Fueling and morphology of central starbursts.pdf

a r X i v : a s t r o - p h / 0 4 1 2 1 6 2 v 2 1 7 J a n 2 0 0 5 Fueling and morphology of central starbursts Johan H. Knapen Centre for Astrophysics Research, University of Hertfordshire, Hatfield, Herts AL10 9AB, U.K. Abstract. Of the mechanisms proposed to bring gaseous fuel into the central starburst regions of a galaxy, non-axisymmetries in the gravitational potential set up by interactions or by bars are among the most promising. Nevertheless, direct observational evidence for a connection between interactions and bars on the one hand, and starburst (as well as AGN) activity on the other, remains patchy. These general issues are reviewed before proceeding to discuss, within this context, massive star formation in the circumnuclear regions of spiral galaxies, in particular star-forming nuclear rings and pseudo- rings. Such rings are common, and are closely linked to the dynamics of their host galaxy, which in almost all cases is barred. The possible existence of a population of nuclear rings on scales which are too small for detection with standard ground- or even space-based techniques will be discussed. INTRODUCTION Some of the most important open questions relating to starburst activity in galaxies are what combination of physical conditions leads to the triggering of the burst, and how long a starburst can be sustained. These questions are intimately related to another one, namely how a starburst is fueled. One obvious prerequisite for the occurrence of a starburst is the availability of sufficient gaseous fuel for the much enhanced star formation, of the right properties, e.g., temperature, density, and dynamics, and at the right location at the right time. Important parallels exist between the problems of fueling starbursts and active galactic nuclei (AGN), at least low-level AGN such as Seyferts and LINERs. Both will need a well-regulated supply of gas being fed into the nuclear region of a galaxy from its disk, and both can be expected to be corre