Signs of Early-Stage Disk Growth Revealed With Alma

Yen, Hsi-Wei; Koch, Patrick M.; Takakuwa, Shigehisa; Krasnopolsky, Ruben; Ohashi, Nagayoshi; Aso, Yusuke

doi:10.3847/1538-4357/834/2/178

Cited by 138 publications

(236 citation statements)

References 98 publications

(178 reference statements)

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“…Another possible case is that a significant fraction of total angular momentum could be removed outside of 100 au. Although the centrifugal barrier is relatively small, the specific angular momentum expected in the former case is slightly larger than that of several lowmass disks and/or envelopes at the 100 au scale (e.g., Yen et al 2017), due to the larger stellar mass.…”

Section: Physical Interpretationmentioning

confidence: 99%

A Face-on Accretion System in High-mass Star Formation: Possible Dusty Infall Streams within 100 AU

Motogi

Hirota

Saito

et al. 2017

ApJ

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We report on interferometric observations of a face-on accretion system around the High-Mass young stellar object, G353.273+0.641. The innermost accretion system of 100 au radius was resolved in a 45 GHz continuum image taken with the Jansky-Very Large Array. Our spectral energy distribution analysis indicated that the continuum could be explained by optically thick dust emission. The total mass of the dusty system is ∼ 0.2 M ⊙ at minimum and up to a few M ⊙ depending on the dust parameters. 6.7 GHz CH 3 OH masers associated with the same system were also observed with the Australia Telescope Compact Array. The masers showed a spiral-like, non-axisymmetric distribution with a systematic velocity gradient. The line-of-sight velocity field is explained by an infall motion along a parabolic streamline that falls onto the equatorial plane of the face-on system. The streamline is quasi-radial and reaches the equatorial plane at a radius of 16 au. This is clearly smaller than that of typical accretion disks in High-Mass star formation, indicating that the initial angular momentum was very small, or the CH 3 OH masers selectively trace accreting material that has small angular momentum. In the former case, the initial specific angular momentum is estimated to be 8 × 10 20 (M * /10 M ⊙ ) 0.5 cm 2 s −1 , or a significant fraction of the initial angular momentum was removed outside of 100 au. The physical origin of such a streamline is still an open question and will be constrained by the higher-resolution (∼ 10 mas) thermal continuum and line observations with ALMA long baselines.

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Section: Physical Interpretationmentioning

confidence: 99%

A Face-on Accretion System in High-mass Star Formation: Possible Dusty Infall Streams within 100 AU

Motogi

Hirota

Saito

et al. 2017

ApJ

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“…The detailed disk properties is a subject of the future high-angular resolution observations. −3 -10 −1 M ⊙ (e.g., Tobin et al 2012;Ohashi et al 2014;Aso et al 2017;Yen et al 2017), however, others have no Keplerian disks (e.g., Yen et al 2015). While MHD simulations of disk formation (e.g., Tomida et al 2017) tend to predict heavy disks, young circumstellar disks have various masses and sizes.…”

Section: Physical Quantities Of Disk Of Mms-1mentioning

confidence: 99%

“…The velocity/spatial distribution of Keplerian disks is powerful tool to measure the central protostellar mass. Recent interferometric observations, especially with ALMA, have revealed Keplerian disks around the Class 0 protostars (e.g., Tobin et al 2012;Ohashi et al 2014;Aso et al 2017;Yen et al 2017), although such disks are not expected to be observed when a protostar is at a very young stage (e.g., Yen et al 2015) or when disk formation is suppressed by magnetic braking (e.g., Allen et al 2003;Mellon & Li 2008;Yen et al 2015). Molecular line observations toward YSOs having Keplerian disks also show active outflows with a size scale of 1000 AU and/or inflow motions, indicating that significant accretion activities onto the protostars and/or disks are continuing.…”

Section: Introductionmentioning

confidence: 99%

A Detached Protostellar Disk around a ∼0.2 M_⊙ Protostar in a Possible Site of a Multiple Star Formation in a Dynamical Environment in Taurus

