------------------------------------------------------------------------ gc_march09.tex Apj, accepted Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-MailScanner-Information: Please contact the postmaster@aoc.nrao.edu for more information X-MailScanner: Found to be clean X-MailScanner-SpamCheck: not spam, SpamAssassin (not cached, score=-4, required 5, autolearn=disabled, RCVD_IN_DNSWL_MED -4.00) X-MailScanner-From: mmontero@cfa.harvard.edu X-Spam-Status: No %astro-ph/0903.0886 \documentclass{emulateapj} \newcommand{\vdag}{(v)^\dagger} \newcommand{\myemail}{mmontero@cfa.harvard.edu} \slugcomment{Accepted by ApJ} \shorttitle{Gas infall towards Sgr~A*} \shortauthors{Montero-Casta{\~n}o, Herrnstein and Ho} \begin{document} \title{Gas infall towards Sgr~A* from the clumpy circumnuclear disk} \author{Mar{\'{\i}}a Montero-Casta{\~n}o\altaffilmark{1,2,3}, Robeson M. Herrnstein\altaffilmark{4} and Paul T.P. Ho\altaffilmark{1,3}} \altaffiltext{1}{Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138; mmontero@cfa.harvard.edu, pho@cfa.harvard.edu.} \altaffiltext{2}{Departamento de Astrof{\'{\i}}sica, Facultad de Ciencias F{\'{\i}}sicas, Universidad Complutense de Madrid, 28040-Madrid, Spain.} \altaffiltext{3}{Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23141, Taipei 106, Taiwan.} \altaffiltext{4}{Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027; herrnstein@astro.columbia.edu} \altaffiltext{5}{The Submillimeter Array is a joint project between the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics, and is funded by the Smithsonian Institution and the Academia Sinica.} \begin{abstract} We present the first large-scale mosaic performed with the Submillimeter Array (SMA$^{5}$) in the Galactic center. We have produced a 25-pointing mosaic, covering a $\sim$~2$\arcmin$~$\times$~2$\arcmin$ area around Sgr~A*. We have detected emission from two high-density molecular tracers, HCN(4-3) and CS(7-6), the latter never before reported in this region. The data have an angular resolution of 4.6$\arcsec$~$\times$~3.1$\arcsec$, and the spectral window coverage is from -180~km~s$^{-1}$ to 1490~km~s$^{-1}$ for HCN(4-3) and from -1605~km~s$^{-1}$ to 129~km~s$^{-1}$ for CS(7-6). Both molecular tracers present a very clumpy distribution along the circumnuclear disk (CND), and are detected with a high signal-to-noise ratio in the southern part of the CND, while they are weaker towards the northern part. Assuming that the clumps are as close to the Galactic center as their projected distances, they are still dense enough to be gravitationally stable against the tidal shear produced by the supermassive black hole. Therefore, the CND is a non-transient structure. This geometrical distribution of both tracers suggests that the southern part of the CND is denser than the northern part. Also, by comparing the HCN(4-3) results with HCN(1-0) results we can see that the northern and the southern parts of the CND have different excitation levels, with the southern part warmer than the northern. Finally, we compare our results with those obtained with the detection of NH$_3$, which traces the warmer and less dense material detected in the inner cavity of the CND. We suggest that we are detecting the origin point where a portion of the CND becomes destabilized and approaches the dynamical center of the Milky Way, possibly being impacted by the {\it southern streamer} and heated on its way inwards. \end{abstract} \end{document}