Galactic cirri in deep optical imaging

The ubiquitous presence of Galactic cirri in deep optical images represents a major obstacle to study the low surface brightness features of extragalactic sources. To address this issue, we have explored the optical properties of cirri using g, r, i and z bands in the Sloan Digital Sky Survey (SDSS) Stripe82 region. Using state-of-the-art $-$custom made$-$ image processing techniques, including the modeling and removal of the scattered light produced by the stars, we manage to isolate the optical diffuse emission by the cirri, allowing their photometric characterization. We find that their optical colors are driven by the dust column density: the cirri become redder as their 100 $\mu$m emission increases. This could explain the extended red emission previously found in dust clouds. In most cases, the optical colors of the Galactic cirri differ significantly from those of extragalactic sources. If future works confirm our findings, it would be possible the use of deep multi-band optical photometry (as the one produced by LSST) to identify the presence of cirri at a higher spatial resolution than those provided by far infrared observations. The combination of very deep data and multi-band photometry would make possible to build dust and extinction maps of unprecedented quality.