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From: Farhad Zadeh  zadeh@oort.astro.nwu.edu 
Reply-To: Farhad Zadeh <zadeh@oort.astro.nwu.edu>
To: hfalcke@mpifr-bonn.mpg.de
Subject: abstract

%astro-ph/0202442
\title{The Origin of X-ray Emission from a Galactic Center Molecular Cloud: 
Low Energy Cosmic Ray Electrons}
\author{F. Yusef-Zadeh, C. Law and M. Wardle}

\begin{abstract}
The Galactic center region near l$\approx0.2^0$ hosts a mixture of nonthermal
linear filaments and thermal radio continuum features associated with the 
radio
Arc. Chandra observations of this region reveal an X-ray filament and diffuse
emission with an extent of roughly 60$''\times2''$ and 5$'\times3'$,
respectively. The X-ray filament lies at the edge of the nonthermal radio
filaments and a dense molecular shell G0.13-0.13 that has an unusually high
kinetic temperature $\ge$70K. These observations demonstrate that the
G0.13--0.13 molecular cloud and the nonthermal radio filaments of the Arc are
interacting. The diffuse X-ray emission is correlated with the molecular shell
and is fitted either by two-temperature (1 and 10 keV) thermal emission or by
power-law and 1 keV thermal gas. Fluorescent 6.4 keV line emission is also
detected throughout the molecular shell. This cloud coincides within the error
circle of a steady unidentified EGRET source 3EGJ1746--2851. We argue that
low-energy cosmic ray electrons (LECRe) produce the power-law continuum by
bremsstrahlung and 6.4 keV line emission from the filament and the diffuse
cloud with the implication on the origin of the Galactic ridge X-ray emission.
The strong 6.4 keV Fe-line emission seen from other Galactic center clouds
could be produced in a similar fashion rather than via fluorescent emission
induced by a transient hard X-ray source in the Galactic center. In addition,
heating by ionization induced by LECRe are also responsible for the high
temperature of G0.13-0.13. The gamma-ray source is a result of brehmsstrahlung
by the high-energy tail of the electron energy distribution.
\end{abstract}





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  ___      ___   _____   ___   _____  |PD Dr. Heino Falcke
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