Double-barred galaxies

Free access article

Issue		A&A Volume 415, Number 3, March I 2004


Page(s)		941 - 957
Section		Extragalactic astronomy
DOI		http://dx.doi.org/10.1051/0004-6361:20034408

A&A 415, 941-957 (2004)
DOI: 10.1051/0004-6361:20034408

I. A catalog of barred galaxies with stellar secondary bars and inner disks

Peter Erwin

Instituto de Astrofísica de Canarias, C/ Via Láctea s/n, 38200 La Laguna, Tenerife, Spain
(Received 27 September 2003 / Accepted 7 November 2003)

Abstract
I present a catalog of 67 barred galaxies which contain distinct, elliptical stellar structures inside their bars. Fifty of these are double-barred galaxies: a small-scale, inner or secondary bar is embedded within a large-scale, outer or primary bar. I provide homogenized measurements of the sizes, ellipticities, and orientations of both inner and outer bars, along with global parameters for the galaxies. The other 17 are classified as inner-disk galaxies, where a large-scale bar harbors an inner elliptical structure which is aligned with the galaxy's outer disk. Four of the double-barred galaxies also possess inner disks, located in between the inner and outer bars. While the inner-disk classification is ad-hoc - and undoubtedly includes some inner bars with chance alignments (five such probable cases are identified) - there is good evidence that inner disks form a statistically distinct population, and that at least some are indeed disks rather than bars. In addition, I list 36 galaxies which may be double-barred, but for which current observations are ambiguous or incomplete, and another 23 galaxies which have been previously suggested as potentially being double-barred, but which are probably not. False double-bar identifications are usually due to features such as nuclear rings and spirals being misclassified as bars; I provide some illustrated examples of how this can happen.

A detailed statistical analysis of the general population of double-bar and inner-disk galaxies, as represented by this catalog, will be presented in a companion paper.

Key words: galaxies: structure -- galaxies: elliptical and lenticular, cD -- galaxies: spiral -- galaxies: kinematics and dynamics

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