Despite good attempts to get the UNWISE data working, the data turn out to be poorly suited to our application. We don’t need high resolution and the lack of the zero-spacing information causes a suite of problems. Thus, we should probably use ALLWISE and a cursory look at the data suggests that they are better calibrated and don’t suffer from spatial filtering.

ALLWISE on left, UNWISE on right:

All the basic WISE data are in IPAC in a static format. We can go ahead and get the images down provided we know what the appropriate WISE coadd IDs are. This can be obtained from catalogs like wise_allwise_p3am_cdd in astroquery.

A quick gist of the code to build the mosaics.

Again, we come to units and the desire to get them to MJy/sr. Here the DN counts are given in the WISE data with zero point magnitudes. We have the zero point for WISE band 4 given as $M_0 = 12.980$ and the offset between Vega and AB magnitudes again gets us to:

$$\begin{eqnarray} -2.5\log_{10} \left(\frac{F_{22}}{\mathrm{Jy/pix}}\right) + 8.90 & = & -2.5\log_{10} (I) +12.980 + 6.604 \\ \log_{10} \left(\frac{F_{22}}{\mathrm{Jy/pix}}\right) & = & \log_{10} (I) -0.4(12.980+6.604-8.90) \\ \frac{F_{22}}{\mathrm{Jy/pix}} & = & 5.326\times 10^{-5} I \\ \frac{F_{22}}{\mathrm{MJy/sr}}& = & 5.326\times 10^{-11} \frac{I}{\Omega_{\mathrm{pix}}} \end{eqnarray}$$