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The dust extinction curve is a critical component of many observational programs and an important diagnostic of the physics of the interstellar medium. Here we present new measurements of the dust extinction curve and its variation towards tens of thousands of stars, a hundred-fold larger sample than in existing detailed studies. We use data from the APOGEE spectroscopic survey in combination with ten-band photometry from Pan-STARRS1, 2MASS, and WISE. We find that the extinction curve in the optical through infrared is well characterized by a one-parameter family of curves described by R(V). The extinction curve is more uniform than suggested in past works, with sigma(R(V)) = 0.18, and with less than one percent of sight lines having R(V) > 4. Our data and analysis have revealed two new aspects of Galactic extinction: first, we find significant, wide-area variations in R(V) throughout the Galactic plane. These variations are on scales much larger than individual molecular clouds, indicating that R(V) variations must trace much more than just grain growth in dense molecular environments. Indeed, we find no correlation between R(V) and dust column density up to E(B-V) ~ 2. Second, we discover a strong relationship between R(V) and the far-infrared dust emissivity.
Based on the data obtained from the Spitzer/GLIPMSE Legacy Program and the 2MASS project, we derive the extinction in the four IRAC bands, [3.6], [4.5], [5.8] and [8.0] micron, relative to the 2MASS Ks band (at 2.16 micron) for 131 GLIPMSE fields alo
A precise extinction law is a critical input when interpreting observations of highly reddened sources such as young star clusters and the Galactic Center (GC). We use Hubble Space Telescope observations of a region of moderate extinction and a regio
In the fundamental quest of the rotation curve of the Milky Way, the tangent-point (TP) method has long been the simplest way to infer velocities for the inner, low latitude regions of the Galactic disk from observations of the gas component. We test
We measured the mid-infrared (MIR) extinction using Spitzer photometry and spectroscopy (3.6--37 micron) for a sample of Milky Way sightlines (mostly) having measured ultraviolet extinction curves. We used the pair method to determine the MIR extinct
We investigate interstellar extinction curve variations toward $sim$4 deg$^{2}$ of the inner Milky Way in $VIJK_{s}$ photometry from the OGLE-III and $VVV$ surveys, with supporting evidence from diffuse interstellar bands and $F435W,F625W$ photometry