IAU Symposium Abstract S186-067T

Fuelling nuclear starbursts in merging galaxies

J. P. E. Gerritsen1, V. Icke2
1 Kapteyn Instituut, The Netherlands < gerritse@astro.rug.nl >
2 Sterrewacht Leiden, The Netherlands < icke@strw.LeidenUniv.nl >

We use numerical simulations to study the star formation activity in galaxies during interactions and mergers. Emphasis is given to a physical description of star formation and its feedback on the interstellar medium. In particular our star formation recipe uses a Jeans criterion for the gas as a whole, supplemented with an estimate of the cloud collapse timescale. Feedback from star formation is included both as radiative and mechanical heating. We calculate cloud heating due to the global radiation field. We include the mechanical energy released by supernovae and mass loss from massive stars as an extra pressure term working on the gas.

Evolving galaxies with the above mentioned ingredients results in self-regulating star formation with reasonable star formation rates, and a multi-phase interstellar medium, with temperatures between 10K and 107K.

Applying this technique to merging galaxies we find that the star formation activity strongly peaks just before the final merging of the progenitor galaxies, independent of the structure of these progenitors, contrary to previous studies of major mergers which indicate that only galaxies with bulges lead to strong nuclear starbursts (Mihos & Hernquist 1994, ApJ 431, L9). However, it is questionable whether the peak star formation rate can explain the total emission from ultraluminous infrared galaxies.