Oral Presentation

Origin of very large grains in dense molecular cores and protostellar envelopes

Author(s): Hiroyuki Hirashita (ASIAA), Yi Hang Valerie Wong (NTHU), Zhi-Yun Li (University of Virginia)

Presenter: Hiroyuki Hirashita (ASIAA)

There are some pieces of observational evidence that dust grains grow in dense molecular cores up to micron sizes (coreshine; excess of scattering at micron wavelengths) and mm sizes (excess of dust emissivity at mm wavelengths). In this presentation, I will talk about our theoretical efforts of explaining grain growth up to those sizes in dense molecular cores and protostellar envelopes. We show that it is possible to form micron-sized dust in dense molecular cores by coagulation if such dense clouds are sustained for several free-fall times (Hirashita and Li 2013). However, it is extremely difficult to coagulate grains up to mm sizes in dense cores and protostellar envelopes because of their low densities. Therefore, we proposed a scenario in which large grains are supplied from the inner dense part of the protostellar environment (Wong et al. 2016). I will also propose some possible observational plans for Band 1. Statistical and sensitive observations by Band 1 are crucial to test the origin of mm grains in protostellar envelopes.