Feedback Regulated Star Formation Sami Dib Imperial College, London, UK
I will summarise results from a model which describes star formation in protocluster clumps of different metallicities. In this model, gravitationally bound cores form uniformly in the clump following a prescribed core formation efficiency per unit time. After a contraction timescale which is equal to a few times their free-fall times, the cores collapse into stars and populate the IMF. Winds from the newly formed OB stars remove gas from the clump until core and star formation are quenched. The power of the radiation driven winds has a strong dependence on metallicity and increases with increasing metallicity. Thus, winds from stars in the high metallicity models lead to a rapid evacuation of the gas from the protocluster clump and to a reduced star formation efficiency, SFE_{exp}, as compared to their low metallicity counterparts. By combining SFE_{exp} with the timescales on which gas expulsion occurs, we derive the metallicity dependent star formation rate per unit time in this model as a function of the gas surface density Sigma_{g}. This is combined with the molecular gas fraction in order to derive the dependence of the surface density of star formation Sigma_{SFR} on Sigma_{g} in galactic disks. This feedback regulated model of star formation reproduces very well the observed star formation laws extending from low gas surface densities up to the starburst regime. Furthermore, the results show a dependence of Sigma_{SFR} on metallicity over the entire range of gas surface densities.
Caption: Star formation laws in the feedback-regulated star formation model for selected values of the metallicity in the range $Z/Zsolar=[0.1,2]$. Overplotted to the models are the normal and starburst galaxies data of Kennicutt (1998) and the combined sub-kpc data (4478 subregions) for 11 nearby galaxies from Bigiel et al. (2008,2010). The Bigiel et al. data is shown in the form of a 2D histogram with the colour coding corresponding, from the lighter to the darker colours to the 1,5,10,20, and 30 contour levels.
Collaborators: Subhanjoy Mohanty (Imperial College London, UK) Jonathan Braine (LAB, Bordeaux Observatory, France) Laurent Piau (LATMOS, France)	Key publication