THE VELA CLOUD: A GIANT H I ANOMALY IN THE NGC 3256 GROUP

Journal Article · Fri Jan 15 04:00:00 EST 2010 · Astronomical Journal (New York, N.Y. Online)

DOI:https://doi.org/10.1088/0004-6256/139/1/102; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21301459

English, Jayanne ^[1]; Koribalski, B ^[2]; Bland-Hawthorn, J ^[3]; Freeman, K C; McCain, Claudia F ^[4]

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1. Department of Physics and Astronomy, University of Manitoba, Winnipeg, MB, R3T 2N2 (Canada)
2. Australia Telescope National Facility, CSIRO, P.O. Box 76 Epping, NSW 1710 (Australia)
3. Sydney Institute for Astronomy, School of Physics A29, University of Sydney, NSW 2006 (Australia)
4. Research School of Astronomy and Astrophysics, Australian National University, Mount Stromlo Observatory, Cotter Road, Weston Creek, ACT 2611 (Australia)

We present Australia Telescope Compact Array (ATCA) observations of a galaxy-sized intergalactic H I cloud ('the Vela Cloud') in the NGC 3256 galaxy group. The group contains the prominent merging galaxy NGC 3256, which is surrounded by a number of H I fragments, the tidally disturbed galaxy NGC 3263, and several other peculiar galaxies. The Vela Cloud, with an H I mass of 3-5 x 10{sup 9} M{sub odot}, resides southeast of NGC 3256 and west of NGC 3263, within an area of 9' x 16' (100 kpc x 175 kpc for an adopted distance of 38 Mpc). In our ATCA data the Vela Cloud appears as three diffuse components and contains four density enhancements. The Vela Cloud's properties, together with its group environment, suggest that it has a tidal origin. Each density enhancement contains {approx}10{sup 8} M{sub odot} of H I gas, which is sufficient material for the formation of globular cluster progenitors. However, if we represent the enhancements as Bonnor-Ebert spheres, then the pressure of the surrounding H I would need to increase by at least a factor of 9 in order to cause the collapse of an enhancement. Thus we do not expect them to form massive bound stellar systems like super star clusters or tidal dwarf galaxies. Since the H I density enhancements have some properties in common with high-velocity clouds, we explore whether they may evolve to be identified with these starless clouds instead.

• OSTI ID: 21301459
• Journal Information: Astronomical Journal (New York, N.Y. Online), Journal Name: Astronomical Journal (New York, N.Y. Online) Journal Issue: 1 Vol. 139; ISSN 1538-3881
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
99 GENERAL AND MISCELLANEOUS
CLOUDS
DENSITY
DISTANCE
GALACTIC EVOLUTION
GALAXIES
IMAGES
STAR CLUSTERS
TELESCOPES