March 7
Abstract:
From inside the Milky Way, we have the unique opportunity to study an L*
spiral galaxy in great detail. Using photometry from SDSS and 2MASS, we
simultaneously fit main-sequence spectral energy distribution (SED) and amount
of dust extinction along the line of sight towards each star. When using both
SDSS and 2MASS photometry, the ratio of the total to selective absorption, RV,
can be determined with an uncertainty of about 0.1 for most stars in
high-extinction regions. These fits enable detailed studies of the dust
properties and its spatial distribution, and of the stellar spatial
distribution at low Galactic latitudes (|b| less than 30 degrees). Our results are in good
agreement with the extinction normalization given by the Schlegel, Finkbeiner,
and Davis (1998, SFD) dust maps at high northern Galactic latitudes. However, we
demonstrate that at low Galactic latitudes, the SFD maps cannot be reliably
used to correct for extinction because most stars are embedded in dust, rather
than behind it. We analyze three-dimensional maps of the best-fit RV and find
that RV=3.1 cannot be ruled out in any of the ten SEGUE stripes at a precision
level of ~0.1-0.2. Finally, we make these best-fit parameters, as well as all
the input SDSS and 2MASS data publicly available.