Embedded protostellar disks around (sub-)solar protostars. I. Disk structure and evolution

Author(s): Eduard Vorobiev
Abstract: We perform a comparative numerical hydrodynamics study of embedded protostellar disks formed as a result of the gravitational collapse of cloud cores of distinct mass (M_cl = 0.2-1.7 M_⊙) and ratio of rotational to gravitational energy β = 0.0028-0.023. An increase in M_cl and/or β leads to the formation of protostellar disks that are more susceptible to gravitational instability. Disk fragmentation occurs in most models but its effect is often limited to the very early stage, with the fragments being either dispersed or driven onto the forming star during tens of orbital periods. Only cloud cores with high enough M_cl or β may eventually form wide-separation binary/multiple systems with low-mass ratios and brown dwarf or sub-solar mass companions. It is feasible that such systems may eventually break up, giving birth to rogue brown dwarfs. Protostellar disks of equal age formed from cloud cores of greater mass (but equal β) are generally denser, hotter, larger, and more massive. On the other hand, protostellar disks formed from cloud cores of higher β (but equal M _cl) are generally thinner and colder but larger and more massive. In all models, the difference between the irradiation temperature and midplane temperature ΔT is small, except for the innermost regions of young disks, dense fragments, and disk's outer edge where Δ T is negative and may reach a factor of 2 or even more. Gravitationally unstable, embedded disks show radial pulsations, the amplitude of which increases along the line of increasing M_cl and β but tends to diminish as the envelope clears. We find that single stars with a disk-to-star mass ratio of order unity can be formed only from high-β cloud cores, but such massive disks are unstable and quickly fragment into binary/multiple systems. A substantial fraction of an embedded disk, especially its inner regions, spiral arms, and dense clumps, may be optically thick, potentially leading to observational underestimates of disk masses in the embedded phase of star formation.
Organisation(s): Department of Astrophysics
Journal: The Astrophysical Journal
Volume: 723
Pages: 1294-1307
No. of pages: 14
ISSN: 0004-637X
DOI: https://doi.org/10.1088/0004-637X/723/2/1294
Publication date: 11-2010
Peer reviewed: Yes
Austrian Fields of Science 2012: 103004 Astrophysics
Keywords
ASJC Scopus subject areas: Nuclear and High Energy Physics, Space and Planetary Science, Astronomy and Astrophysics
Portal url: https://ucrisportal.univie.ac.at/en/publications/f2d84e40-64d1-41a2-8410-02835c407dea

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