A HOT AND MASSIVE ACCRETION DISK AROUND THE HIGH-MASS PROTOSTAR IRAS 20126+4104

Journal Article · Wed Jun 01 04:00:00 EDT 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/823/2/125· OSTI ID:22666235

Chen, Huei-Ru Vivien ^[1]; Keto, Eric; Zhang, Qizhou; Sridharan, T. K. ^[2]; Liu, Sheng-Yuan; Su, Yu-Nung ^[3]

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1. Institute of Astronomy and Department of Physics, National Tsing Hua University, 101, Sec. 2, Kuang Fu Road, Hsinchu 30013, Taiwan (China)
2. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02318 (United States)
3. Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei, 10617, Taiwan (China)

We present new spectral line observations of the CH{sub 3}CN molecule in the accretion disk around the massive protostar IRAS 20126+4104 with the Submillimeter Array, which, for the first time, measure the disk density, temperature, and rotational velocity with sufficient resolution (0.″37, equivalent to ∼600 au) to assess the gravitational stability of the disk through the Toomre- Q parameter. Our observations resolve the central 2000 au region that shows steeper velocity gradients with increasing upper state energy, indicating an increase in the rotational velocity of the hotter gas nearer the star. Such spin-up motions are characteristics of an accretion flow in a rotationally supported disk. We compare the observed data with synthetic image cubes produced by three-dimensional radiative transfer models describing a thin flared disk in Keplerian motion enveloped within the centrifugal radius of an angular-momentum-conserving accretion flow. Given a luminosity of 1.3 × 10{sup 4} L {sub ⊙}, the optimized model gives a disk mass of 1.5 M {sub ⊙} and a radius of 858 au rotating about a 12.0 M {sub ⊙} protostar with a disk mass accretion rate of 3.9 × 10{sup −5} M {sub ⊙} yr{sup −1}. Our study finds that, in contrast to some theoretical expectations, the disk is hot and stable to fragmentation with Q > 2.8 at all radii which permits a smooth accretion flow. These results put forward the first constraints on gravitational instabilities in massive protostellar disks, which are closely connected to the formation of companion stars and planetary systems by fragmentation.

• OSTI ID: 22666235
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 823; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ACCRETION DISKS
ACETONITRILE
COMPARATIVE EVALUATIONS
DENSITY
FRAGMENTATION
GRAVITATIONAL INSTABILITY
INTERSTELLAR SPACE
LUMINOSITY
MASS
MOLECULES
ORGANIC COMPOUNDS
PROTOSTARS
RADIANT HEAT TRANSFER
RESOLUTION
SPECTRA
STABILITY
STARS
THREE-DIMENSIONAL CALCULATIONS
VELOCITY