2d adaptive extinction maps for the VVV footprint

<p><strong>2d adaptive resolution extinction maps for the VVV footprint</strong></p> <p>Extinction maps associated with the publication&nbsp;<a href="https://ui.adsabs.harvard.edu/abs/2022arXiv220510378S">Sanders et al. (2022, MNRAS)</a>&nbsp;</p> <p>Three maps are provided: E(J-Ks), E(H-Ks) and E(H-[4.5]). The E(J-Ks) and E(H-Ks) maps have been computed over the entire VVV footprint whilst the E(H-[4.5]) map is only computed for the inner -1.5&lt;l&lt;1.5, -1.5&lt;b&lt;1.5. To convert to AKs multiply by 0.449, 1.293, 0.700 respectively (or otherwise for other extinction laws).</p> <p>The files *.csv.gz give the colour excess (e*) and its spread (sigma_e*) at a set of Healpix labelled by their unique index. A series of Healpix resolutions have been used to provide higher resolution where needed (except for the E(H-[4.5]) map that is only at level=13). The indices are using the nested scheme given the Galactic coordinates (l,b). In this way, it is simple to handle the varying resolution (see&nbsp;<a href="https://ivoa.net/documents/MOC/">https://ivoa.net/documents/MOC/</a>).</p> <p>The colour excesses have been found from Gaussian fits to the red clump colours for (J-Ks) and (H-Ks) and an average over all giant stars for (H-[4.5]) (accounting for the weak gradient of the giant branch in the (H-[4.5]) vs. Ks colour-magnitude space). The spreads in extinction come from the width of the Gaussian peak for&nbsp;(J-Ks) and (H-Ks)&nbsp;and the width of the full distribution for (H-[4.5]) after subtracting the average photometric uncertainties and accounting for a (0.05,0.02,0.00) intrinsic colour width for (J-Ks, H-Ks, H-[4.5]) respectively.</p> <p>The provided file extinction_maps.py provides a class for reading in all extinction maps (version=JK,HK,H45 allows one to pick the required map) and querying the colour excess and its spread&nbsp;for large numbers of Galactic coordinates. Also there is functionality for finding the resolution of the map at a given location.</p> <p>The queries will throw a warning but return a value if the coordinate is outside the reliable footprint (the entire VVV footprint for JK and HK and the inner -1.5&lt;l&lt;1.5, -1.5&lt;b&lt;1.5 for H45).</p> <p>The example.ipynb notebook shows an example of querying the extinction map and plotting the result.</p> <p>&nbsp;</p> <p>&nbsp;</p>