------------------------------------------------------------------------ paper ApJ, Feb 2007, in press Message-ID: MIME-Version: 1.0 Content-Type: MULTIPART/MIXED; BOUNDARY="1770104983-1282552844-1163487224=:3876" X-MailScanner-Information: Please contact postmaster@aoc.nrao.edu for more information X-MailScanner: Found to be clean X-MailScanner-SpamCheck: not spam, SpamAssassin (score=0, required 5, autolearn=disabled) X-MailScanner-From: zadeh@northwestern.edu X-Spam-Status: No This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --1770104983-1282552844-1163487224=:3876 Content-Type: TEXT/PLAIN; charset=X-UNKNOWN; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE %arXiv:astro-ph/0608710 \documentclass[12pt,preprint]{aastex} \begin{document} \title{The Origin of Diffuse X-ray and $\gamma$-ray Emission from the Galactic Center Region: Cosmic Ray Particles } \author{F. Yusef-Zadeh\altaffilmark{1}, M. Wardle\altaffilmark{3}, Northwestern University, Evanston, Il. 60208 (zadeh@northwestern.edu)} \altaffiltext{2}{Dept Physics and Astronomy, University of California, Los= =20 Angeles, Box 951547, Los Angeles, CA 90095=20 (mmuno@astro.ucla.edu)} \altaffiltext{3}{Department of Physics, Macquarie University, Sydney NSW 21= 09, Australia (wardle@physics.mq.edu.au)} \altaffiltext{4}{California Institute of Technology, MC 320-47, Pasadena, CA 91125=20 (dcl@caltech.edu)} The inner couple hundred pcs of our Galaxy is characterized by significant= =20 amount of synchrotron-emitting gas, which appears to co-exist with a large= =20 reservoir of molecular gas. Many of the best studied sources in this=20 region exhibit a mixture of 6.4 keV Fe K$\alpha$ emission, molecular line= =20 emission and nonthermal radio continuum radiation. The spatial=20 correlation between=A0 fluorescent~Fe K-$\alpha$ line =A0emission at 6.4 ke= V=20 and molecular line emission~ =A0from Galactic center molecular clouds has= =20 been explained as reflected X-rays from a past outburst of Sgr~A*. Here we= =20 present multi-wavelength study of a representative Galactic center cloud=20 Sgr C using {\it Chandra}, {\it VLA} and {\it FCRAO}. We note a=20 correlation between the nonthermal radio filaments in Sgr C and the X-ray= =20 features, suggesting that the two are related. This correlation, when=20 combined with the distribution of molecular gas suggests against the=20 irradiation of Sgr~C by Sgr A*. Instead, we account for this distribution= =20 in terms of the impact of the relativistic particles from local=20 (nonthermal filaments) and extended sources with diffuse neutral gas=20 producing both a nonthermal bremsstrahlung X-ray continuum emission, as=20 well as diffuse 6.4 keV line emission. The production rate of Fe=20 K$\alpha$ photons associated with the injection of electrons into a cloud= =20 as a function of column density is calculated. The required energy=20 density of low-energy cosmic rays associated with the synchrotron emitting= =20 radio filaments or extended features is estimated to be in the range=20 between 20 and $\sim10^3$ eV cm$^{-3}$ for Sgr C, Sgr B1, Sgr B2, and=20 ``the 45 and -30 km s$^{-1}$'' clouds. We also generalize this idea to=20 explain the cosmic-ray heating of molecular gas, the interstellar cosmic=20 ray ionization, the pervasive production of diffuse K${\alpha}$ line and=20 TeV emission from the Galactic center molecular clouds. In particular, we= =20 suggest that Inverse Compton scattering of the sub-millimeter radiation=20 from dust by relativistic electrons may contribute substantially to the=20 large-scale diffuse TeV emission observed towards the central regions of=20 the Galaxy. \end{document} --1770104983-1282552844-1163487224=:3876--