H I extent and deficiency of spiral galaxies in the Virgo cluster
Neutral hydrogen observations mapping along the optical major axis have been made with the Arecibo 305-m telescope and flat feed system for 24 spiral galaxies in the Virgo cluster. Comparison of observed flux integrals with those obtained from a numerical convolution of the antenna beam pattern and an assumed H I surface density distribution yields a measure of an effective H I size, taken to be that radius interior to which lies 70% of the total H I mass. The neutral hydrogen properties of the Virgo cluster spirals have been compared with those of a similar sample of isolated galaxies. We find that, for a given optical diameter, a Virgo core galaxy has a smaller H I extent than its optical counterpart; we measure the ratio of the H I to optical Holmberg diameter d/sub Htsi//d/sub Ho/ to be 0.70 for the 19 galaxies within a five degree projected radius of the cluster center, whereas those outside show d/sub Htsi//d/sub Ho/ approx. =1.10. Using the relation derived between the optical linear diameter and the H I mass, we are able to define a H I deficiency parameter and find that the galaxies in the Virgo core are, on the average, H I deficient by a factor of 2.7 with respect to the isolated galaxies. The similarity of the relationship between the H I mass and the H I linear diameter, within the statistical errors, for both gas deficient and normal galaxies, implies that the linear extent of the H I distribution within a galaxy is well correlated with its total H I mass. The stripping mechanisms responsible for the H I deficiency observed in cluster galaxies, therefore, do not substantially alter the average H I surface density, but rather lower the H I mass and size to values expected for an optically smaller galaxy. The dependence of the H I deficiency on the velocity of a galaxy with respect to the cluster suggests that the mechanism responsible for the removal of the interstellar gas from the galaxy is the ram pressure sweeping of the intracluster gas.
- Research Organization:
- Arecibo Observatory, Arecibo, Puerto Rico 00613
- OSTI ID:
- 5984198
- Journal Information:
- Astron. J.; (United States), Vol. 88:7
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
GALAXIES
H1 REGIONS
GALAXY CLUSTERS
SPATIAL DISTRIBUTION
GHZ RANGE 01-100
SPIRAL CONFIGURATION
CONFIGURATION
COSMIC RADIO SOURCES
DISTRIBUTION
FREQUENCY RANGE
GHZ RANGE
640103* - Astrophysics & Cosmology- Quasi-Stellar
Radio
& X-Ray Sources- (-1987)
640105 - Astrophysics & Cosmology- Galaxies