Evidence for the start of planet formation in a young circumstellar disk

Harsono, Daniel; Bjerkeli, P.; Wiel, M. H. D. van der; Ramsey, Jon P.; Maud, L. T.; Kristensen, L. E.; Jørgensen, J. K.

doi:10.1038/s41550-018-0497-x

Cited by 117 publications

(143 citation statements)

References 82 publications

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“…This suggests that the suppression of gas emission in the inner disk region is due to the presence of optically thick, saturated continuum emission that overwhelms any line emission even if it lies closer to the observer. A similar morphology was discussed for a younger object by Harsono et al (2018), who invoked the substantial presence of grains larger than 1 mm to explain the high optical depth. A direct consequence of this effect is that the gaseous distribution in the inner 50 au around DG Tau B cannot be constrained from millimeter observations, but will instead require centimeter maps.…”

Section: Origin Of the Inner Depressionsupporting

confidence: 66%

ALMA chemical survey of disk-outflow sources in Taurus (ALMA-DOT)

Garufi

Podio

Codella

et al. 2020

A&A

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The chemical composition of planets is determined by the distribution of the various molecular species in the protoplanetary disk at the time of their formation. To date, only a handful of disks have been imaged in multiple spectral lines with high spatial resolution. As part of a small campaign devoted to the chemical characterization of disk-outflow sources in Taurus, we report on new ALMA Band 6 (∼1.3 mm) observations with ∼0.15 (20 au) resolution toward the embedded young star DG Tau B. Images of the continuum emission reveals a dust disk with rings and, putatively, a leading spiral arm. The disk, as well as the prominent outflow cavities, are detected in CO, H 2 CO, CS, and CN; instead, they remain undetected in SO 2 , HDO, and CH 3 OH. From the absorption of the back-side outflow, we inferred that the disk emission is optically thick in the inner 50 au. This morphology explains why no line emission is detected from this inner region and poses some limitations toward the calculation of the dust mass and the characterization of the inner gaseous disk. The H 2 CO and CS emission from the inner 200 au is mostly from the disk, and their morphology is very similar. The CN emission significantly differs from the other two molecules as it is observed only beyond 150 au. This ring-like morphology is consistent with previous observations and the predictions of thermochemical disk models. Finally, we constrained the disk-integrated column density of all molecules. In particular, we found that the CH 3 OH/H 2 CO ratio must be smaller than ∼2, making the methanol non-detection still consistent with the only such ratio available from the literature (1.27 in TW Hya).

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Section: Origin Of the Inner Depressionsupporting

confidence: 66%

ALMA chemical survey of disk-outflow sources in Taurus (ALMA-DOT)

Garufi

Podio

Codella

et al. 2020

A&A

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“…This suggests that the maximum size of dust grains should be larger than centimeter sizes (e.g., Ricci et al 2010;Testi et al 2014). The large disk mass of about 0.1 M ⊙ and the large grain size imply a possibility of planet formation even in the early evolutionary stage, as argued by Harsono et al (2018). Figure 14 shows the spectral maps of H 13 CO + and C 17 O on top of the image of the CH 3 OH integrated intensity map.…”

Section: Dust Grain Growthmentioning

confidence: 84%

The Circumstellar Environment around the Embedded Protostar EC 53

Lee

Aikawa

et al. 2020

ApJ

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EC53 is an embedded protostar with quasi-periodic emission in the near-IR and sub-mm. We use ALMA high-resolution observations of continuum and molecular line emission to describe the circumstellar environment of EC 53. The continuum image reveals a disk with a flux that suggests a mass of 0.075 M ⊙ , much less than the estimated mass in the envelope, and an in-band spectral index that indicates grain growth to centimeter sizes. Molecular lines trace the outflow cavity walls, infalling and rotating envelope, and/or the Keplerian disk. The rotation profile of the C 17 O 3-2 line emission cannot isolate the Keplerian motion clearly although the lower limit of the protostellar mass can be calculated as 0.3 ± 0.1 M ⊙ if the Keplerian motion is adopted. The weak CH 3 OH emission, which is anti-correlated with the H 13 CO + 4-3 line emission, indicates that the water snow line is more extended than what expected from the current luminosity, attesting to bygone outburst events. The extended snow line may persist for longer at the disk surface because the lower density increases the freeze-out timescale of methanol and water.

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“…Our protostellar sample consist of three sources: the TMC1A, HL Tau, and DG Tau systems, all with known large Keplerian rotating disks (>100 au, Isella et al 2010;ALMA Partnership et al 2015;Aso et al 2015;Harsono et al 2018). We chose these large protostellar disks so that these disks and their inner envelopes can be spatially resolved with NOEMA C or D configurations.…”

Section: Observationsmentioning

confidence: 99%

Rapid Evolution of Volatile CO from the Protostellar Disk Stage to the Protoplanetary Disk Stage

Zhang

Schwarz

Bergin

2020

ApJL

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Recent observations show that the CO gas abundance, relative to H 2 , in many 1-10 Myr old protoplanetary disks may be heavily depleted, by a factor of 10-100 compared to the canonical interstellar medium value of 10 −4 . When and how this depletion happens can significantly affect compositions of planetesimals and atmospheres of giant planets. It is therefore important to constrain if the depletion occurs already at the earliest protostellar disk stage. Here we present spatially resolved observations of C 18 O, C 17 O, and 13 C 18 O J=2-1 lines in three protostellar disks. We show that the C 18 O line emits from both the disk and the inner envelope, while C 17 O and 13 C 18 O lines are consistent with a disk origin. The line ratios indicate that both C 18 O and C 17 O lines are optically thick in the disk region, and only 13 C 18 O line is optically thin. The line profiles of the 13 C 18 O emissions are best reproduced by Keplerian gaseous disks at similar sizes as their mm-continuum emissions, suggesting small radial separations between the gas and mm-sized grains in these disks, in contrast to the large separation commonly seen in protoplanetary disks. Assuming a gas-to-dust ratio of 100, we find that the CO gas abundance in these protostellar disks are consistent with the ISM abundance within a factor of 2, nearly one order of magnitude higher than the average value of 1-10 Myr old disks. These results suggest that there is a fast, ∼1 Myr, evolution of the abundance of CO gas from the protostellar disk stage to the protoplanetary disk stage.

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Evidence for the start of planet formation in a young circumstellar disk

Cited by 117 publications

References 82 publications

ALMA chemical survey of disk-outflow sources in Taurus (ALMA-DOT)

ALMA chemical survey of disk-outflow sources in Taurus (ALMA-DOT)

The Circumstellar Environment around the Embedded Protostar EC 53

Rapid Evolution of Volatile CO from the Protostellar Disk Stage to the Protoplanetary Disk Stage

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