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THE SPECTRUM OF THE DIFFUSE GALACTIC LIGHT: THE MILKY WAY IN SCATTERED LIGHT

Author(s): Brandt, Timothy D; Draine, Bruce T.

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 Abstract: We measure the optical spectrum of the diffuse Galactic light (DGL)-the local Milky Way in reflection-using 92,000 blank sky spectra from the Sloan Digital Sky Survey (SDSS). We correlate the SDSS optical intensity in regions of blank sky against 100 mu m intensity independently measured by the Cosmic Background Explorer and Infrared Astronomy satellites, which provides a measure of the dust column density times the intensity of illuminating starlight. The spectrum of scattered light is very blue and shows a clear 4000 angstrom break and broad Mg b absorption. This is consistent with scattered starlight, and the continuum of the DGL is well reproduced by a simple radiative transfer model of the Galaxy. We also detect line emission in H alpha, H beta, [N II], and [S II], consistent with scattered light from the local interstellar medium. The strength of [N II] and [S II], combined with upper limits on [O III] and He I, indicates a relatively soft ionizing spectrum. We find that our measurements of the DGL can constrain dust models, favoring a grain size distribution with relatively few large grains. We also estimate the fraction of high-latitude H alpha which is scattered to be 19% +/- 4%. Publication Date: 10-Jan-2012 Electronic Publication Date: 22-Dec-2011 Citation: Brandt, Timothy D, Draine, BT. (2012). THE SPECTRUM OF THE DIFFUSE GALACTIC LIGHT: THE MILKY WAY IN SCATTERED LIGHT. ASTROPHYSICAL JOURNAL, 744 (10.1088/0004-637X/744/2/129 DOI: doi:10.1088/0004-637X/744/2/129 ISSN: 0004-637X Type of Material: Journal Article Journal/Proceeding Title: ASTROPHYSICAL JOURNAL Version: Final published version. Article is made available in OAR by the publisher's permission or policy. Notes: Supplementary data may be available at http://simbad.u-strasbg.fr/simbad/sim-ref?querymethod=bib&simbo=on&submit=submit+bibcode&bibcode=2012ApJ...744..129B

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