Tokuda¹,

Onishi²,

Saigo³

et al. 2017

ApJ

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We report ALMA observations in 0.87 mm continuum and 12 CO (J = 3-2) toward a very low-luminosity (<0.1 L ⊙ ) protostar, which is deeply embedded in one of the densest core MC27/L1521F, in Taurus with an indication of multiple star formation in a highly dynamical environment. The beam size corresponds to ∼20 AU, and we have clearly detected blueshifted/redshifted gas in 12 CO associated with the protostar. The spatial/velocity distributions of the gas show there is a rotating disk with a size scale of ∼10 AU, a disk mass of ∼10 −4 M ⊙ and a central stellar mass of ∼0.2 M ⊙ . The observed disk seems to be detached from the surrounding dense gas, although it is still embedded at the center of the core whose density is ∼10 6 cm −3 . The current low-outflow activity and the very low luminosity indicate that the mass accretion rate onto the protostar is extremely low in spite of a very early stage of star formation. We may be witnessing the final stage of the formation of ∼0.2 M ⊙ protostar. However, we cannot explain the observed low luminosity with the standard pre-main-sequence evolutionary track unless we assume cold accretion with an extremely small initial radius of the protostar (∼0.65 R ⊙ ). These facts may challenge our current understanding of the low mass star formation, in particular the mass accretion process onto the protostar and the circumstellar disk.

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“…Although protostellar disks have been detected in some Class 0 sources (Lee 2011;Tobin et al 2012;Ohashi et al 2014), the disks in VeLLOs are likely still forming if they are indeed extremely young Class 0 sources. For example, Yen et al (2015Yen et al ( , 2017 suggest that the disk size is very small (6 au) in one of our targets, DCE185 (IRAS 16253), while it shows clear evidence of a recent accretion burst. As a result, the high fraction of burst signatures in VeLLOs is in conflict with the simulation results (Vorobyov et al 2013;Vorobyov & Basu 2015), in which episodic accretion processes are found to occur preferentially during the Class I stage after the formation of a star-disk system.…”

Section: Timeline Of the Episodic Accretion Processmentioning

confidence: 99%

Probing Episodic Accretion in Very Low Luminosity Objects

Hsieh

Murillo

Беллоче

et al. 2018

ApJ

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Episodic accretion has been proposed as a solution to the long-standing luminosity problem in star formation; however, the process remains poorly understood. We present observations of line emission from N 2 H + and CO isotopologues using the Atacama Large Millimeter/submillimeter Array (ALMA) in the envelopes of eight very low luminosity objects (VeLLOs). In five of the sources the spatial distribution of emission from N 2 H + and CO isotopologues shows a clear anticorrelation. It is proposed that this is tracing the CO snow line in the envelopes: N 2 H + emission is depleted toward the center of these sources, in contrast to the CO isotopologue emission, which exhibits a peak. The positions of the CO snow lines traced by the N 2 H + emission are located at much larger radii than those calculated using the current luminosities of the central sources. This implies that these five sources have experienced a recent accretion burst because the CO snow line would have been pushed outward during the burst because of the increased luminosity of the central star. The N 2 H + and CO isotopologue emission from DCE161, one of the other three sources, is most likely tracing a transition disk at a later evolutionary stage. Excluding DCE161, five out of seven sources (i.e., ∼70%) show signatures of a recent accretion burst. This fraction is larger than that of the Class 0/I sources studied by Jørgensen et al. and Frimann et al., suggesting that the interval between accretion episodes in VeLLOs is shorter than that in Class 0/I sources.

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Signs of Early-Stage Disk Growth Revealed With Alma

Cited by 138 publications

References 98 publications

A Face-on Accretion System in High-mass Star Formation: Possible Dusty Infall Streams within 100 AU

A Face-on Accretion System in High-mass Star Formation: Possible Dusty Infall Streams within 100 AU

A Detached Protostellar Disk around a ∼0.2 M_⊙ Protostar in a Possible Site of a Multiple Star Formation in a Dynamical Environment in Taurus

Probing Episodic Accretion in Very Low Luminosity Objects

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Signs of Early-Stage Disk Growth Revealed With Alma

Cited by 138 publications

References 98 publications

A Face-on Accretion System in High-mass Star Formation: Possible Dusty Infall Streams within 100 AU

A Face-on Accretion System in High-mass Star Formation: Possible Dusty Infall Streams within 100 AU

A Detached Protostellar Disk around a ∼0.2 M⊙ Protostar in a Possible Site of a Multiple Star Formation in a Dynamical Environment in Taurus

Probing Episodic Accretion in Very Low Luminosity Objects

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Resources

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A Detached Protostellar Disk around a ∼0.2 M_⊙ Protostar in a Possible Site of a Multiple Star Formation in a Dynamical Environment in Taurus