Catalogs

• astrometry atlas

  The astrometry atlas contains the names and astrometry for each coadd composing the unWISE imaging. This is useful to see exactly which images contribute to different parts of the footprint.

• individual image catalogs

  The individual image catalogs are available for every unWISE coadd (36480 files; 18240 tiles and two bands). The tabulated fields are described below. Sizes range from 3 to 20 MB, totaling 373 GB.

  The entire individual image catalog can be downloaded via wget -I unwise/release/cat/ --reject "index.html*" -nH --recursive http://faun.rc.fas.harvard.edu/unwise/release/cat/.

• band-merged catalogs

  The band-merged catalogs are very similar to the individual-image catalogs, except most fields have been transformed into two-element vectors, corresponding to the WISE 3.4 and 4.6 micron bands. There is one file for each of the 18240 tiles. The fields are described below. Sizes range from 20 to 60 MB, totaling 541 GB.

  The entire object catalog can be downloaded via wget -I unwise/release/band-merged/ --reject "index.html*" -nH --recursive http://faun.rc.fas.harvard.edu/unwise/release/band-merged/.

crowdsource analyzes each single-band unWISE tile individually to determine the position and flux of all sources in the image. The resulting output catalog has the following fields:

The "quality factor" is a concept inherited from PS1. It tabulates the PSF-weighted fraction of pixels contributing to this detection. Good detections will have quality factors close to one. Heavily saturated detections will have quality factors close to zero.

The x and y coordinates are defined so that in Python, image[x, y] gives the value of the pixel (x, y). This means that in terms of layout in memory, the y index increases faster than the x index. This is in contrast to the usual convention, so caveat emptor.

Most columns in the unWISE band-merged catalogs are identical to the individual-image catalogs. In these cases, the columns are simply two-element vectors corresponding to the W1 and W2 measurements of a source. These columns are not documented further. A few columns are added, however, and are documented below.

All fluxes are in "Vega nMgy", so that the Vega magnitude of a source is given by \(22.5-2.5\log(\mathrm{flux})\). The absolute calibration is ultimately inherited from AllWISE through the calibration of Meisner et al. (2017). This inheritance depends on details of the PSF normalization at large radii, which is uncertain. To improve the agreement between unWISE and AllWISE fluxes, we recommend subtracting 4 mmag from unWISE W1 and 32 mmag from unWISE W2 fluxes.

Corresponding AB magnitudes are given by the following equations:

• \(m_{\mathrm{W1}, \mathrm{AB}} = m_{\mathrm{W1}, \mathrm{Vega}} + 2.699\)
• \(m_{\mathrm{W2}, \mathrm{AB}} = m_{\mathrm{W2}, \mathrm{Vega}} + 3.339\)

The unWISE flags simply give the value of the unWISE mask image for the central pixel of the unWISE catalog source, after "collapsing" the time-resolved masks into a smaller number of bits appropriate for static sources. All bits mark features of very bright stars. These flags are described in more detail here.

The unWISE info flags contain additional fields related to the crowdsource processing or unWISE coadd bright star mask. These flags are described in more detail here.