Friday, June 28, 2013

1306.6338 (Sami Dib et al.)

Feedback regulated star formation- II. dual constraints on the SFE and the age spread of stars in massive clusters    [PDF]

Sami Dib, Julia Gutkin, Wolfgang Brandner, Enrique Vazquez-Semadeni, Manuel Zamora-Aviles, Shantanu Basu
We show that the termination of the star formation process by winds from massive stars in protocluster forming clumps imposes dual constraints on the star formation efficiencies (SFEs) and stellar age spreads ($\Delta \tau_{*}$). We explore the effects of the wind efficiencies, clump masses, and star formation histories within the clumps on the SFE and age spreads. We considered scenarios in which the core formation efficiency (CFE) per unit time and as a consequence the star formation process is uniform in time and others in which the CFE is accelerated. Models with an accelerated mode of star formation yield shorter age spreads (a few 0.1 Myrs) and typically higher SFE than models in which star formation is uniform in time. We find that the former models reproduce remarkably well the $SFE-\Delta \tau_{*}$ values of starburst clusters such as NGC 3603 YC and Westerlund 1, while the latter describe better the star formation process in lower density environments such as in the Orion Nebula Cluster. We also show that the SFE and $\Delta \tau_{*}$ of massive clusters are expected to be higher in low metallicity environments. This could be tested with future large extragalactic surveys of stellar clusters. We advocate that placing a stellar cluster on the $SFE-\Delta \tau_{*}$ diagram is a powerful method to distinguish the dominant mode of star formation in different environments and a very useful way of testing star formation theories.
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