A Detached Protostellar Disk around a ∼0.2 M o Protostar in a Possible Site of a Multiple Star Formation in a Dynamical Environment in Taurus

Kazuki Tokuda, Toshikazu Onishi, Kazuya Saigo, Takashi Hosokawa, Tomoaki Matsumoto, Shu Ichiro Inutsuka, Masahiro N. Machida, Kengo Tomida, Masanobu Kunitomo, Akiko Kawamura, Yasuo Fukui, Kengo Tachihara

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Abstract

We report ALMA observations in 0.87 mm continuum and 12CO (J = 3-2) toward a very low-luminosity (<0.1 L o) 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 o, and a central stellar mass of ∼0.2 M o. 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 o 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 ). 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.

Original languageEnglish
Article number101
JournalAstrophysical Journal
Volume849
Issue number2
DOIs
Publication statusPublished - Nov 10 2017

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All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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