We present observations of the Class 0 protostar IRAS 16544–1604 in CB 68 from the “Early Planet Formation in Embedded Disks (eDisk)” ALMA Large program. The ALMA observations target continuum and lines at 1.3 mm with an angular resolution of ∼5 au. The continuum image reveals a dusty protostellar disk with a radius of ∼30 au seen close to edge-on and asymmetric structures along both the major and minor axes. While the asymmetry along the minor axis can be interpreted as the effect of the dust flaring, the asymmetry along the major axis comes from a real nonaxisymmetric structure. The C18O image cubes clearly show the gas in the disk that follows a Keplerian rotation pattern around a ∼0.14
- Award ID(s):
- 1715719
- PAR ID:
- 10312603
- Date Published:
- Journal Name:
- Astronomy & Astrophysics
- Volume:
- 650
- ISSN:
- 0004-6361
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
Abstract M ⊙central protostar. Furthermore, there are ∼1500 au scale streamer-like features of gas connecting from northeast, north–northwest, and northwest to the disk, as well as the bending outflow as seen in the12CO (2–1) emission. At the apparent landing point of the NE streamer, there is SO (65–54) and SiO (5–4) emission detected. The spatial and velocity structure of the NE streamer can be interpreted as a free-falling gas with a conserved specific angular momentum, and the detection of the SO and SiO emission at the tip of the streamer implies the presence of accretion shocks. Our eDisk observations have unveiled that the Class 0 protostar in CB 68 has a Keplerian-rotating disk with a flaring and nonaxisymmetric structure associated with accretion streamers and outflows. -
Abstract In this study, we reported the results of high-resolution (${0{^{\prime \prime}_{.}}14}$) Atacama Large Millimeter/submillimeter Array (ALMA) observations of the 225 GHz dust continuum and CO molecular emission lines from the transitional disk around SY Cha. Our high-resolution observations clearly revealed the inner cavity and the central point source for the first time. The radial profile of the ring can be approximated by a bright narrow ring superimposed on a fainter wide ring. Furthermore, we found that there is a weak azimuthal asymmetry in dust continuum emission. For gas emissions, we detected 12CO(2–1), 13CO(2–1), and C18O(2–1), from which we estimated the total gas mass of the disk to be 2.2 × 10−4 M ⊙ , assuming a CO/H2 ratio of 10−4. The observations showed that the gas is present inside the dust cavity. The analysis of the velocity structure of the 12CO(2–1) emission line revealed that the velocity is distorted at the location of the dust inner disk, which may be owing to a warping of the disk or radial gas flow within the cavity of the dust disk. High-resolution observations of SY Cha showed that this system is composed of a ring and a distorted inner disk, which may be common, as indicated by the survey of transitional disk systems at a resolution of ${\sim}{0{^{\prime \prime}_{.}}1}$.
-
Abstract Precise estimates of protostellar masses are crucial to characterize the formation of stars of low masses down to brown dwarfs (BDs;
M *< 0.08M ☉). The most accurate estimation of protostellar mass uses the Keplerian rotation in the circumstellar disk around the protostar. To apply the Keplerian rotation method to a protostar at the low-mass end, we have observed the Class 0 protostar IRAS 16253-2429 using the Atacama Large Millimeter/submillimeter Array (ALMA) in the 1.3 mm continuum at an angular resolution of 0.″07 (10 au), and in the12CO, C18O,13CO (J = 2–1), and SO (J N = 65−54) molecular lines, as part of the ALMA Large Program Early Planet Formation in Embedded Disks project. The continuum emission traces a nonaxisymmetric, disk-like structure perpendicular to the associated12CO outflow. The position–velocity (PV) diagrams in the C18O and13CO lines can be interpreted as infalling and rotating motions. In contrast, the PV diagram along the major axis of the disk-like structure in the12CO line allows us to identify Keplerian rotation. The central stellar mass and the disk radius are estimated to be ∼0.12–0.17M ☉and ∼13–19 au, respectively. The SO line suggests the existence of an accretion shock at a ring (r ∼ 28 au) surrounding the disk and a streamer from the eastern side of the envelope. IRAS 16253-2429 is not a proto-BD but has a central stellar mass close to the BD mass regime, and our results provide a typical picture of such very-low-mass protostars. -
Abstract Constraining the physical and chemical structure of young embedded disks is crucial for understanding the earliest stages of planet formation. As part of the Early Planet Formation in Embedded Disks Atacama Large Millimeter/submillimeter Array Large Program, we present high spatial resolution (∼0.″1 or ∼15 au) observations of the 1.3 mm continuum and 13 CO J = 2–1, C 18 O J = 2–1, and SO J N = 6 5 –5 4 molecular lines toward the disk around the Class I protostar L1489 IRS. The continuum emission shows a ring-like structure at 56 au from the central protostar and tenuous, optically thin emission extending beyond ∼300 au. The 13 CO emission traces the warm disk surface, while the C 18 O emission originates from near the disk midplane. The coincidence of the radial emission peak of C 18 O with the dust ring may indicate a gap-ring structure in the gaseous disk as well. The SO emission shows a highly complex distribution, including a compact, prominent component at ≲30 au, which is likely to originate from thermally sublimated SO molecules. The compact SO emission also shows a velocity gradient along a direction tilted slightly (∼15°) with respect to the major axis of the dust disk, which we interpret as an inner warped disk in addition to the warp around ∼200 au suggested by previous work. These warped structures may be formed by a planet or companion with an inclined orbit, or by a gradual change in the angular momentum axis during gas infall.more » « less
-
Abstract The canonical picture of star formation involves disk-mediated accretion, with Keplerian accretion disks and associated bipolar jets primarily observed in nearby, low-mass young stellar objects (YSOs). Recently, rotating gaseous structures and Keplerian disks have been detected around several massive (
M > 8M ⊙) YSOs (MYSOs)1–4, including several disk-jet systems5–7. All the known MYSO systems are in the Milky Way, and all are embedded in their natal material. Here we report the detection of a rotating gaseous structure around an extragalactic MYSO in the Large Magellanic Cloud. The gas motion indicates that there is a radial flow of material falling from larger scales onto a central disk-like structure. The latter exhibits signs of Keplerian rotation, so that there is a rotating toroid feeding an accretion disk and thus the growth of the central star. The system is in almost all aspects comparable to Milky Way high-mass YSOs accreting gas from a Keplerian disk. The key difference between this source and its Galactic counterparts is that it is optically revealed rather than being deeply embedded in its natal material as is expected of such a massive young star. We suggest that this is the consequence of the star having formed in a low-metallicity and low-dust content environment. Thus, these results provide important constraints for models of the formation and evolution of massive stars and their circumstellar disks.