A colour-excess extinction map of the southern Galactic disc from the VVV and GLIMPSE surveys

Abstract

An improved high-resolution and deep A_Ks foreground dust extinction map is presented for the Galactic disc area within 295&deg; ≲ l ≲ 350&deg;, &minus;1.0&deg; ≲ <em>b</em> ≲ +1.0&deg;. At some longitudes the map reaches up to |<em>b</em>| &sim; 2.25&deg;, for a total of &sim;148&thinsp;deg². The map was constructed via the Rayleigh&ndash;Jeans colour excess (RJCE) technique based on deep near-infrared (NIR) and mid-infrared (MIR) photometry. The new extinction map features a maximum bin size of 1', and relies on NIR observations from the Two Micron All-Sky Survey (2MASS) and new data from ESO&rsquo;s Vista Variables in the V&iacute;a L&aacute;ctea (VVV) survey, in concert with MIR observations from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire. The VVV photometry penetrates &sim;4&thinsp;mag fainter than 2MASS, and provides enhanced sampling of the underlying stellar populations in this heavily obscured region. Consequently, the new results supersede existing RJCE maps tied solely to brighter photometry, revealing a systematic underestimation of extinction in prior work that was based on shallower data. The new high-resolution and large-scale extinction map presented here is readily available to the community through a web query interface.