------------------------------------------------------------------------ reid.tex ApJ, 2007, accepted Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII 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: reid@cfa.harvard.edu X-Spam-Status: No % astro-ph/0612164 \documentclass[12pt,preprint]{aastex} %% manuscript produces a one-column, double-spaced document: % \documentclass[manuscript]{aastex} %% preprint2 produces a double-column, single-spaced document: % \documentclass[preprint2]{aastex} \newcommand{\vdag}{(v)^\dagger} \def\etal {et al.} \def\ie {{i.e.},\ } \def\eg {{e.g.},\ } \def\onesig {$1\sigma$} \def\twosig {$2\sigma$} \def\fivesig {$5\sigma$} \def\sixsig {$6\sigma$} \def\mira {$o$~Ceti} \def\sgra {Sgr~A*} \def\msun {M$_\odot$} \def\degrees {$^\circ$} \def\Vorb {\ifmmode {V_{orb}} \else ${V_{orb}}$ \fi} \def\Vdot {\ifmmode {\.V} \else ${\.V}$ \fi} \def\ls{\vskip 12.045pt} \def\hs{\hskip 2.5em} \def\et{{\it et\thinspace al.}\ } \def\arcm{\ifmmode {' }\else $' $\fi} \def\arcs{\ifmmode {'' }\else $'' $\fi} \def\arcmper{\ifmmode \rlap.{'} \else $\rlap{.}' $\fi} \def\arcsper{\ifmmode \rlap.{''} \else $\rlap{.}'' $\fi} \def\porm {\ifmmode\pm\else$\pm$\fi} \def\kms {\ifmmode{{\rm ~km~s}^{-1}}\else{~km~s$^{-1}$}\fi} \def\masy {\ifmmode{{\rm mas~y}^{-1}}\else{mas~y$^{-1}$}\fi} \def\micron {\ifmmode{\mu{\rm m}}\else{$\mu$m}\fi} \def\a {\ifmmode {\rlap.}^{''}\! \else ${\rlap.}^{''}\!$\fi} \def\p {\phantom{0}} \def\q {\phantom{00}} \def\r {\phantom{000}} \def\s {\phantom{0.0000}} \def\blankline {\par\vskip 12 pt} \def\bl {\vskip 0.3truecm} % \newbox\grsign \setbox\grsign=\hbox{$>$} \newdimen\grdimen \grdimen=\ht\grsign \newbox\laxbox \newbox\gaxbox \setbox\gaxbox=\hbox{\raise.5ex\hbox{$>$}\llap {\lower.5ex\hbox{$\sim$}}}\ht1=\grdimen\dp1=0pt \setbox\laxbox=\hbox{\raise.5ex\hbox{$<$}\llap {\lower.5ex\hbox{$\sim$}}}\ht2=\grdimen\dp2=0pt \def\gax{\mathrel{\copy\gaxbox}} \def\lax{\mathrel{\copy\laxbox}} %\slugcomment{2006 December 4} \shorttitle{\sgra\ Position: III} \shortauthors{Reid \etal } \begin{document} \title{The Position of Sagittarius A*: \\ III. Motion of the Stellar Cusp} \author{M. J. Reid} \affil{Harvard--Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138} \email{reid@cfa.harvard.edu} \author{K. M. Menten} \affil{Max-Planck-Institut f\"ur Radioastronomie, Auf dem H\"ugel 69, D-53121 Bonn, Germany} \email{kmenten@mpifr-bonn.mpg.de} \author{S. Trippe, T. Ott \& R. Genzel} \affil{Max-Planck-Institut f\"ur extraterrestrische Physik, Postfach 1312, D-85741 Garching, Germany} \email{trippe@mpe.mpg.de, ott@mpe.mpg.de, genzel@mpe.mpg.de} \begin{abstract} In the first two papers of this series, we determined the position of \sgra\ on infrared images, by aligning the positions of red giant stars with positions measured at radio wavelengths for their circumstellar SiO masers. In this paper, we report detections of 5 new stellar SiO masers within 50'' (2 pc) of \sgra\ and new and/or improved positions and proper motions of 15 stellar SiO masers. The current accuracies are $\approx1$~mas in position and $\approx0.3$~\masy\ in proper motion. We find that the proper motion of the central stellar cluster with respect to \sgra\ is less than $45$~\kms. One star, IRS~9, has a three-dimensional speed of $\approx370$~\kms\ at a projected distance of 0.33~pc from \sgra. If IRS~9 is bound to the inner parsec, this requires an enclosed mass that exceeds current estimates of the sum of the mass of \sgra\ and luminous stars in the stellar cusp by $\approx0.8\times10^6$~\msun. Possible explanations include i) that IRS~9 is not bound to the central parsec and has ``fallen'' from a radius greater than 9~pc, ii) that a cluster of dark stellar remnants accounts for some of the excess mass, and/or iii) that R$_0$ is considerably greater than 8~kpc. \end{abstract} ------------------------------------------------------------- Mark J. Reid Phone: 617-495-7470 Harvard-Smithsonian CfA Fax : 617-495-7345 60 Garden Street Email: reid@cfa.harvard.edu Cambridge, MA 02138, USA Web : cfa-www.harvard.edu/~reid -------------------------------------------------------------