Journal Article

Constraining the formation of inner bars: photometry, kinematics and stellar populations in NGC 357*

A. de Lorenzo-Cáceres, A. Vazdekis, J. A. L. Aguerri, E. M. Corsini and Victor P. Debattista

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 420, issue 2, pages 1092-1106
Published in print February 2012 | ISSN: 0035-8711
Published online January 2012 | e-ISSN: 1365-2966 | DOI: https://dx.doi.org/10.1111/j.1365-2966.2011.20100.x
Constraining the formation of inner bars: photometry, kinematics and stellar populations in NGC 357*

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Double-barred galaxies are common in the local Universe, with approximately one-third of barred spirals hosting a smaller, inner bar. Nested bars have been proposed as a mechanism to transport gas to the very central regions of the galaxy, trigger star formation and contribute to the growth of the bulge. To test this idea, we perform for the first time a detailed analysis of the photometry, kinematics and stellar populations of a double-barred galaxy: NGC 357. We find that this galaxy is either hosting a pseudo-bulge or a classical bulge together with an inner disc. We compare the relative mean luminosity-weighted age, metallicity and α-enhancement between the (pseudo-)bulge, inner bar and outer bar, finding that the three structures are nearly coeval and old. Moreover, the bulge and inner bar present the same metallicity and overabundance, whereas the outer bar tends to be less metal rich and more α-enhanced. These results point out that, rather than the classical secular scenario in which gas and star formation play a major role, the redistribution of the existing stars is driving the formation of the inner structures.

Keywords: galaxies: bulges; galaxies: evolution; galaxies: individual: NGC 357; galaxies: kinematics and dynamics; galaxies: photometry; galaxies: structure

Journal Article.  11528 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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