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Astron. Astrophys. 326, 449-464

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Star formation in bar environments

I. Morphology, star formation rates and general properties

P. Martin1 and D. Friedli2,3

1European Southern Observatory, Casilla 19001, Santiago 19, Chile (e-mail: pmartin@sc.eso.org)
2Département de physique and OMM, Université Laval, Ste-Foy, Québec, G1K 7P4, Canada (e-mail: dfriedli@phy.ulaval.ca)
3Geneva Observatory, CH-1290 Sauverny, Switzerland

Received 19 March 1997 / Accepted 5 May 1997


A study of the morphological properties and star formation rates (SFRs) of HII regions located along the bars of a sample of eleven late-type barred systems is presented and compared with numerical simulations. According to the relative intensity of star formation along the bar with respect to that of the nuclear region, three types of distributions are observed. They may be related to the age of the bar. Other important characteristics include angular misalignments (up to 15FORMULA ) between the stellar bar and the ''HFORMULA bar'', a correlation between the location of the HII regions and dust lanes in certain bars (mostly early-type spirals), and a difference in axial ratio and length between stellar and HFORMULA bars. A wide range of SFRs (from 0.03 to FORMULA ) is observed, and star formation is generally highly asymmetric with respect to the bar minor axis. All these features can be reproduced in numerical models provided that the global mechanical energy release remains low (but non-zero). In NGC 7479, the total gas-to-star transformation efficiency inside the bar is estimated at about 0.26, meaning that, at present, maybe as nearly as 75% of the gas flowing into the bar region is not transformed into stars.

Key words: galaxies: evolution - galaxies: ism - galaxies: kinematics and dynamics - galaxies: spiral - galaxies: structure

Send offprint requests to: P. Martin

© European Southern Observatory (ESO) 1997

Online publication: September 18, 1997
Last change: October 15, 1997