Protostellar mass accretion rates from gravoturbulent fragmentation

Abstract

Abstract. We analyse protostellar mass accretion ratesṀ from numerical models of star formation based on gravoturbulent fragmentation, considering a large number of different environments. To within one order of magnitude,Ṁ ≈ M J /τ ff with M J being the mean thermal Jeans mass and τ ff the corresponding free-fall time. However, mass accretion rates are highly timevariant, with a sharp peak shortly after the formation of the protostellar core. We present an empirical exponential fit formula to describe the time evolution of the mass accretion and discuss the resulting fit parameters. There is a positive correlation between the peak accretion rate and the final mass of the protostar. We also investigate the relation ofṀ with the turbulent flow velocity as well as with the driving wavenumbers in different environments. We then compare our results with other theoretical models of star formation and with observational data.

Which Are the Youngest Protostars? Determining Properties of Confirmed and Candidate Class 0 Sources by Broadband Photometry

“…Also there is no restriction on the final mass as in the other models. Further, the assumed mass accretion rates are very similar to accretion rates obtained by hydrodynamical simulations of star formation (e.g., Klessen 2001;Schmeja & Klessen 2004). Hence, it is worth to investigate the resulting final mass function obtained for our sources using this model.…”

“…(1) One might be found in the mass accretion rates obtained by Klessen (2001) and Schmeja & Klessen (2004). It turns out that their accretion rates on average show a time evolution similar to the one used in the model of Smith (1998Smith ( , 2000Smith ( , 2002.…”

“…While the overall decline with time has substantial observational support (Calvet et al 2000), the particular behavior is unclear. Analytical and numerical models reproduce both, exponential decline (Shu et al 2004) or welldefined early peaks followed by a fall-off (Schmeja & Klessen 2004). The usage of T bol and L bol as input parameters (Smith 1998(Smith , 2000(Smith , 2002Myers et al 1998) will lead to uncertainties since both depend on the viewing angle, in contrast to the envelope mass , which is inferred from optically thin dust emission.…”

Physical Processes in the Interstellar Medium

“…The shorter the time between shock passages, the less likely these fluctuations are to survive. Hence, the timescale and efficiency of protostellar core formation depend strongly on the wavelength and strength of the driving source Heitsch et al, 2001a;Vázquez-Semadeni et al, 2003;Mac Low & Klessen, 2004;Krumholz & McKee, 2005;Ballesteros-Paredes et al, 2007;McKee & Ostriker, 2007), and accretion histories of individual protostars are strongly time-varying (Klessen, 2001a;Schmeja & Klessen, 2004).…”

Changing Structures in Galactic Star Clusters

“…We performed numerical SPH simulations of the fragmentation and collapse of turbulent, self-gravitating gas clouds and the resulting formation and evolution of a star cluster as described in Schmeja & Klessen (2004). We investigated models with different turbulent velocities and driving scales and analysed the temporal evolution of the cluster structure.…”