EDP Sciences
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Volume 391, Number 3, September I 2002
Page(s) 823 - 831
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20020875

A&A 391, 823-831 (2002)
DOI: 10.1051/0004-6361:20020875

More evidence for hidden spiral and bar features in bright early-type dwarf galaxies

F. D. Barazza1, B. Binggeli1 and H. Jerjen2

1  Astronomisches Institut, Universität Basel, Venusstrasse 7, 4102 Binningen, Switzerland
2  Research School of Astronomy and Astrophysics, The Australian National University, Mt Stromlo Observatory, Cotter Road, Weston ACT 2611, Australia

(Received 25 February 2002 / Accepted 31 May 2002)

Following the discovery of spiral structure in IC 3328 (Jerjen et al. 2000), we present further evidence that a sizable fraction of bright early-type dwarfs in the Virgo cluster are genuine disk galaxies, or are hosting a disk component. Among a sample of 23 nucleated dwarf ellipticals and dS0s observed with the Very Large Telescope in B and R, we found another four systems exhibiting non-axisymmetric structures, such as a bar and/or spiral arms, indicative of a disk (IC 0783, IC 3349, NGC 4431, IC 3468). Particularly remarkable are the two-armed spiral pattern in IC 0783 and the bar and trailing arms in NGC 4431. For both galaxies the disk nature has recently been confirmed by a rotation velocity measurement (Simien & Prugniel 2002). Our photometric search is based on a Fourier decomposition method and a specific version of unsharp masking. Some "early-type" dwarfs in the Virgo cluster seem to be former late-type galaxies which were transformed to early-type morphology, e.g. by "harassment", during their infall to the cluster, while maintaining part of their disk structure.

Key words: galaxies: general -- galaxies: fundamental parameters -- galaxies: photometry -- galaxies: structure

Offprint request: F. D. Barazza, barazza@astro.unibas.ch

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