Investigation of dwarf galaxies in the Virgo cluster

Journal Article · Wed May 01 00:00:00 EDT 1985 · Astron. J.; (United States)

DOI:https://doi.org/10.1086/113778· OSTI ID:5819870

Bothun, G D; Mould, J R; Wirth, A; Caldwell, N

We have obtained 21-cm H I observations of a sample of 32 dwarf irregular (dI) and 12 dwarf elliptical (dE) galaxies that are located in the Virgo cluster. Altogether, 18 of 32 DIs were detected in H I, but none of the dEs were detected at a sensitivity level of M/sub Htsi/ = 2--3 x 10/sup 6/ M/sub sun/. The detected dIs have M/sub Htsi/>3 x 10/sup 7/ M/sub sun/. This disparity in H I content between dIs and dEs effectively dispels the possibility that the dEs are presently in a stage of quiescence (hibernation), between bursts of star formation. In order to supplement the 21-cm data, we have acquired optical spectroscopy, CCD images, and infrared photometry for a limited subsample of these dwarfs. The most significant result provided by this additional data is that the dEs, although very H I poor, nevertheless have observed (J-K) colors which indicate somewhat high metallicity, implying some degree of enrichment due to multiple generations of star formation. In contrast, most of the dIs are quite H I rich (with some having fractional H I contents that exceed 30% by mass), yet they are apparently in a quiescent phase, judging by their low central surface brightnesses (<10% of sky) and lack of resolution into obvious regions of star formation. A small gas-poor contingent of dIs have been found but there is no apparent correlation between dI gas content and either their velocity with respect to the Virgo ICM or their position in the cluster. In general, the velocity distribution of the dIs is flat with only a weak peak that corresponds to the mean velocity of the brighter galaxies in Virgo.

• Research Organization: Palomar Observatory, California Institute of Technology, Pasadena, California 91101
• OSTI ID: 5819870
• Journal Information: Astron. J.; (United States), Vol. 90:5
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
GALAXIES
CHEMICAL COMPOSITION
H1 REGIONS
MASS
PHOTOMETRY
GALAXY CLUSTERS
BRIGHTNESS
INFRARED RADIATION
RESOLUTION
COSMIC RADIO SOURCES
ELECTROMAGNETIC RADIATION
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RADIATIONS
640105* - Astrophysics &amp; Cosmology- Galaxies