Volume 409, Number 2, October II 2003
|Page(s)||485 - 490|
|Published online||17 November 2003|
Evidence for a large stellar bar in the Low Surface Brightness galaxy UGC 7321 *
Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain e-mail: pohlen,firstname.lastname@example.org
2 Astronomical Institute, Ruhr-Universität Bochum, 44780 Bochum, Germany e-mail: email@example.com
3 Department of Computer Science, FernUniversität Hagen, 58084 Hagen, Germany e-mail: Rainer.Luetticke@FernUni-Hagen.de
Corresponding author: M. Pohlen, firstname.lastname@example.org
Accepted: 7 July 2003
Late-type spiral galaxies are thought to be the dynamically simplest type of disk galaxy and our understanding of their properties plays a key role in galaxy formation and evolution scenarios. The low surface brightness (LSB) galaxy UGC 7321, a nearby, isolated, “superthin” edge-on galaxy, is an ideal object to study these purely disk-dominated bulge-less galaxies. Although late type spirals are believed to exhibit the simplest possible structure, even prior observations showed deviations from a pure single component exponential disk in the case of UGC 7321. We present for the first time photometric evidence for peanut-shaped outer isophotes from a deep optical (R-band) image of UGC 7321. Observations and dynamical modeling suggest that boxy/peanut-shaped (b/p) bulges in general form through the buckling instability in bars of the parent galaxy disks. Together with recent HI observations supporting the presence of a stellar bar in UGC 7321, this could be the earliest known case of the buckling process during the evolutionary life of a LSB galaxy, whereby material in the disk-bar has started to be pumped up above the disk, but a genuine bulge has not yet formed.
Key words: galaxies: spiral / galaxies: structure / galaxies: fundamental parameters / galaxies: evolution / galaxies: peculiar / galaxies: individual: UGC 7321
© ESO, 2003
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