The WPHOT system used to process the 3-Band Cryogenic observations is, for the most part, unchanged from the All Sky Release processing. There are two instances in which the processing was different: Variability and the Extended Source Flag. Details are given below for each.
Includes the following parameters: w1dmag, w?ndf, w?mlq, w?mJDmax, w?mJDmean, rho12, rho23, q12 and q23; details to follow:
Column Name | Format | Units | nulls | Description | |
---|---|---|---|---|---|
w1dmag | %5.3f | mag | yes | Difference between maximum and minimum magnitude of the source from all usable frames, band 1. Single-frame rchi2 values greater than 3.0 times the median are rejected. | |
w1ndf | %6d | ---- | yes | Number of degrees of freedom in the flux variability chi-square, band 1. | |
w2ndf | %6d | ---- | yes | Number of degrees of freedom in the flux variability chi-square, band 2. | |
w3ndf | %6d | ---- | yes | Number of degrees of freedom in the flux variability chi-square, band 3. | |
w1mlq | %4d | ---- | yes | Probability measure that the source is variable in flux, band 1. The value is -log10(Q), where Q = 1 -P(chi2). P is the cumulative distribution probability for flux^{[1]}. The value is clipped at 9. | |
w2mlq | %4d | ---- | yes | Probability measure that the source is variable in flux, band 2. The value is -log10(Q), where Q = 1 -P(chi2). P is the cumulative distribution probability for flux^{[1]}. The value is clipped at 9. | |
w3mlq | %4d | ---- | yes | Probability measure that the source is variable in flux, band 3. The value is -log10(Q), where Q = 1 -P(chi2). P is the cumulative distribution probability for flux^{[1]}. The value is clipped at 9. | |
w?mJDmin | %17.8f | ---- | yes | The minimum modified Julian Date (mJD) of the frames containing the source. | |
w?mJDmax | %17.8f | ---- | yes | The maximum modified Julian Date (mJD) of the frames containing the source. | |
w?mJDmean | %17.8f | ---- | yes | The mean modified Julian Date (mJD) of the frames containing the source. | |
rho12 | %4d | percent | yes | The correlation coefficient between the W1 and W2 single-frame flux measurements. The value is a signed 2-digit integer, expressed as a percentage. Negative values indicate anticorrelation. | |
rho23 | %4d | percent | yes | The correlation coefficient between the W2 and W3 single-frame flux measurements. The value is a signed 2-digit integer, expressed as a percentage. Negative values indicate anticorrelation. | |
q12 | %4d | ---- | yes | Correlation significance between W1 and W2^{[2]}. The value is -log10(Q2(rho12)), 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. | |
q23 | %4d | ---- | yes | Correlation significance between W2 and W3^{[2]}. The value is -log10(Q2(rho23)), 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. | |
Notes: [1] The Q value is the fraction of all cases to be expected 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 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. [2] 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. |
Sources that are either associated with 2MASS XSC galaxies, or suspected to be resolved, are flagged as "extended." Specifically, the extended source flag indicates whether or not the morphology of a source is consistent with the WISE point spread function in any band. The flag value reflects sources that are either associated with known galaxy (e.g., 2MASS XSC) or have a poor reduced CHI^2 of the profile-fit photometry measurement (signature of resolved or source confusion nature). The flag is further delinated into the following categories:
Last update: 2012 June 25