2 research outputs found
Tree-based solvers for adaptive mesh refinement code FLASH -- III: a novel scheme for radiation pressure on dust and gas and radiative transfer from diffuse sources
Radiation is an important contributor to the energetics of the interstellar
medium, yet its transport is difficult to solve numerically. We present a novel
approach towards solving radiative transfer of diffuse sources via backwards
ray tracing. Here we focus on the radiative transfer of infrared radiation and
the radiation pressure on dust. The new module, \textsc{TreeRay/RadPressure},
is an extension to the novel radiative transfer method \textsc{TreeRay}
implemented in the grid-based MHD code {\sc Flash}. In
\textsc{TreeRay/RadPressure}, every cell and every star particle is a source of
infrared radiation. We also describe how gas, dust and radiation are coupled
via a chemical network. This allows us to compute the local dust temperature in
thermal equilibrium, leading to a significantly improvement over the classical
grey approximation. In several tests, we demonstrate that the scheme produces
the correct radiative intensities as well as the correct momentum input by
radiation pressure. Subsequently, we apply our new scheme to model massive star
formation from a collapsing, turbulent core of 150 . We trace
the effects of both, ionizing and infrared radiation on the dynamics of the
core. We find that the newborn massive star(s) prevent fragmentation in their
proximity through radiative heating. Over time, dust and radiation temperature
equalize, while the gas temperature can be either warmer due to shock heating
or colder due to insufficient dust-gas coupling. Compared to gravity, the
effects of radiation pressure become significant on the core scale only at an
evolved stage.Comment: 25 pages, 19 figures, submitted to MNRA
The impact of episodic outflow feedback on stellar multiplicity and the star formation efficiency
The accretion of material on to young protostars is accompanied by the launching of outflows. Observations show that accretion, and therefore also outflows, are episodic. However, the effects of episodic outflow feedback on the core scale are not well understood. We have performed 88 smoothed particle hydrodynamic simulations of turbulent dense 1M(circle dot) cores to study the influence of episodic outflow feedback on the stellar multiplicity and the star formation efficiency (SFE). Protostars are represented by sink particles, which use a subgrid model to capture stellar evolution, inner-disc evolution, episodic accretion, and the launching of outflows. By comparing simulations with and without episodic outflow feedback, we show that simulations with outflow feedback reproduce the binary statistics of young stellar populations, including the relative proportions of singles, binaries, triples, etc. and the high incidence of twin binaries with q >= 0.95; simulations without outflow feedback do not. Entrainment factors (the ratio between total outflowing mass and initially ejected mass) are typically similar to 7 +/- 2, but can be much higher if the total mass of stars formed in a core is low and/or outflow episodes are infrequent. By decreasing both the mean mass of the stars formed and the number of stars formed, outflow feedback reduces the SFE by about a factor of 2 (as compared with simulations that do not include outflow feedback)