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SPIRAL ARMS IN GRAVITATIONALLY UNSTABLE PROTOPLANETARY DISKS AS IMAGED IN SCATTERED LIGHT

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journal contribution
posted on 01.10.2019, 14:40 by Ruobing Dong (董若冰), Cassandra Hall, Ken Rice, Eugene Chiang (蒋诒曾)
Combining 3D smoothed-particle hydrodynamics and Monte Carlo radiative transfer calculations, we examine the morphology of spiral density waves induced by gravitational instability (GI) in protoplanetary disks, as they would appear in direct images at near-infrared (NIR) wavelengths. We find that systems with disk-to-star-mass ratios q = Mdisk/Må that are ∼0.25 or more may produce prominent spiral arms in NIR imaging, remarkably resembling features observed in the MWC 758 and SAO 206462 systems. The contrast of GI-induced arms at NIR wavelengths can reach a factor of ∼3, and their pitch angles are about 10°–15°. The dominant azimuthal wavenumber of GI-induced spiral arms roughly obeys m ∼ 1/q in the range 2 <~ 1/q <~ 8. In particular, a massive disk with q ≈ 0.5 can exhibit grand-design m = 2 spirals. GI-induced arms are in approximate corotation with the local disk, and may therefore trap dust particles by pressure drag. Although GI can produce NIR spiral arms with morphologies, contrasts, and pitch angles similar to those reported in recent observations, it also makes other demands that may or may not be satisfied in any given system. A GI origin requires that the spirals be relatively compact, on scales <~ 100 AU; that the disk be massive, q >~ 0.25; and that the accretion rate M.* be high, on the order of 10−6 Me yr−1 .

Funding

R.D. thanks Cathie Clarke and Roman Rafikov for educating him on the subject of GI. We thank Myriam Benisty and Antonio Garufi for kindly sharing with us the VLT/SPHERE image of MWC 758, and the VLT/NACO image of SAO 206462, respectively. We are grateful to the anonymous referee for constructive suggestions that improved the quality of the paper. This project is partially supported by NASA through Hubble Fellowship grant HST-HF-51320.01-A (R.D.) awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. E.C. acknowledges support from NASA and the NSF. Numerical calculations were performed on the SAVIO cluster provided by the Berkeley Research Computing program, supported by the UC Berkeley Vice Chancellor for Research and the Berkeley Center for Integrative Planetary Science.

History

Citation

The Astrophysical Journal, 2015, 812 (2), pp. L32-L32

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy

Version

VoR (Version of Record)

Published in

The Astrophysical Journal

Publisher

American Astronomical Society, IOP Publishing

eissn

2041-8213

Acceptance date

30/09/2015

Copyright date

2015

Available date

01/10/2019

Publisher version

https://iopscience.iop.org/article/10.1088/2041-8205/812/2/L32

Language

en