We will construct extensive maps of the ultraviolet (UV) component of the dust absorption in the milky way halo, using the dense sampling of extragalactic quasars, and the unprecedented ultraviolet…

This federal contract award, valued at $75,231.64, was granted by the National Aeronautics and Space Administration (NASA) to Saint Vincent College, a private university and non-profit organization located in Latrobe, Pennsylvania. The contract is for a research project to construct extensive maps of the ultraviolet (UV) component of dust absorption in the Milky Way halo, using data from the Galaxy Evolution Explorer (GALEX) satellite mission and observations of extragalactic quasars. The project aims to study the distribution of the "2175 Angstrom bump", a broad dust absorption feature in the UV spectrum, and provide tests of existing extinction models. The results will be used to improve UV reddening corrections for objects observed by UV telescopes like the Hubble Space Telescope (HST), GALEX, and the Swift Ultraviolet/Optical Telescope (UVOT). This contract does not have a set-aside designation.

We will construct extensive maps of the ultraviolet (UV) component of the dust absorption in the milky way halo, using the dense sampling of extragalactic quasars, and the unprecedented ultraviolet sky coverage of the galex satellite mission. Quasars are sources of strong ultraviolet flux, and tens of thousands of verified quasars have been reliably detected in both galex UV bands. While there is fairly large intrinsic scatter in the colors of quasars, the mean colors at a given redshift are very stable, and serve as a reference for the quasar population at any location in the sky. Also, the unreddened ultraviolet quasar spectrum can be reliably estimated from the optical spectrum for individual quasars, providing an even more accurate reference for measuring UV extinction. The angular variation of the principal characteristics of the extinction curve from optical to UV wavelengths will be mapped across at least 15,000 square degrees of high galactic latitude sky. A particular focus of this program is the so-called "2175 a bump" -- a broad dust absorption feature in the ultraviolet part of the spectrum. While IT is a ubiquitous feature in our galaxy, the 2175 a bump is apparently less common in other galaxies and quasars. The distribution of the bump strength and its relationship to other known structures in the milky way will provide tests of the origin of this UV feature and its role in the evolution of the galaxy. This program will also provide independent tests of the widely used extinction models derived from other studies, and extend the extinction models to ultraviolet wavelengths. The results will be used to apply better ultraviolet reddening corrections to objects detected by UV telescopes, including HST, galex, and the swift uvot.