Information on Service 'WISE All-Sky Release Catalog SCS'

For a list of all services and tables belonging to this service's resource, see Information on resource 'WISE All-Sky Release Catalog'

Overview

You can access this service using:

• scs.xml -- a standard SCS interface as defined by the IVOA to access catalog-type data; SCS clients use http://dc.zah.uni-heidelberg.de/wise/q/s/scs.xml? to access the service
• form -- an interface for web browsers through an HTML form

Citation Info

VOResource XML (that's something exclusively for VO nerds)

Note a

The tile 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 ("b" = All-Sky) * e - Cryogenic Survey Phase ("4" = All-Sky [full cryogenic]) * v - Processing version. The disambiguation string is always ab41 for Tiles in the WISE All-Sky Release products.

For example, the identifier of the 4-band Cryo Atlas Tile with center at (α,δ = 304.13896,-13.63000) is 3041m137_ab41.

Note b

The aperture measurement quality flags indicate if one or more image pixels in the measurement aperture for this band is confused with nearby objects, is contaminated by saturated or otherwise unusable pixels, or is an upper limit. The flag value is an integer that is the combination of one or more of the following values that signify different conditions:

0:	No contamination
1:	Source confusion - another source falls within the measurement aperture
2:	Presence of bad pixels in the measurement aperture
4:	Non-zero bit flag tripped (other than 2 or 18)
8:	All pixels are flagged as unusable, or the aperture flux is negative. In the former case, the aperture magnitude is "null". In the latter case, the aperture magnitude is a 95% confidence upper limit.
16:	Saturation - there are one or more saturated pixels in the measurement aperture
32:	The magnitude is a 95% confidence upper limit

Note c

The co-sigma is related to the covariance between the position errors Vαδ by the formula Vαδ = σαδ×|σαδ|. This maintains the sign information for the correlation, since σαδ may be negative. It is more natural to carry the co-sigma along with the other uncertainties instead of the covariance because the former is in the same units as the other uncertainties.

Note d

The probability measure is -log10(Q), where Q = 1 - P(χ^2). P is the cumulative chi-square distribution probability for the flux sample measured on the individual single-exposure images. The value is clipped at 9.

The Q value is the fraction of all cases to be at least as large as that observed if the null hypothesis is true. The null hypothesis is that the flux is emitted by a non-variable astrophysical object. It may be false because the object is a true variable. It may also be false because the flux measurement is corrupted by artifacts such as cosmic rays, scattered light, etc. The smaller the Q value, the more implausible the null hypothesis, i.e., the more likely it is that the flux is either variable or corrupted or both.

Note e

The extended source flag is an integer flag, the value of which indicates whether or not the morphology of a source is consistent with the WISE point spread function in any band, or whether the source is associated with or superimposed on a previously known extended object from the 2MASS Extended Source Catalog (XSC). The values of the ext_flg indicate the following conditions:

0:	The source shape is consistent with a point-source and the source is not associated with or superimposed on a 2MASS XSC source
1:	The profile-fit photometry goodness-of-fit, w?rchi2, is >3.0 in one or more bands.
2:	The source falls within the extrapolated isophotal footprint of a 2MASS XSC source.
3:	The profile-fit photometry goodness-of-fit, w?rchi2, is >3.0 in one or more bands, and The source falls within the extrapolated isophotal footprint of a 2MASS XSC source.
4:	The source position falls within 5" of a 2MASS XSC source.
5:	The profile-fit photometry goodness-of-fit, w?rchi2, is >3.0 in one or more bands, and the source position falls within 5" of a 2MASS XSC source.

CAUTION: WISE profile-fit (w?mpro) and standard aperture (w?mag) measurements are optimized for point sources and will systematically underestimate the true flux of resolved objects. If a source entry has ext_flg>0, you may wish to examine the large aperture photometry, or the elliptical aperture photometry which are measured using areas that are scaled from 2MASS XSC morphologies.

Note p

The photometric quality flag has one character per band [W1/W2/W3/W4], that provides a shorthand summary of the quality of the profile-fit photometry measurement in each band, as derived from the measurement signal-to-noise ratio.

