Modelling accretion in protobinary systems

Bate, Matthew R.; Bonnell, Ian A.; Price, Nigel M.

doi:10.1093/mnras/277.2.362

Cited by 876 publications

(1,016 citation statements)

References 27 publications

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“…On scales below a few parsecs, the most commonly adopted sub-resolution model is the 'sink particle' approach (Bate, Bonnell & Price 1995;Li, Mac Low & Klessen 2005;Federrath et al 2010;Hubber, Walch & Whitworth 2013;Gatto et al 2017). The idea is that when a region of gas is so gravitationally unstable that it will inevitably collapse and form stars, one can simply convert it into a 'sink particle' which only interacts gravitationally but not hydrodynamically with the rest of the system.…”

Section: Star Formationmentioning

confidence: 99%

Variable interstellar radiation fields in simulated dwarf galaxies: supernovae versus photoelectric heating

Naab

Glover

et al. 2017

Monthly Notices of the Royal Astronomical Society

129

222

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We present high-resolution hydrodynamical simulations of isolated dwarf galaxies including self-gravity, non-equilibrium cooling and chemistry, interstellar radiation fields (IRSF) and shielding, star formation, and stellar feedback. This includes spatially and temporally varying photoelectric (PE) heating, photoionization, resolved supernova (SN) blast waves and metal enrichment. A new flexible method to sample the stellar initial mass function allows us to follow the contribution to the ISRF, the metal output and the SN delay times of individual massive stars. We find that SNe play the dominant role in regulating the global star formation rate, shaping the multi-phase interstellar medium (ISM) and driving galactic outflows. Outflow rates (with massloading factors of a few) and hot gas fractions of the ISM increase with the number of SNe exploding in low-density environments where radiative energy losses are low. While PE heating alone can suppress star formation slightly more (a factor of a few) than SNe alone can do, it is unable to drive outflows and reproduce the multi-phase ISM that emerges naturally when SNe are included. These results are in conflict with recent results of Forbes et al. who concluded that PE heating is the dominant process suppressing star formation in dwarfs, about an order of magnitude more efficient than SNe. Potential origins for this discrepancy are discussed. In the absence of SNe and photoionization (mechanisms to disperse dense clouds), the impact of PE heating is highly overestimated owing to the (unrealistic) proximity of dense gas to the radiation sources. This leads to a substantial boost of the infrared continuum emission from the UV-irradiated dust and a far infrared line-to-continuum ratio too low compared to observations. Though sub-dominant in regulating star formation, the ISRF controls the abundance of molecular hydrogen via photodissociation.

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Section: Star Formationmentioning

confidence: 99%

Variable interstellar radiation fields in simulated dwarf galaxies: supernovae versus photoelectric heating

Naab

Glover

et al. 2017

Monthly Notices of the Royal Astronomical Society

129

222

View full text Add to dashboard Cite

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“…The fluid equations may then be reformulated as sums over the particles by treating the density, internal energy and so on as interpolated quantities. The simulations shown later in this paper were performed with the SPH code SPHNG (Bate, Bonnell & Price 1995;Price & Monaghan 2007). This code allows for the creation of sink particles which represent stars.…”

Section: Methodsmentioning

confidence: 99%

“…The criteria for creation are as described in Bate et al (1995); a brief description follows here. A gas particle being tested had to exceed a critical density set to 10 8 ρ0 = 1.29 × 10 −13 g cm −3 , and all its neighbours (gas particles within the kernel) had to be within a distance of 0.01 pc.…”

Section: Run Namementioning

confidence: 99%

Can the removal of molecular cloud envelopes by external feedback affect the efficiency of star formation?

Lucas¹,

Bonnell²,

Forgan³

2017

Mon. Not. R. Astron. Soc.

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We investigate how star formation efficiency can be significantly decreased by the removal of a molecular cloud's envelope by feedback from an external source. Feedback from star formation has difficulties halting the process in dense gas but can easily remove the less dense and warmer envelopes where star formation does not occur. However, the envelopes can play an important role keeping their host clouds bound by deepening the gravitational potential and providing a constraining pressure boundary. We use numerical simulations to show that removal of the cloud envelopes results in all cases in a fall in the star formation efficiency (SFE). At 1.38 free-fall times our 4 pc cloud simulation experienced a drop in the SFE from 16 to six percent, while our 5 pc cloud fell from 27 to 16 per cent. At the same time, our 3 pc cloud (the least bound) fell from an SFE of 5.67 per cent to zero when the envelope was lost. The star formation efficiency per free-fall time varied from zero to ≈ 0.25 according to α, defined to be the ratio of the kinetic plus thermal to gravitational energy, and irrespective of the absolute star forming mass available. Furthermore the fall in SFE associated with the loss of the envelope is found to even occur at later times. We conclude that the SFE will always fall should a star forming cloud lose its envelope due to stellar feedback, with less bound clouds suffering the greatest decrease.

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“…It is adequate for the problem considered here, where we follow the evolution of highly nonlinear density fluctuations created by supersonic turbulence. We replace the central high-density regions of collapsing gas cores by sink particles (Bate et al 1995). These particles have the ability to accrete gas from their surroundings while keeping track of mass and momentum.…”

Section: Numerical Approachmentioning

confidence: 99%

The Stellar Mass Spectrum from Non-Isothermal Gravoturbulent Fragmentation

Jappsen

Klessen

Larson

et al. 2005

The Initial Mass Function 50 Years Later

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Identifying the processes that determine the initial mass function of stars (IMF) is a fundamental problem in star formation theory. One of the major uncertainties is the exact chemical state of the star forming gas and its influence on the dynamical evolution. Most simulations of star forming clusters use an isothermal equation of state (EOS). We address these issues and study the effect of a piecewise polytropic EOS on the formation of stellar clusters in turbulent, selfgravitating molecular clouds using three-dimensional, smoothed particle hydrodynamics simulations. In these simulations stars form via a process we call gravoturbulent fragmentation, i.e., gravitational fragmentation of turbulent gas.To approximate the results of published predictions of the thermal behavior of collapsing clouds, we increase the polytropic exponent γ from 0.7 to 1.1 at some chosen density n c , which we vary from from 4.3 × 10 4 cm −3 to 4.3 × 10 7 cm −3 . The change of thermodynamic state at n c selects a characteristic mass scale for fragmentation M ch , which we relate to the peak of the observed IMF. We find a relation M ch ∝ n −0.5±0.1 c . Our investigation supports the idea that the distribution of stellar masses largely depends on the thermodynamic state of the star-forming gas. The thermodynamic state of interstellar gas is a result of the balance between heating and cooling processes, which in turn are determined by fundamental atomic and molecular physics and by chemical abundances. Given the abundances, the derivation of a characteristic stellar mass may thus be based on universal quantities and constants.

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Modelling accretion in protobinary systems

Cited by 876 publications

References 27 publications

Variable interstellar radiation fields in simulated dwarf galaxies: supernovae versus photoelectric heating

Variable interstellar radiation fields in simulated dwarf galaxies: supernovae versus photoelectric heating

Can the removal of molecular cloud envelopes by external feedback affect the efficiency of star formation?

The Stellar Mass Spectrum from Non-Isothermal Gravoturbulent Fragmentation

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