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Date and Time of the Query: 2019-04-25 T10:26:25 PDT
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For refcode 2001MNRAS.326.1076D:
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Copyright by Royal Astronomical Society. 2001MNRAS.326.1076D The evolution and star formation of dwarf galaxies in the Fornax Cluster M. J. Drinkwater, M. D. Gregg, B. A. Holman and M. J. I. Brown Accepted 2001 May 8. Received 2001 April 11; in original form 2001 January 8 ABSTRACT We present the results of a spectroscopic survey of 675 bright (16.5 < b_j_ < 18) galaxies in a 6^deg^ field centred on the Fornax cluster with the FLAIR-II spectrograph on the UK Schmidt Telescope. Three galaxy samples were observed: compact galaxies to search for new blue compact dwarfs, candidate M 32-like compact dwarf ellipticals, and a subset of the brightest known cluster members in order to study the cluster dynamics. We measured redshifts for 516 galaxies, of which 108 were members of the Fornax Cluster. Defining dwarf galaxies to be those with b_j_ >= 15 (M_B_ >= -16.5), there are a total of 62 dwarf cluster galaxies in our sample. Nine of these are new cluster members previously misidentified as background galaxies. The cluster dynamics show that the dwarf galaxies are still falling into the cluster whereas the giants are virialized. We classified the observed galaxies as late-type if we detected H{alpha} emission at an equivalent width greater than 1 A. The spectra were obtained through fixed apertures, so they reflect activity in the galaxy cores, but this does not significantly bias the classifications of the compact dwarfs in our sample. The new classifications reveal a higher rate of star formation among the dwarf galaxies than suggested by morphological classification: 35 per cent have significant H{alpha} emission indicative of star formations but only 19 per cent were morphologically classified as late-types. The star-forming dwarf galaxies span the full range of physical sizes and we find no evidence in our data for a distinct class of star-forming blue compact dwarf (BCD) galaxy. The distribution of scale sizes is consistent with evolutionary processes which transform late-type dwarfs to early-type dwarfs. The fraction of dwarfs with active star formation drops rapidly towards the cluster centre: this is the usual density-morphology relation confirmed here for dwarf galaxies. The star-forming dwarfs are concentrated in the outer regions of the cluster, the most extreme in an infalling subcluster. We estimate gas depletion time-scales for five dwarfs with detected H I emission: these are long (of order 10^10^ yr), indicating that an active gas removal process must be involved if they are transformed into gas-poor dwarfs as they fall further into the cluster. Finally, in agreement with our previous results, we find no compact dwarf elliptical (M 32-like) galaxies in the Fornax Cluster. Key words: stars: formation - galaxies: dwarf - galaxies: evolution - galaxies: clusters: individual: Fornax.
Retrieve 527 NED objects in this reference.
Please click here for ADS abstract

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