Double-Barred Galaxies
Abstract
I present a brief review of what is known about double-barred galaxies, where a small ("inner") bar is nested inside a larger ("outer") bar; the review is focused primarily on their demographics and photometric properties. Roughly 20% of S0--Sb galaxies are double-barred; they may be rarer in later Hubble types. Inner bars are typically ~ 500 pc in radius (~ 12% the size of outer bars), but sizes range from ~ 100 pc to > 1 kpc. The structure of at least some inner bars appears very similar to that of outer bars (and single large-scale bars). Direct and indirect evidence all support the hypothesis that inner bars rotate independently of outer bars, although actual pattern speeds for inner bars are poorly constrained. Finally, I note that inner bars do not appear to promote nuclear activity.
Keywords
Cite
@article{arxiv.0908.0909,
title = {Double-Barred Galaxies},
author = {Peter Erwin},
journal= {arXiv preprint arXiv:0908.0909},
year = {2009}
}
Comments
LaTeX, 9 pages, 6 PDF figures (plus small logo PDF figure). To appear in "Tumbling, Twisting, and Winding Galaxies: Pattern Speeds along the Hubble Sequence", E. M. Corsini and V. P. Debattista (eds.), Memorie della Societa` Astronomica Italiana