J/A+A/426/81 Kinematic analysis of the Minispiral (Paumard+, 2004)
Kinematic and structural analysis of the Minispiral in the Galactic Center from
BEAR spectro-imagery.
Paumard T., Maillard J.-P., Morris M.
<Astron. Astrophys. 426, 81 (2004)>
=2004A&A...426...81P 2004A&A...426...81P
ADC_Keywords: H II regions ; Infrared sources ; Space velocities
Keywords: Galaxy: center - ISM: individual objects: Sgr A West -
ISM: kinematics and dynamics - infrared: ISM -
instrumentation: interferometers - line: profiles
Description:
We have obtained BEAR spectro-imaging data of the Galactic Center HII
region "Sgr A West", also known as the "Minispiral", in the hydrogen
Brackett γ line (2.166 microns). Through multi-component line
fitting, we have decomposed this HII region into nine overlapping
velocity structures, for which we have extracted the line flux and
radial velocity maps.
We have then fitted a set of Keplerian orbits onto the radial velocity
map of the most extended structure (the "Northern Arm"), assuming that
it was orbiting the central black hole candidate Sgr A*. This fit
allows us to propose a three-dimensional kinematic model for this
structure, which is hereby given as a set of FITS files.
In this model, the central mass, its location in the field, and the
distance to the Galactic Center are fixed: we use a mass of 3e6 solar
masses and a distance of 8kpc; the pixel scale is 0.353 arcsec/pix,
Sgr A* is considered to be located at pixel (59.2538, 38.9849) (IDL
notation: (0, 0) is the center of the lower-left pixel, add 1 for FITS
convention).
Objects:
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RA (2000) DE Designation(s)
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17 45 39.95 -29 00 28.2 Sgr A West
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Note: The position given here is that of the radio source and supermassive
black hole candidate Sgr A*, at the focus of the orbits in our model.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig7a.fit 2880 82 *Three-dimensional velocity map in km/s
fig7aerr.fit 2880 82 *Error bars for fig7a.fit in km/s
fig7b.fit 2880 28 *Line-of-sight distance in mas
fig7berr.fit 2880 28 *Error bars for fig7b.fit in mas
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Note on fig7a.fit:
Three-dimensional velocity map, a stack of three images (on the third
axis of the FITS file) giving, in km/s, the velocity in each of the
three dimensions: eastwards (V_alpha), northwards (V_delta), and
outwards (V_radial).
Note on fig7b.fit:
Line-of-sight distance relative to the plane containing the central
mass (Sgr A*), in equivalent milli-arcseconds on the sky. Positive for
points of the structure further away from the observer than the
central mass.
Note on fig7aerr.fit and fig7berr.fit:
The error bars are evaluated as follows: each fitting parameter is
slightly moved within the range where moving it does not change Chi2
by more than 2 sigma. For each point of the field, we keep the highest
and lowest values for each of the 4 variables we are interested in
(LOS distance plus 3D velocity). The error bar is then (highest
value-lowest value)/2.
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Acknowledgements: Thibaut Paumard, paumard(at)mpe.mpg.de
References:
Maillard, J. P., 1995, 3D-Spectroscopy with a Fourier Transform Spectrometer,
in Tridimensional Optical Spectroscopic Methods in Astrophysics, ed.
G. Comte & M. Marcelin, ASP Conf. Ser., 71, 316, 1995tosm.conf..316M
Maillard, J. P. 2000, BEAR Imaging FTS: High Resolution Spectroscopy in
Infrared Emission Lines, in Imaging the Universe in Three Dimensions, ed.
W. van Breugel & J. Bland-Hawthorn, ASP Conf. Ser., 195, 185,
2000iutd.conf..185M
(End) Paumard [Max-Planck-Institut fuer extraterrestrische Physik] 09-Jul-2004