A:	Source is detected in this band with a flux signal-to-noise ratio w?snr>10.
B:	Source is detected in this band with a flux signal-to-noise ratio 3<w?snr<10.
C:	Source is detected in this band with a flux signal-to-noise ratio 2<w?snr<3.
U:	Upper limit on magnitude. Source measurement has w?snr<2. The profile-fit magnitude w?mpro is a 95% confidence upper limit.
X:	A profile-fit measurement was not possible at this location in this band. The value of w?mpro and w?sigmpro will be "null" in this band.
Z:	A profile-fit source flux measurement was made at this location, but the flux uncertainty could not be measured. The value of w?sigmpro will be "null" in this band. The value of w?mpro will be "null" if the measured flux is negative, but will not be "null" if the flux is positive. If a non-null magnitude is presented, it should be treated as a brightness upper limit. This occurs in rare circumstances for very bright, heavily saturated sources.

Note s

The value is -log10(Q2(rho)), where Q2 is the two-tailed fraction of all cases expected to show at least this much apparent positive or negative correlation when in fact there is no correlation. The value is clipped at 9.

rho is the correlation coefficient between the single-exposure flux measurements in the two bands.

When the number of measurements is large, the significance of correlation also tends to be large even though the correlations themselves may have a small magnitude. This is a typical manifestation of statistical significance increasing as the sample size increases; eventually the significant effect can be due to small correlated errors in background estimation or even roundoff errors. These effects tend to be small but become significant when there are enough observations of them. High flux correlation significance should be taken seriously only when the magnitude of the correlation is also fairly high.

Note t

This number is formed entirely from the source_id, which is in turn formed from the coadd_id and source number src. On average, sources with cntr values close to each other are also close to each other on the sky, except at Tile boundaries.

The cntr value is formed by making the source_id into an integer, in the format: RRRRsDDDtrevIIIIII, where

RRRR:	Tile center RA in deci-degrees, truncated not rounded (e.g. RRRR=int[10*ra]), as in the coadd_id.
s:	Tile center Declination sign translated from "p" or "m" into "1" or "0", respectively.
DDD:	Tile center Declination in deci-degrees, as in the coadd_id. 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, translated where necessary into digits corresponding to the letters' places in the alphabet. t - Tile type translated into two digits, zero-filled ("a" = "01"). r - Data Release identifier translated into a single digit, since the possible values are limited to "a" through "i" ("b" = "2"). e - Cryogenic Survey Phase ("4" = All-Sky [full cryogenic]). v - Processing version. The translated disambiguation string is always 01241 for Tiles in the WISE All-Sky Data Release Catalog .
IIIIII:	six-digit, zero-filled, sequential extracted source number, src, within the Tile.

For example, a source in the Tile 3041m137_ab41, with a source_id of '3041m137_ab41-012345', has a cntr value of 3041013701241012345.

Note u

The contamination and confusion columns contain the integer equivalent of the 9-bit binary number that specifies if the respective measurement is believed to be contaminated by or a spurious detection of an image artifact. The elements of the binary array are:

S       0       0       0       O       H       0       P       D

The leftmost bit, S, differentiates whether the band-detection is believed to be a real detection contaminated by an artifact ("0") or a spurious detection of an artifact ("1"). The remaining bits are set to "1" to denote contamination by different types of artifacts according to the letters:

D:	Diffraction spike. Source may be a spurious detection of or contaminated by a diffraction spike a nearby bright star on the same image.
P:	Persistence. Source may be a spurious detection of or contaminated by a short-term latent (persistence) image left by a bright source.
H:	Halo. Source may be a spurious detection of or contaminated by the scattered light halo associated with a bright star.
O:	Optical ghost. Source may be a spurious detection of or contaminated by an optical ghost image caused by a nearby bright source on the same image.

For example, a measurement that is believed to be a spurious detection of a diffraction spike and scattered light halo has a binary bit map value of "100001001" and w1cc_map=265.

Note v

The variability flag is a four-character string, one character per band, in which the value for each band is related to the probability that the source flux measured on the individual WISE exposures was not constant with time. The probability calculation uses the standard deviation of the single exposure flux measurements, w?sigp1, as well as the band-to-band flux correlation significance, q12,q23,q34.

The probability is computed for a band only when there are at least six single-exposure measurements available that satisfy minimum quality criteria. A value of "n" in a band indicates insufficient or inadequate data to make a determination of possible variability. Values of "0" through "9" indicate increasing probabilities of variation. Values of "0" through "5" are most likely not variables. Sources with values of "6" and "7" are likely flux variables, but are the most susceptible to false-positive variability. Var_flg values greater than "7" have the highest probability of being true flux variables in a band.

CAUTION: Estimation of flux variability is unreliable for sources that are extended (ext_flg>0), and sources whose measurements are contaminated by image artifacts in a band (cc_flags[b] != '0').