Apparent Disk-mass Reduction and Planetisimal Formation in Gravitationally Unstable Disks in Class 0/I Young Stellar Objects
Abstract
We investigate the dust structure of gravitationally unstable disks undergoing mass accretion from the envelope, envisioning its application to Class 0/I young stellar objects (YSOs). We find that the dust disk quickly settles into a steady state and that, compared to a disk with interstellar medium (ISM) dust-to-gas mass ratio and micron-sized dust, the dust mass in the steady state decreases by a factor of 1/2 to 1/3, and the dust thermal emission decreases by a factor of 1/3 to 1/5. The latter decrease is caused by dust depletion and opacity decrease owing to dust growth. Our results suggest that the masses of gravitationally unstable disks in Class 0/I YSOs are underestimated by a factor of 1/3 to 1/5 when calculated from the dust thermal emission assuming an ISM dust-to-gas mass ratio and micron-sized dust opacity, and that a larger fraction of disks in Class 0/I YSOs is gravitationally unstable than was previously believed. We also investigate the orbital radius {r}{{P}} within which planetesimals form via coagulation of porous dust aggregates and show that {r}{{P}} becomes ∼20 au for a gravitationally unstable disk around a solar mass star. Because {r}{{P}} increases as the gas surface density increases and a gravitationally unstable disk has maximum gas surface density, {r}{{P}}∼ 20 {au} is the theoretical maximum radius for planetesimal formation. We suggest that planetesimal formation in the Class 0/I phase is preferable to that in the Class II phase because a large amount of dust is supplied by envelope-to-disk accretion.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 2017
- DOI:
- 10.3847/1538-4357/aa6081
- arXiv:
- arXiv:1608.03015
- Bibcode:
- 2017ApJ...838..151T
- Keywords:
-
- protoplanetary disks;
- stars: formation;
- stars: protostars;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- 25 pages, 13 figures, accepted for publication in ApJ. The reference is modified. Comments are welcome