# AllWISE catalogue The following is a description of the production of the version 1.x of the catalog, that are based on the AllWise catalogs. ## Original catalog and local copy We use a local copy of the AllWise catalog downloaded from http://irsadist.ipac.caltech.edu/wise-allwise/ . The catalog has been indexed locally, using a nside=256 nested healpix scheme, allowing for fast queries by position. The indexing method is as follow: for each source position in the original catalog, its pixel id is computed, and a copy of the original catalog is created where all sources belonging to the same pixel id are written continuously. The use of a nested scheme allows for sources closely in the sky to be written in closeby positions in the file. With nside=256, the healpix size are of the order of 0.25 sq degree. ## Catalog Query For each field, the indexed catalog is queried in the following manner: - The healpix pixel ids in the catalog scheme of all the non null pixels in the master mask file of the field are computed. The master masks were obtained from [SPIRE Coverage Maps](http://fp7census.pbworks.com/w/page/87735187/SPIRE%20Coverage%20Maps). - The corresponding sources are extracted from the indexed catalog - Their position in the mask is computed - Only the sources where the mask is non null are kept. ## Catalog HELP formatting The indexed catalog contains the columns listed in http://wise2.ipac.caltech.edu/docs/release/allwise/expsup/sec2_1a.html For the HELP version, the following filters are used: WISE_W1, WISE_W2, WISE_W3, WISE_W4. In the following, the letter 'x' stands for 1, 2, 3, or 4 according to the band. The AllWise catalog provides a very large amount of information: there are 298 columns in the catalog, reporting various flags and types of photometry. Among these, there is: - wxmpro : point source profile fitting photometry - wxflux : raw flux from profile fitting photometry - wxmag : aperture corrected photometry from a 8.25" aperture measurement. - wxmag_n : aperture photometry in aperture n where n runs from 1 to 8, from 5.5" to 49.5" - wxmagp : profile fitting photometry on individual images. useful for source variability - wxgmag : magnitude of extended source in the aperture from the 2MASS XSC. On top of these, a source can be detected in band and not in others. This is indicated in the AllWise catalog by the 'det_bit' and the 'ph_qual' flags. A det_bit set to 0 indicates that the SNR at that position in the band is below 2. Two cases can As the goal of HELP is to provide a master flux for each source, we have decided to build the F_WISE_Wx values from a combination of some of the fluxes listed above: - if the source is point-like, F_WISE_Wx is computed from wxmpro. As indicator of point-like source, we used the 'ext_flg' column, requesting a value of 0. - if the source shows indications of not being point-like (ext_flg != 0), if the source has a valid wxgmag magnitude, that one is used for computing F_WISE_Wx - if the source shows indications of not being point-like (ext_flg != 0), if the source has not a valid wxgmag, the profile fitting magnitude is used (wxmpro), as there is not really other measurements that could be used without a detailed investigation. - we create a flag 'type_phot' indicating whether the source flux comes from wxmmpro (1) or wxgmag (2) **As a result, sources for which 'ext_flg' !=0 and type_phot = 1 should be treated with caution.** If a source is not detected in the band (below 2 sigma), the 'wxmpro' will contain the 95% upper limit if the pht_qual flag is 'U'. If it is 'X' or 'Z', there are no good sources of photometry and a NaN is unavoidable. To summarize, we create the following variables: - F_WISE_Wx - FErr_WISE_Wx - Detection_WISE_Wx - TypePhot_WISE_Wx that are filled according to the prescriptions in the following table: | | | | FErr_WISE_Wx | Detection_WISE_Wx | TypePhot_WISE_Wx | |--------|----------------------------------------------------------------|-----------------------------|---------------------|-------------------|------------------| | case 1 | det_bit = 1
ph_qual= 'A' or 'B' or 'C'
