within the interval: median ± 0.25. (e.g. If the median depth-of-coverage is 8.0, it uses pixels with depth-of-coverages from 7.75 to 8.25.) See also section II.3.e.i.  
mednmsk %10.1f ---- no The median number of masked pixels per frame in the frames used in the Atlas Image.  
cdelt1 %21.18f degrees/pixel no Degree per pixel scale at the reference position of the image (crpix1,crpix2) for axis 1 (x). See pxscal1 for the arcsec equivalent.  
cdelt2 %21.18f degrees/pixel no Degree per pixel scale at the reference position of the image (crpix1,crpix2) for axis 2 (y). See pxscal2 for the arcsec equivalent.  
crota2 %18.13f degrees no Image twist: the position of the image positive y-axis West of North at the EQUINOX in the opposite direction of the conventional Position Angle, where position angle (P.A.) = -CROTA for J2000.  
bitmask %9d ---- no Fatal bitstring mask template used to signal rejected input frame pixels. The bits are defined here.  
numfrms %5d ---- no The final number of single-exposure frames touching the Atlas Image footprint after all filtering is performed.  
qual_coadd %2d ---- no This integer indicates the quality score value for the Tile, with values of 0 (poor quality) or 10 (high quality). All Atlas Tiles have received quality scores of 10. The value is determined by the minimum of the quality factors qc_fact, qa_fact, and qi_fact, multiplied by ten.  
qc_fact %3.1f ---- no This quality factor gauges the quality of completion. If the status value from the Multiframe pipeline was equal to 0 (indicating a problem-free completion), then qc=1.0. Otherwise, qc=0.0 because the coadd failed to complete processing. All Atlas Tiles have received qc values of 1.0.  
qi_fact %3.1f ---- no This quality factor gauges the image shape quality. It checks for potential image smearing by using the axial ratio of the PSF calculated from a subset of sources in the Tile. The value of qi is 1.0 if the axial ratio b/a > 0.60; otherwise it is 0.0. All Atlas Tiles have received qi values of 1.0.  
qa_fact %3.1f ---- no This factor gauges the astrometric quality. If the standard deviation of WISE positions with respect to the 2MASS Point Source Catalog positions is < 0.5 arcsec on each axis (or 0.71 arcsec RSS), for sources having SNR > 20 in at least one band, then qa=1.0. Otherwise, qa=0.0. All Atlas Tiles have received qa values of 1.0.  
date_imgprep %20s datetimeZ no The date and time when the data was prepared by the WISE archive software DBPREP for the archive loading, in UTC.  
load_id %5i --- no Unique integer which identifies the data load ingested into the IRSA database  
cntr %12d ---- no Unique sequential identification number for the image metadata table entry.  
x %19.16f ---- no The x value of the reference pixel in a unit sphere coordinate system (x,y,z).  
y %19.16f ---- no The y value of the reference pixel in a unit sphere coordinate system (x,y,z).  
z %19.16f ---- no The z value of the reference pixel in a unit sphere coordinate system (x,y,z).  
spt_ind %9d ---- no The HTM spatial index key.  

Last Update: 15 November 2013


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