Kinematic and structural analysis of the Minispiral in the Galactic Center from BEAR spectro-imagery

Free access article

Issue		A&A Volume 426, Number 1, October IV 2004


Page(s)		81 - 96
Section		Interstellar and circumstellar matter
DOI		http://dx.doi.org/10.1051/0004-6361:20034209

A&A 426, 81-96 (2004)
DOI: 10.1051/0004-6361:20034209

Kinematic and structural analysis of the Minispiral in the Galactic Center from BEAR spectro-imagery

T. Paumard¹, J.-P. Maillard¹ and M. Morris²

¹ Institut d'astrophysique de Paris (CNRS), 98b Bd. Arago, 75014 Paris, France
e-mail: paumard@mpe.mpg.de
² University of California, Los Angeles, Div. of Astronomy, Dept of Physics and Astronomy, Los Angeles, CA 90095-1562, USA

(Received 19 August 2003 / Accepted 23 April 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 " Minispiral ", concentrated in the neighborhood of the central black hole, 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 Northern Arm , Eastern Arm , Bar , Western Arc , and five additional, coherently-moving patches of gas. From this analysis, the 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 Sgr A $^{\star}$ where it shows a strong velocity gradient, and a bright western rim. The Eastern Arm is split into three components (a Ribbon and a Tip, separated by a cavity, and an elongated feature parallel to the Ribbon: the 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 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 Sgr A $^{\star}$ . These results lead to a new picture of the gas structures in 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.

Key words: Galaxy: center -- ISM: individual objects: Sgr A West -- ISM: kinematics and dynamics -- infrared: ISM -- Instrumentation: interferometers -- line: profiles

SIMBAD Objects
Tables at the CDS

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.