------------------------------------------------------------------------
 0209.tex A&A, 2004, in press
From: Thibaut Paumard <paumard@mpe.mpg.de>
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%astro-ph/0405197
\documentclass{aa}

\usepackage{natbib}
\usepackage{graphicx} 
\usepackage{txfonts}
\usepackage{placeins}
\usepackage{ifthen}
\usepackage{sidecap}

\title{Kinematic  and structural  analysis of  the Minispiral  in the
Galactic  Center from BEAR  spectro-imagery}

\titlerunning{Kinematic and structural analysis of the Minispiral}

\author{%
  Thibaut Paumard%
    \inst{1}\fnmsep%
%
    \thanks{Visiting          Astronomer,
    Canada-France-Hawaii Telescope, operated  by the National Research
Council
    of Canada, le  Centre National de la Recherche  Scientifique de
France and
    the     University      of     Hawaii.}\fnmsep%
%  
   \thanks{Present   address:   Max-Planck-Institut  f\"ur  
extraterrestrische
    Physik,  Postfach  1312,   D-85741  Garching,  Germany.}
%%
  \and  Jean-Pierre Maillard\inst{1}\fnmsep$^{\star\star}$
%%
  \and Mark Morris\inst{2}%
}

\institute{%
 Institut d'astrophysique de Paris (CNRS),  98b Blvd Arago, 75014 Paris,
France
  \and
 University of California, Los Angeles, Div.  of Astronomy, Dept of
Physics and
  Astronomy, Los Angeles, CA 90095-1562, USA%
}

\offprints{T.~Paumard, \email{paumard@mpe.mpg.de}}

\date{Received 19 August 2003 / Accepted 4 May 2004}

\abstract{Integral  field spectroscopy  of the  inner region  of  the Galactic
  Center, over  a field of roughly $40\arcsec\times40\arcsec$  was obtained at
  2.06~$\mu$m  (\ion{He}{i})  and  2.16~$\mu$m  (Br$\gamma$)  using  BEAR,  an
  imaging Fourier Transform Spectrometer, at spectral resolutions respectively
  of  52.9~km~s$^{-1}$  and  21.3~km~s$^{-1}$,  and a  spatial  resolution  of
  $\simeq~0.5\arcsec$.  The analysis of the data was focused on the kinematics
  of  the   gas  flows,  traditionally   called  the  ``\object{Minispiral}'',
  concentrated   in   the   neighborhood    of   the   central   black   hole,
  \object{Sgr~A$^{\star}$}.   From  the  decomposition into  several  velocity
  components (up to  four) of the line profile extracted at  each point of the
  field, velocity  features were identified.   Nine distinguishable structures
  are  described: the  standard \object{Northern  Arm},  \object{Eastern Arm},
  \object{Bar}, \object{Western  Arc}, and five  additional, coherently-moving
  patches of gas.   From this analysis, the \object{Northern  Arm} appears not
  limited, as usually thought, to  the bright, narrow North-South lane seen on
  intensity  images,   but  it  consists   instead  of  a   weak,  continuous,
  triangular-shaped surface, drawn out into a narrow stream in the vicinity of
  \object{Sgr~A$^{\star}$} where  it shows a  strong velocity gradient,  and a
  bright western rim.  The \object{Eastern Arm} is split into three components
  (a \emph{Ribbon} and  a \emph{Tip}, separated by a  cavity, and an elongated
  feature parallel to the Ribbon:  the \emph{Eastern Bridge}).  We also report
  extinction of  some interstellar  structures by other  components, providing
  information on their relative position along the line of sight.  A system of
  Keplerian orbits can be fitted to most of the \object{Northern Arm}, and the
  bright  rim of this  feature can  be interpreted  in terms  of line-of-sight
  orbit crowding caused  by the warping of the flowing  surface at the western
  edge facing  \object{Sgr~A$^{\star}$}.  These results lead to  a new picture
  of the gas structures in \object{Sgr~A West}, in which large-scale gas flows
  and isolated gas  patches coexist in the gravitational  field of the central
  Black Hole.  The question of the  origin of the ionized gas is addressed and
  a   discussion  of   the  lifetime   of   these  features   is  presented.   
  \keywords{infrared -- spectro-imaging -- FTS -- Galaxy: Center -- Sgr~A West
    -- ionized gas}}


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