Issue |
A&A
Volume 380, Number 2, December III 2001
|
|
---|---|---|
Page(s) | 673 - 683 | |
Section | The Sun | |
DOI | https://doi.org/10.1051/0004-6361:20011471 | |
Published online | 15 December 2001 |
HI observations of the high-velocity cloud in the direction of M 92 *
1
Astrophysics and Planetary Science Division, Department of Pure and Applied Physics, The Queen's University of Belfast, University Road, Belfast, BT7 1NN, UK
2
National Research Council of Canada, Herzberg Institute of Astrophysics, Dominion Radio Astrophysical Observatory, Penticton, B.C. V2A 6K3, Canada
3
The University of Manchester, Jodrell Bank Observatory, Lower Withington, Macclesfield, Cheshire, SK11 9DL, UK
4
Department of Physics and Astronomy, University of Wales, Cardiff, 5, The Parade, Cardiff, CF24 3YB, UK
Corresponding author: J.smoker, j.smoker@qub.ac.uk
Received:
22
May
2001
Accepted:
16
October
2001
We present wide-field neutral hydrogen (H i) Lovell telescope
multibeam, and Dominion Radio Astrophysical Observatory H i
synthesis observations, of the high velocity cloud (HVC) located in the general
direction of the globular cluster M 92. This cloud is part of the larger
Complex C and lies at velocities between ~-80 and -130 km s-1
in the Local Standard of Rest. The Lovell telescope observations, of resolution
12 arcmin spatially and 3.0 km s-1 in velocity,
fully sampling a 3.112.6° RA-Dec grid,
have found that this part of HVC Complex C comprises two main condensations,
lying approximately north-south in declination, separated by ~2° and
being parallel to the Galactic plane. At this resolution, peak values of the brightness
temperature and H i column density of ~1.4 K and
~5
1019 cm-2 are determined, with relatively high values of the
full width half maximum velocity (FWHM) of ~22 km s-1 being observed, equivalent
to a gas kinetic temperature,
in the absence of turbulence and geometric effects of ~10 000 K. Each of these
properties, as well as the sizes of the clouds, are similar in the two components.
The DRAO observations, towards the Northern HVC condensation, are the first
high-resolution H i spectra of Complex C. When
smoothed to a resolution of 3 arcmin, they identify several H i intensity
peaks with column densities in the range 4-7
1019 cm-2. Further
smoothing of these data to 6 arcmin resolution tentatively indicates that parts of the
HVC consist of two velocity components, of similar brightness temperature,
separated by ~7 km s-1 in velocity, and with FWHM velocity widths
of ~5-7km s-1. No IRAS 60 or 100 micron flux is associated with the M 92 HVC.
Cloud properties are briefly discussed and compared to previous observations
of HVCs.
Key words: ISM: clouds / ISM: individual objects: M 92 HVC / radio lines: ISM
© ESO, 2001
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