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Title: Grand-design Spiral Arms in a Young Forming Circumstellar Disk

Abstract

We study formation and long-term evolution of a circumstellar disk in a collapsing molecular cloud core using a resistive magnetohydrodynamic simulation. While the formed circumstellar disk is initially small, it grows as accretion continues, and its radius becomes as large as 200 au toward the end of the Class-I phase. A pair of grand-design spiral arms form due to gravitational instability in the disk, and they transfer angular momentum in the highly resistive disk. Although the spiral arms disappear in a few rotations as expected in a classical theory, new spiral arms form recurrently as the disk, soon becoming unstable again by gas accretion. Such recurrent spiral arms persist throughout the Class-0 and I phases. We then perform synthetic observations and compare our model with a recent high-resolution observation of a young stellar object Elias 2–27, whose circumstellar disk has grand-design spiral arms. We find good agreement between our theoretical model and the observation. Our model suggests that the grand-design spiral arms around Elias 2–27 are consistent with material arms formed by gravitational instability. If such spiral arms commonly exist in young circumstellar disks, it implies that young circumstellar disks are considerably massive and gravitational instability is the key processmore » of angular momentum transport.« less

Authors:
;  [1];  [2];  [3];  [4]
  1. Department of Earth and Space Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan)
  2. Department of Earth and Planetary Sciences, Faculty of Sciences, Kyushu University, Nishi-ku, Fukuoka 819-0395 (Japan)
  3. Department of Physics, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan)
  4. Department of Physics, The University of Tokyo, Tokyo 113-0033 (Japan)
Publication Date:
OSTI Identifier:
22654568
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 835; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ANGULAR MOMENTUM; ANGULAR MOMENTUM TRANSFER; CLOUDS; COMPARATIVE EVALUATIONS; GRAVITATIONAL INSTABILITY; MAGNETOHYDRODYNAMICS; RADIANT HEAT TRANSFER; RESOLUTION; ROTATION; SIMULATION; STARS

Citation Formats

Tomida, Kengo, Lin, Chia Hui, Machida, Masahiro N., Hosokawa, Takashi, and Sakurai, Yuya, E-mail: tomida@vega.ess.sci.osaka-u.ac.jp. Grand-design Spiral Arms in a Young Forming Circumstellar Disk. United States: N. p., 2017. Web. doi:10.3847/2041-8213/835/1/L11.
Tomida, Kengo, Lin, Chia Hui, Machida, Masahiro N., Hosokawa, Takashi, & Sakurai, Yuya, E-mail: tomida@vega.ess.sci.osaka-u.ac.jp. Grand-design Spiral Arms in a Young Forming Circumstellar Disk. United States. doi:10.3847/2041-8213/835/1/L11.
Tomida, Kengo, Lin, Chia Hui, Machida, Masahiro N., Hosokawa, Takashi, and Sakurai, Yuya, E-mail: tomida@vega.ess.sci.osaka-u.ac.jp. Fri . "Grand-design Spiral Arms in a Young Forming Circumstellar Disk". United States. doi:10.3847/2041-8213/835/1/L11.
@article{osti_22654568,
title = {Grand-design Spiral Arms in a Young Forming Circumstellar Disk},
author = {Tomida, Kengo and Lin, Chia Hui and Machida, Masahiro N. and Hosokawa, Takashi and Sakurai, Yuya, E-mail: tomida@vega.ess.sci.osaka-u.ac.jp},
abstractNote = {We study formation and long-term evolution of a circumstellar disk in a collapsing molecular cloud core using a resistive magnetohydrodynamic simulation. While the formed circumstellar disk is initially small, it grows as accretion continues, and its radius becomes as large as 200 au toward the end of the Class-I phase. A pair of grand-design spiral arms form due to gravitational instability in the disk, and they transfer angular momentum in the highly resistive disk. Although the spiral arms disappear in a few rotations as expected in a classical theory, new spiral arms form recurrently as the disk, soon becoming unstable again by gas accretion. Such recurrent spiral arms persist throughout the Class-0 and I phases. We then perform synthetic observations and compare our model with a recent high-resolution observation of a young stellar object Elias 2–27, whose circumstellar disk has grand-design spiral arms. We find good agreement between our theoretical model and the observation. Our model suggests that the grand-design spiral arms around Elias 2–27 are consistent with material arms formed by gravitational instability. If such spiral arms commonly exist in young circumstellar disks, it implies that young circumstellar disks are considerably massive and gravitational instability is the key process of angular momentum transport.},
doi = {10.3847/2041-8213/835/1/L11},
journal = {Astrophysical Journal Letters},
number = 1,
volume = 835,
place = {United States},
year = {Fri Jan 20 00:00:00 EST 2017},
month = {Fri Jan 20 00:00:00 EST 2017}
}
  • We report the ALMA Cycle 2 observations of the Class I binary protostellar system L1551 NE in the 0.9 mm continuum, C{sup 18}O (3–2), {sup 13}CO (3–2), SO (7{sub 8}–6{sub 7}), and CS (7–6) emission. At 0.″18 (=25 au) resolution, ∼4 times higher than that of our Cycle 0 observations, the circumbinary disk (CBD) as seen in the 0.9 mm emission is shown to be composed of a northern and a southern spiral arm, with the southern arm connecting to the circumstellar disk (CSD) around Source B. The western parts of the spiral arms are brighter than the eastern parts,more » suggesting the presence of an m = 1 spiral mode. In the C{sup 18}O emission, the infall gas motions in the interarm regions and the outward gas motions in the arms are identified. These observed features are well reproduced with our numerical simulations, where gravitational torques from the binary system impart angular momenta to the spiral-arm regions and extract angular momenta from the interarm regions. Chemical differentiation of the CBD is seen in the four molecular species. Our Cycle 2 observations have also resolved the CSDs around the individual protostars, and the beam-deconvolved sizes are 0.″29 × 0.″19 (=40 × 26 au) (P.A. = 144°) and 0.″26 × 0.″20 (=36 × 27 au) (P.A. = 147°) for Sources A and B, respectively. The position and inclination angles of these CSDs are misaligned with those of the CBD. The C{sup 18}O emission traces the Keplerian rotation of the misaligned disk around Source A.« less
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