ext_flg = 0
| wxmpro | wxsigmpro | 1 | 1 | | case 2 | det_bit = 0
ph_qual = 'U'
ext_flg = 0 | 95 % upper limit
wxmpro | wxsigmpro (NaN) | 3 | 1 | | case 3 | det_bit = 0
ph_qual = 'X' or 'Z'
any ext_flag | wxmag (NaN) | wxsigm (NaN) | 0 | 3 | | case 4 | det_bit = 1
ext_flg > 0
wxgmag not NaN | wxgmag | w1gerr | 1 | 2 | | case 5 | det_bit = 1
ext_flg > 0
wxgmag = NaN | wxmpro | wxsigmpro | 1 | 1 | | case 6 | det_bit = 0
ext_flg > 0
ph_qual = 'u' | wxmag | wxsigm (can be NaN) | 3 | 3 | AllWise magnitudes are on the Vega scale. They are converted to the AB scale following the prescriptions of the explanatory supplement http://wise2.ipac.caltech.edu/docs/release/allsky/expsup/sec4_4h.html#conv2flux $m_{AB} = m_{Vega} + dm$ with $dm$ values of: | Band | W1 | W2 | W3 | W4 | |------|-------|-------|-------|-------| | dm | 2.699 | 3.339 | 5.174 | 6.620 | The fluxes in Jy are then computed with F_WISE_Wx = 3631. x $10^{-0.4*(mv + dm)}$. And the errors with: FErr_WISE_Wx = ln(10) / 2.5 × F_WISE_x × errmag ## Catalogs columns | Column Name | Description | |-------------------|-------------------------------------------------------------------------------------------------------------------| | srcname | Catalog official name. Full designation. | | RA | Right Ascension (J2000) in degree | | Dec | Declination (J2000) in degree | | F_WISE_W1 | Flux in the W1 band (microJy) | | FErr_WISE_W1 | Error in Flux in the W1 band (microJy) | | Detection_WISE_W1 | Flag 1/0 indicating whether the source could be detected at least at 2 sigma in the W1 band. | | PhotType_WISE_W1 | Flag [1 2 3] giving the method used for determining the flux. See TypePhot_WISE_Wx in table above | | PhotCase_WISE_W1 | Flag [1-6] indicating which is the relevant case for the measure of the source in W1 | | F_WISE_W2 | Flux in the W2 band (microJy) | | FErr_WISE_W2 | Error in Flux in the W2 band (microJy) | | Detection_WISE_W2 | Flag 1/0 indicating whether the source could be detected at least at 2 sigma in the W2 band. | | PhotType_WISE_W2 | "Flag [1 2 3] giving the method used for determining the flux. See TypePhot_WISE_Wx in table above" | | PhotCase_WISE_W2 | Flag [1-6] indicating which is the relevant case for the measure of the source in W2 | | F_WISE_W3 | Flux in the W3 band (microJy) | | FErr_WISE_W3 | Error in Flux in the W3 band (microJy) | | Detection_WISE_W3 | Flag 1/0 indicating whether the source could be detected at least at 2 sigma in the W3 band. | | PhotType_WISE_W3 | Flag [1 2 3] giving the method used for determining the flux. See TypePhot_WISE_Wx in table above | | PhotCase_WISE_W3 | Flag [1-6] indicating which is the relevant case for the measure of the source in W3 | | F_WISE_W4 | Flux in the W4 band (microJy) | | FErr_WISE_W4 | Error in Flux in the W4 band (microJy) | | Detection_WISE_W4 | Flag 1/0 indicating whether the source could be detected at least at 2 sigma in the W4 band. | | PhotType_WISE_W4 | Flag [1 2 3] giving the method used for determining the flux. See TypePhot_WISE_Wx in table above | | PhotCase_WISE_W4 | Flag [1-6] indicating which is the relevant case for the measure of the source in W4 | | cc_flags | Contamination and confusion flag. Copied from the AllWise catalog. See AllWise explanatory supplement for details | | ext_flg | Extended source flag. Copied from the AllWise catalog. See AllWise explanatory supplement for details | | var_flg | Variability flag. Copied from the AllWise catalog. See AllWise explanatory supplement for details | | ph_qual | Photometry quality flag. Copied from the AllWise catalog. See AllWise explanatory supplement for details | | cntr | Unique identification number for this object in the AllWISE Catalog/Reject Tab. Copied from the AllWise catalog. | | tmass_key | 2MASS PSC association. Copied from the AllWise catalog. See AllWise explanatory supplement for details | # Filtering (added 17th June 2018, Seb Oliver) subsets of the Allwise catalogue are created for stacking purposes using the code make_wise_samples_for_stacking.csh