ALMA observations of infalling flows toward the Keplerian disk around the class I protostar L1489 IRS
- Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan (China)
- Department of Earth and Planetary Sciences, Kobe University, Kobe 657-8501 (Japan)
- Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)
- Subaru Telescope, National Astronomical Observatory of Japan, 650 North A'ohoku Place, Hilo, HI 96720 (United States)
- Department of Earth and Planetary Sciences, Faculty of Sciences, Kyushu University, Fukuoka 812-8581 (Japan)
- Chile Observatory, National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588 (Japan)
- Joint ALMA Observatory, Ave. Alonso de Cordova 3107, Vitacura, Santiago (Chile)
- Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)
- Department of Astronomical Science, The Graduate University for Advanced Studies (SOKENDAI), Osawa, Mitaka, Tokyo 181-8588 (Japan)
We have conducted ALMA observations in the 1.3 mm continuum and {sup 12}CO (2-1), C{sup 18}O (2-1), and SO (5{sub 6}-4{sub 5}) lines toward L1489 IRS, a Class I protostar surrounded by a Keplerian disk and an infalling envelope. The Keplerian disk is clearly identified in the {sup 12}CO and C{sup 18}O emission, and its outer radius (∼700 AU) and mass (∼0.005 M {sub ☉}) are comparable to those of disks around T Tauri stars. The protostellar mass is estimated to be 1.6 M {sub ☉} with the inclination angle of 66°. In addition to the Keplerian disk, there are blueshifted and redshifted off-axis protrusions seen in the C{sup 18}O emission pointing toward the north and the south, respectively, adjunct to the middle part of the Keplerian disk. The shape and kinematics of these protrusions can be interpreted as streams of infalling flows with a conserved angular momentum following parabolic trajectories toward the Keplerian disk, and the mass infalling rate is estimated to be ∼5 × 10{sup –7} M {sub ☉} yr{sup –1}. The specific angular momentum of the infalling flows (∼2.5 × 10{sup –3} km s{sup –1} pc) is comparable to that at the outer radius of the Keplerian disk (∼4.8 × 10{sup –3} km s{sup –1} pc). The SO emission is elongated along the disk major axis and exhibits a linear velocity gradient along the axis, which is interpreted to mean that the SO emission primarily traces a ring region in the flared Keplerian disk at radii of ∼250-390 AU. The local enhancement of the SO abundance in the ring region can be due to the accretion shocks at the centrifugal radius where the infalling flows fall onto the disk. Our ALMA observations unveiled both the Keplerian disk and the infalling gas onto the disk, and the disk can further grow by accreting material and angular momenta from the infalling gas.
- OSTI ID:
- 22365063
- Journal Information:
- Astrophysical Journal, Vol. 793, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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