EPoS Contribution
EPoS Contribution
Stochastic grain heating and mid-infrared emission in protostellar cores

Yaroslav Pavlyuchenkov
Institute of Astronomy, Russian Academy of Sciences, Moscow, Russia
Stochastic heating of small grains is often mentioned as a primary cause of large infrared (IR) fluxes from star-forming galaxies, e.g. at 24\,$\mu$m. If the mechanism does work at a galaxy-wide scale, it should show up at smaller scales as well. We calculate temperature probability density distributions within a model protostellar core for four dust components: large silicate and graphite grains, small graphite grains, and polycyclic aromatic hydrocarbon particles. The corresponding spectral energy distributions are calculated and compared with observations of a representative infrared dark cloud core. We show that stochastic heating, induced by the standard interstellar radiation field, cannot explain high mid-IR emission toward the centre of the core. In order to reproduce the observed emission from the core projected centre, in particular, at 24 micron, we need to increase the ambient radiation field by a factor of about 70. However, the model with enhanced radiation field predicts even higher intensities at the core periphery, giving it a ring-like appearance, that is not observed. We discuss possible implications of this finding and also discuss a role of other non-radiative dust heating processes.
Caption: Results of RT simulations for the model protostellar core. Left: shown with colour is logarithm of the normalized temperature probability distribution P*(T) for PAH particles. Right: spectral energy distribution toward the position offset by 1" from the core centre. Spectra are computed separately for large silicates (red lines), large graphite grains (thick blue lines), small graphite grains (thin blue lines), and PAH particles (red lines). The emergent spectrum with all dust populations taken into account is shown with solid black line. The background interstellar radiation is shown with black dashed line. Filled circles indicate observed values for the IRDC 321 core.
Dmitri Wiebe, INASAN, Russia
Thomas Henning, MPIA, Germany
Key publication