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Paper: Global versus Nuclear Starbursts
Volume: 249, The Central Kiloparsec of Starbursts and AGN: the La Palma Connection
Page: 475
Authors: Combes, Fran├žoise
Abstract: The strongest starbursts are observed towards galaxy nuclei, or circumnuclear regions. However, in interacting galaxies, star formation is also triggered in overlapping regions far from the nuclei in spiral arms and sometimes in tidal tails. What is the relative importance of these starbursts? What kind of star formation is dominating as a function of redshift? These different starbursts occur in different dynamical conditions (global and local) --- gravitational instabilities, density waves, radial flows, shear, cloud collisions, density accumulations---and they have been investigated with the help of numerical simulations. Gravitational instabilities are necessary to initiate star formation, but they are not sufficient; galactic disks are self-regulated through these instabilities to have their Toomre Q parameter of the order of 1, and thus this criterion is in practice unable to predict the onset of intense star formation. Super star clusters are a characteristic SF mode in starbursts and might be due to the rapid formation of large gas complexes. Star formation can propagate radially inwards, due to gravity torques and gas inflow, but also outwards, due to superwinds and energy outflows: both expanding or collapsing waves are observed in circumnuclear regions. Mergers are more efficient in forming stars at high redshift because of larger gas content and shorter dynamical times. The relation between nuclear starbursts and nuclear activity is based on the same fueling mechanisms, but also on reciprocal triggering and regulations.
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