Transition from the infalling envelope to the Keplerian disk around L1551 IRS 5

Journal Article · Thu Nov 20 04:00:00 EST 2014 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/796/1/70· OSTI ID:22369990

Chou, Ti-Lin ^[1]; Takakuwa, Shigehisa; Yen, Hsi-Wei; Ohashi, Nagayoshi; Ho, Paul T. P., ^[2]

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1. Department of Physics, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 106, Taiwan (China)
2. Academia Sinica Institute of Astronomy and Astrophysics, P. O. Box 23-141, Taipei 10617, Taiwan (China)

We present combined Submillimeter Array (SMA) +Atacama Submillimeter Telescope Experiment (ASTE) images of the Class I protobinary L1551 IRS 5 in the CS (J = 7-6) line, the submillimeter images of L1551 IRS 5 with the most complete spatial sampling ever achieved (0.''9-36''). The SMA image of L1551 IRS 5 in the 343 GHz dust-continuum emission is also presented, which shows an elongated feature along the northwest to southeast direction (∼160 AU × 80 AU), perpendicular to the associated radio jets. The combined SMA+ASTE images show that the high-velocity (≳1.5 km s{sup –1}) CS emission traces the structure of the dust component and shows a velocity gradient along the major axis, which is reproduced by a geometrically thin Keplerian-disk model with a central stellar mass of ∼0.5 M {sub ☉}. The low-velocity (≲1.3 km s{sup –1}) CS emission shows an extended (∼1000 AU) feature that exhibits slight south (blueshifted) to north (redshifted) emission offsets, which is modeled with a rotating and infalling envelope with a conserved angular momentum. The rotational motion of the envelope connects smoothly to the inner Keplerian rotation at a radius of ∼64 AU. The infalling velocity of the envelope is ∼three times lower than the free-fall velocity toward the central stellar mass of 0.5 M {sub ☉}. These results demonstrate transition from the infalling envelope to the Keplerian disk, consistent with the latest theoretical studies of disk formation. We suggest that sizable (r ∼ 50-200 AU) Keplerian disks are already formed when the protostars are still deeply embedded in the envelopes.

• OSTI ID: 22369990
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 796; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ANGULAR MOMENTUM
BINARY STARS
DUSTS
EMISSION
IMAGES
MASS
MOLECULES
PROTOSTARS
RED SHIFT
ROTATION
STARS
TELESCOPES
VELOCITY