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Astron. Astrophys. 318, L51-L54 (1997)

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1. Introduction

Our understanding of the links between the gas dynamics and the star formation history in barred galaxies has made remarkable progress in the past ten years, thanks to numerous multi-wavelength observations and N -body simulations with stars, gas and star formation (Mihos & Hernquist 1994; Friedli & Benz 1995).

For instance, the suggestion of Shlosman et al. (1989) that the gas fuelling of the central regions is triggered by dissipation once the bar is formed has been confirmed and the efficiency of the process has been quantified (Friedli & Benz 1993). However, in order to accrete gas on a scale of a few parsec, another mechanism must be invoked, like a secondary bar or a triaxial bulge (Shlosman et al. 1989, 1990). These secondary bars have now been observed in the optical (Wozniak et al. 1995) and near infrared (Friedli et al. 1996) ranges, and in the CO line (Kenney 1996 and references therein). Friedli & Martinet (1993) have shown that double bar structures can transport amounts of gas much closer to the galactic center than simple bars. The gas accretion rate can be very high and may provide a possible mechanism for triggering starbursts.

However, it still remains to be shown that AGN or nuclear starbursts can be fuelled by such mechanisms. Indeed, high resolution observations (Hubble Space Telescope images, CO mappings) are beginning to reveal complex structures that simulations cannot accurately model because of their poor resolution in the innermost region.

In order to shed new light on the relationship between nuclear starbursts and gas dynamics, we decided to combine the properties of molecular clouds with characteristics of the starbursts rarely used in previous studies. In particular, the age of the starburst has so far never been used in practice; it can be now estimated from optical spectroscopy and evolutionary synthesis models.

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© European Southern Observatory (ESO) 1997

Online publication: July 8, 1998