148 research outputs found
Preliminary Evaluation of the Kepler Input Catalog Extinction Model Using Stellar Temperatures
The Kepler Input Catalog (KIC) provides reddening estimates for its stars,
based on the assumption of a simple exponential dusty screen. This project
focuses on evaluating and improving these reddening estimates for the KIC's
giant stars, for which extinction is a much more significant concern than for
the nearby dwarf stars. We aim to improve the calibration (and thus
consistency) amongst various photometric and spectroscopic temperatures of
stars in the Kepler field by removing systematics due to incorrect extinction
assumptions. The revised extinction estimates may then be used to derive
improved stellar and planetary properties. We plan to eventually use the large
number of KIC stars as probes into the structure and properties of the Galactic
ISM.Comment: Proc. of the workshop "Asteroseismology of stellar populations in the
Milky Way" (Sesto, 22-26 July 2013), Astrophysics and Space Science
Proceedings, (eds. A. Miglio, L. Girardi, P. Eggenberger, J. Montalban
Lifting the Dusty Veil With Near- and Mid-Infrared Photometry: III. Two-Dimensional Extinction Maps of the Galactic Midplane Using the Rayleigh-Jeans Color Excess Method
We provide new, high-resolution A(Ks) extinction maps of the heavily reddened
Galactic midplane based on the Rayleigh-Jeans Color Excess ("RJCE") method.
RJCE determines star-by-star reddening based on a combination of near- and
mid-infrared photometry. The new RJCE-generated maps have 2 x 2 arcmin pixels
and span some of the most severely extinguished regions of the Galaxy -- those
covered with Spitzer+IRAC imaging by the GLIMPSE-I, -II, -3D, and Vela-Carina
surveys, from 256<l<65 deg and, in general, for |b| <= 1-1.5 deg (extending up
to |b|<=4 deg in the bulge). Using RJCE extinction measurements, we generate
dereddened color-magnitude diagrams and, in turn, create maps based on main
sequence, red clump, and red giant star tracers, each probing different
distances and thereby providing coarse three-dimensional information on the
relative placement of dust cloud structures. The maps generated from red giant
stars, which reach to ~18-20 kpc, probe beyond most of the Milky Way extinction
in most directions and provide close to a "total Galactic extinction" map -- at
minimum they provide high angular resolution maps of lower limits on A(Ks).
Because these maps are generated directly from measurements of reddening by the
very dust being mapped, rather than inferred on the basis of some less direct
means, they are likely the most accurate to date for charting in detail the
highly patchy differential extinction in the Galactic midplane. We provide
downloadable FITS files and an IDL tool for retrieving extinction values for
any line of sight within our mapped regions.Comment: 23 pages, 5 figures, accepted for publication in ApJ
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Mapping The Interstellar Medium With Near-Infrared Diffuse Interstellar Bands
We map the distribution and properties of the Milky Way's interstellar medium as traced by diffuse interstellar bands (DIBs) detected in near-infrared stellar spectra from the SDSS-III/APOGEE survey. Focusing exclusively on the strongest DIB in the H band, at lambda similar to 1.527 mu m, we present a projected map of the DIB absorption field in the Galactic plane, using a set of about 60,000 sightlines that reach up to 15 kpc from the Sun and probe up to 30 mag of visual extinction. The strength of this DIB is linearly correlated with dust reddening over three orders of magnitude in both DIB equivalent width (Wpm) and extinction, with a power law index of 1.01 +/- 0.01, a mean relationship of W-DIB/A(v) = 0.1 angstrom mag(-1) and a dispersion of similar to 0.05 angstrom mag(-1) at extinctions characteristic of the Galactic midplane. These properties establish this DIB as a powerful, independent probe of dust extinction over a wide range of Av values. The subset of about 14,000 robustly detected DIB features have a W-DIB distribution that follows an exponential trend. We empirically determine the intrinsic rest wavelength of this transition to be lambda(0) = 15 272.42 angstrom and use it to calculate absolute radial velocities of the carrier, which display the kinematical signature of the rotating Galactic disk. We probe the DIB carrier distribution in three dimensions and show that it can be characterized by an exponential disk model with a scale height of about 100 pc and a scale length of about 5 kpc. Finally, we show that the DIB distribution also traces large-scale Galactic structures, including the Galactic long bar and the warp of the outer disk.NSF Astronomy & Astrophysics Postdoctoral Fellowship AST-1203017NSF AST-1109665Alfred P. Sloan FoundationNational Science FoundationU.S. Department of Energy Office of ScienceUniversity of ArizonaBrazilian Participation GroupBrookhaven National LaboratoryUniversity of CambridgeCarnegie Mellon UniversityUniversity of FloridaFrench Participation GroupGerman Participation GroupHarvard UniversityInstituto de Astrofisica de CanariasMichigan State/Notre Dame/JINA Participation GroupJohns Hopkins UniversityLawrence Berkeley National LaboratoryMax Planck Institute for AstrophysicsMax Planck Institute for Extraterrestrial PhysicsNew Mexico State UniversityNew York UniversityOhio State UniversityPennsylvania State UniversityUniversity of PortsmouthPrinceton UniversitySpanish Participation GroupUniversity of TokyoUniversity of UtahVanderbilt UniversityUniversity of VirginiaUniversity of WashingtonYale UniversitySpanish Ministry of Economy and Competitiveness AYA-2011-27754McDonald Observator
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