Protostar Mass due to Infall and Dispersal

Myers, Philip C.

doi:10.1086/591664

Cited by 39 publications

(40 citation statements)

References 83 publications

(144 reference statements)

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“…For our simulations, it appears that unless cores are formed with very large density contrasts relative to their surroundings, ambient gas will play an important and ongoing role in the core's dynamics. This is in line with models that attempt to consider more continuous distributions of variables between core and environment (Myers 2008 …”

Section: Discussionsupporting

confidence: 81%

On the Role of Ambient Environments in the Collapse of Bonnor-Ebert Spheres

Kaminski

Frank

Carroll

et al. 2014

ApJ

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We consider the interaction between a marginally stable Bonnor-Ebert (BE) sphere and the surrounding ambient medium. In particular, we explore how the infall from an evolving ambient medium can trigger the collapse of the sphere using three-dimensional adaptive mesh refinement simulations. We find the resulting collapse dynamics to vary considerably with ambient density. In the highest ambient density cases, infalling material drives a strong compression wave into the cloud. It is the propagation of this wave through the cloud interior that triggers the subsequent collapse. For lower ambient densities, we find the main trigger of collapse to be a quasistatic adjustment of the BE sphere to gravitational settling of the ambient gas. In all cases, we find that the classic "outside-in" collapse mode for super-critical BE spheres is recovered before a protostar (i.e., sink particle) forms. Our work supports scenarios in which BE dynamics naturally begins with either a compression wave or infall dominated phase, and only later assumes the usual outside-in collapse behavior.

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Section: Discussionsupporting

confidence: 81%

On the Role of Ambient Environments in the Collapse of Bonnor-Ebert Spheres

Kaminski

Frank

Carroll

et al. 2014

ApJ

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“…The observed increasing opening angles of outflows with increasing age of the protostar has been interpreted as evidence for the erosion of the protostellar envelope by the outflow (Velusamy & Langer 1998;Arce & Sargent 2006) in part explaining the observed shift in the peak between the core and initial mass function (e.g., Myers 2008). In the models of Visser et al (2009) and shown in Fig.…”

Section: Constraints On Evolutionary Modelsmentioning

confidence: 89%

PROSAC: a submillimeter array survey of low-mass protostars

Jørgensen¹,

Dishoeck

Visser³

et al. 2009

A&A

265

447

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Context. The key question about early protostellar evolution is how matter is accreted from the large-scale molecular cloud, through the circumstellar disk onto the central star. Aims. We constrain the masses of the envelopes, disks, and central stars of a sample of low-mass protostars and compare the results to theoretical models for the evolution of young stellar objects through the early protostellar stages. Methods. A sample of 20 Class 0 and I protostars has been observed in continuum at (sub)millimeter wavelengths at high angular resolution (typically 2 ) with the submillimeter array. Using detailed dust radiative transfer models of the interferometric data, as well as single-dish continuum observations, we have developed a framework for disentangling the continuum emission from the envelopes and disks, and from that estimated their masses. For the Class I sources in the sample HCO + 3-2 line emission was furthermore observed with the submillimeter array. Four of these sources show signs of Keplerian rotation, making it possible to determine the masses of the central stars. In the other sources the disks are masked by optically thick envelope and outflow emission. Results. Both Class 0 and I protostars are surrounded by disks with typical masses of about 0.05 M , although significant scatter is seen in the derived disk masses for objects within both evolutionary stages. No evidence is found for a correlation between the disk mass and evolutionary stage of the young stellar objects. This contrasts the envelope mass, which decreases sharply from ∼1 M in the Class 0 stage to < ∼ 0.1 M in the Class I stage. Typically, the disks have masses that are 1-10% of the corresponding envelope masses in the Class 0 stage and 20-60% in the Class I stage. For the Class I sources for which Keplerian rotation is seen, the central stars contain 70-98% of the total mass in the star-disk-envelope system, confirming that these objects are late in their evolution through the embedded protostellar stages, with most of the material from the ambient envelope accreted onto the central star. Theoretical models tend to overestimate the disk masses relative to the stellar masses in the late Class I stage. Conclusions. The results argue in favor of a picture in which circumstellar disks are formed early during the protostellar evolution (although these disks are not necessarily rotationally supported) and rapidly process material accreted from the larger scale envelope onto the central star.

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“…A difficulty with this model is that the accretion continues indefinitely. More recently, Myers (2008) has included a model for a time-dependent dispersal of the protostellar core by protostellar outflows. If the dispersal time is sufficiently short, the protostellar mass converges to a well-defined value.…”

Section: Tapered Accretionmentioning

confidence: 99%

The Protostellar Mass Function

McKee

Offner

2010

ApJ

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The protostellar mass function (PMF) is the present-day mass function of the protostars in a region of star formation. It is determined by the initial mass function weighted by the accretion time. The PMF thus depends on the accretion history of protostars and in principle provides a powerful tool for observationally distinguishing different protostellar accretion models. We consider three basic models here: the isothermal sphere model, the turbulent core model, and an approximate representation of the competitive accretion model. We also consider modified versions of these accretion models, in which the accretion rate tapers off linearly in time. Finally, we allow for an overall acceleration in the rate of star formation. At present, it is not possible to directly determine the PMF since protostellar masses are not currently measurable. We carry out an approximate comparison of predicted PMFs with observation by using the theory to infer the conditions in the ambient medium in several star-forming regions. Tapered and accelerating models generally agree better with observed star formation times than models without tapering or acceleration, but uncertainties in the accretion models and in the observations do not allow one to rule out any of the proposed models at present. The PMF is essential for the calculation of the protostellar luminosity function, however, and this enables stronger conclusions to be drawn.

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Protostar Mass due to Infall and Dispersal

Cited by 39 publications

References 83 publications

On the Role of Ambient Environments in the Collapse of Bonnor-Ebert Spheres

On the Role of Ambient Environments in the Collapse of Bonnor-Ebert Spheres

PROSAC: a submillimeter array survey of low-mass protostars

The Protostellar Mass Function

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