EMBEDDED PROTOSTELLAR DISKS AROUND (SUB-)SOLAR PROTOSTARS. I. DISK STRUCTURE AND EVOLUTION
- Institute for Computational Astrophysics, Saint Mary's University, Halifax, B3H 3C3 (Canada)
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{sub cl} = 0.2-1.7 M{sub sun}) and ratio of rotational to gravitational energy {beta} = 0.0028-0.023. An increase in M{sub cl} and/or {beta} 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{sub cl} or {beta} 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 {beta}) are generally denser, hotter, larger, and more massive. On the other hand, protostellar disks formed from cloud cores of higher {beta} (but equal M{sub cl}) are generally thinner and colder but larger and more massive. In all models, the difference between the irradiation temperature and midplane temperature utriT is small, except for the innermost regions of young disks, dense fragments, and disk's outer edge where utriT 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{sub cl} and {beta} 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-{beta} 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.
- OSTI ID:
- 21471271
- Journal Information:
- Astrophysical Journal, Vol. 723, Issue 2; Other Information: DOI: 10.1088/0004-637X/723/2/1294; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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