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Abstract We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of the Class I source Oph IRS 63 in the context of the Early Planet Formation in Embedded Disks large program. Our ALMA observations of Oph IRS 63 show a myriad of protostellar features, such as a shell-like bipolar outflow (in12CO), an extended rotating envelope structure (in13CO), a streamer connecting the envelope to the disk (in C18O), and several small-scale spiral structures seen toward the edge of the dust continuum (in SO). By analyzing the velocity pattern of13CO and C18O, we measure a protostellar mass ofM⋆= 0.5 ± 0.2M⊙and confirm the presence of a disk rotating at almost Keplerian velocity that extends up to ∼260 au. These calculations also show that the gaseous disk is about four times larger than the dust disk, which could indicate dust evolution and radial drift. Furthermore, we model the C18O streamer and SO spiral structures as features originating from an infalling rotating structure that continuously feeds the young protostellar disk. We compute an envelope-to-disk mass infall rate of ∼10−6M⊙yr−1and compare it to the disk-to-star mass accretion rate of ∼10−8M⊙yr−1, from which we infer that the protostellar disk is in a mass buildup phase. At the current mass infall rate, we speculate that soon the disk will become too massive to be gravitationally stable.
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A probable Keplerian disk feeding an optically revealed massive young star
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 > 8 M⊙) 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.
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- PAR ID:
- 10498235
- Publisher / Repository:
- Nature
- Date Published:
- Journal Name:
- Nature
- Volume:
- 625
- Issue:
- 7993
- ISSN:
- 0028-0836
- Page Range / eLocation ID:
- 55 to 59
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1038/s41586-023-06790-2
