Issue |
A&A
Volume 432, Number 1, March II 2005
|
|
---|---|---|
Page(s) | 45 - 67 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20040321 | |
Published online | 22 February 2005 |
The Parkes H I Survey of the Magellanic System*
1
Radioastronomisches Institut, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany e-mail: cbruens@astro.uni-bonn.de
2
Australia Telescope National Facility, CSIRO, PO Box 76, Epping NSW 1710, Australia
3
Department of Astronomy, University of Michigan, Ann Arbor, MI 48109, USA
4
Arecibo Observatory, HC3 Box 53995, Arecibo, PR 00612, USA
5
University of Western Sydney, Locked Bag 1797, Penrith South, DC, NSW 1797, Australia
Received:
24
February
2004
Accepted:
27
October
2004
We present the first fully and uniformly sampled, spatially complete survey of the entire Magellanic System with high velocity resolution
(
km s-1), performed with the Parkes Telescope.
Approximately 24 percent of the southern sky was covered by this survey on a
≈5´ grid with an angular resolution of
. A
fully automated data-reduction scheme was developed for this survey to handle
the large number of
spectra (
). The individual
Hanning smoothed and polarization averaged spectra have an rms brightness
temperature noise of σ = 0.12 K. The final data-cubes have an rms noise
of
K and an effective angular resolution of
≈16´. In this paper we describe the survey parameters, the
data-reduction and the general distribution of the
gas.
The Large Magellanic Cloud (LMC) and the Small Magellanic Cloud
(SMC) are associated with huge gaseous features – the
Magellanic Bridge, the Interface Region, the
Magellanic Stream, and the Leading Arm – with a total
mass of M(
) =
,
if all
gas is at the same distance of 55 kpc.
Approximately two thirds of this
gas is located close to the
Magellanic Clouds (Magellanic Bridge and Interface Region),
and 25% of the
gas is associated with the Magellanic Stream.
The Leading Arm has a four times lower
mass than the
Magellanic Stream, corresponding to 6% of the total
mass
of the gaseous features.
We have analyzed the velocity field of the Magellanic Clouds and their
neighborhood introducing a LMC-standard-of-rest frame. The
in the
Magellanic Bridge shows low velocities relative to the Magellanic
Clouds suggesting an almost parallel motion, while the gas in the
Interface Region has significantly higher relative velocities
indicating that this gas is leaving the Magellanic Bridge building up
a new section of the Magellanic Stream. The Leading Arm is
connected to the Magellanic Bridge close to an extended arm of the
LMC.
The clouds in the Magellanic Stream and the Leading Arm show
significant differences, both in the column density distribution and in the
shapes of the line profiles. The
gas in the Magellanic Stream
is more smoothly distributed than the gas in the Leading Arm.
These morphological differences can be explained if the Leading Arm is
at considerably lower z-heights and embedded in a higher pressure ambient
medium.
Key words: Magellanic Clouds / galaxies: interactions / ISM: structure / ISM: kinematics and dynamics / surveys
© ESO, 2005
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