Three‐dimensional Structure of the Milky Way Disk: The Distribution of Stars and Dust beyond 0.35<i>R</i>_⊙

Abstract

We present a three dimensional model for the Milky Way fit to the\nfar-infrared (FIR) and near-infrared (NIR) data from the COBE/DIRBE instrument\nfor Galactic latitudes |b| &lt; 30 degrees and to within 20 degrees of the\nGalactic center. Because of the low optical depth at 240 microns, the FIR\nemission traces the distribution of galactic dust in the Galaxy. We model the\ndust distribution as due to three components: a warped exponential disk with\nscale length 0.28 R_sun and a flaring scale height, a spiral arm component with\nfour arms as traced by Galactic HII regions, and the local (Orion) arm which\nproduces prominent emission features at galactic longitude l approx. 80 and\n-100 degrees. A Cosmic Infrared Background of 1.07 MJy/sr is recovered,\nconsistent with previous determinations. The dust distribution is then used to\ncalculate absorption in J and K, and the stellar emission in these wavebands is\nmodeled with two components: a warped exponential disk with a scale length of\n0.28 R_sun and a spiral arm component dominated by two arms. This small scale\nlength is consistent with a maximal disk model for our Galaxy, which is\ninconsistent with the cuspy dark matter halos predicted in CDM models. We find\ndifferent amplitudes for the warp in the stars and dust, which starts within\nthe Solar Circle.\n