A Detached Protostellar Disk around a ∼0.2 M ⊙ Protostar in a Possible Site of a Multiple Star Formation in a Dynamical Environment in Taurus
Abstract
We report ALMA observations in 0.87 mm continuum and 12CO (J = 3-2) toward a very low-luminosity (<0.1 L ⊙) protostar, which is deeply embedded in one of the densest cores, MC27/L1521F, in Taurus with an indication of multiple star formation in a highly dynamical environment. The beam size corresponds to ∼20 au, and we have clearly detected blueshifted/redshifted gas in 12CO associated with the protostar. The spatial/velocity distributions of the gas show there is a rotating disk with a size scale of ∼10 au, a disk mass of ∼10-4 M ⊙, and a central stellar mass of ∼0.2 M ⊙. The observed disk seems to be detached from the surrounding dense gas, although it is still embedded at the center of the core whose density is ∼106 cm-3. The current low-outflow activity and the very low luminosity indicate that the mass accretion rate onto the protostar is extremely low in spite of a very early stage of star formation. We may be witnessing the final stage of the formation of ∼0.2 M ⊙ protostar. However, we cannot explain the observed low luminosity with the standard pre-main-sequence evolutionary track unless we assume cold accretion with an extremely small initial radius of the protostar (∼0.65 {R}⊙ ). These facts may challenge our current understanding of the low mass star formation, in particular the mass accretion process onto the protostar and the circumstellar disk.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 2017
- DOI:
- 10.3847/1538-4357/aa8e9e
- arXiv:
- arXiv:1709.07113
- Bibcode:
- 2017ApJ...849..101T
- Keywords:
-
- circumstellar matter;
- ISM: kinematics and dynamics;
- stars: formation;
- stars: individual: L1521F-IRS;
- stars: low-mass;
- stars: protostars;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 9 pages, 4 figures, accepted for publication in The Astrophysical Journal