13C17O suggests gravitational instability in the HL Tau disc

Booth, Alice S.; Ilee, John D.

doi:10.1093/mnrasl/slaa014

Cited by 43 publications

(34 citation statements)

References 57 publications

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“…The systemic velocity is ∼ +7.0 km s −1 (in agreement with ALMA Partnership et al 2015;Wu et al 2018). The same rotating gradient has been observed using HCO + (ALMA Partnership et al 2015;Yen et al 2019), C 18 O (Wu et al 2018), and 13 C 17 O (Booth & Ilee 2020). Also the emission towards IRAS04302 disk shows a rotation pattern.…”

Section: H 2 Cs Kinematicssupporting

confidence: 84%

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

Codella

Podio

Garufi

et al. 2020

A&A

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Context. Planet formation starts around Sun-like protostars with ages ≤ 1 Myr: what is the chemical compositions in disks? Aims. To trace the radial and vertical spatial distribution of H 2 CS, a key species of the S-bearing chemistry, in protoplanetary disks. To analyse the observed distributions in light of the H 2 CS binding energy, in order to discuss the role of thermal desorption in enriching the gas disk component. Methods. In the context of the ALMA chemical survey of Disk-Outflow sources in the Taurus star forming region (ALMA-DOT), we observed five Class I or early Class II sources with the o-H 2 CS(7 1,6 − 6 1,5) line. ALMA-Band 6 was used, reaching spatial resolutions 40 au, i.e. Solar System spatial scales. We also estimated the binding energy of H 2 CS using quantum mechanical calculations, for the first time, for an extended, periodic, crystalline ice. Results. We imaged H 2 CS emission in two rotating molecular rings in the HL Tau and IRAS04302+2247 disks. The outer radii are ∼ 140 au (HL Tau), and 115 au (IRAS 04302+2247). The edge-on geometry of IRAS 04302+2247 allows us to reveal that H 2 CS emission peaks, at radii of 60-115 au, at z = ± 50 au from the equatorial plane. Assuming LTE conditions, the column densities are ∼ 10 14 cm −2. Upper limits of a few 10 13 cm −2 have been estimated for the H 2 CS column densities in DG Tau, DG Tau B, and Haro 6-13 disks. For HL Tau, we derive, for the first time, the [H 2 CS]/[H] abundance in a protoplanetary disk (10 −14). The binding energy of H 2 CS computed for extended crystalline ice and amorphous ices is 4258 K and 3000-4600 K, respectively, implying a thermal evaporation where dust temperature is ≥ 50-80 K. Conclusions. H 2 CS traces the so-called warm molecular layer, a region previously sampled using CS, and H 2 CO. Thioformaldehyde peaks closer to the protostar than H 2 CO and CS, plausibly due to the relatively high-excitation level of observed 7 1,6 − 6 1,5 line (60 K). The H 2 CS binding energy implies that thermal desorption dominates in thin, au-sized, inner and/or upper disk layers, indicating that the observed H 2 CS emitting up to radii larger than 100 au is likely injected in the gas due to non-thermal processes.

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Section: H 2 Cs Kinematicssupporting

confidence: 84%

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

Codella

Podio

Garufi

et al. 2020

A&A

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“…Molecules on the icy mantles are then released due to either thermal desorption in the inner and upper disk or non-thermal processes (UV, X-ray, cosmic-ray induced, or reactive desorption). Reasonably, the bulk of the emission observed in our maps lies outside of the CO snowline at the midplane (assumed at 30 and 50 au in DG Tau and HL Tau, Podio et al 2019;Booth & Ilee 2020). Therefore, non-thermal desorption of molecules from icy grains is certainly possible, as also suggested by Podio et al (2020a), who showed that the H 2 CO flux around IRAS 04302 is maximized in the warm molecular layer and is only moderately dimmed (by a factor of 2) toward the midplane.…”

Section: Cn Cs and H 2 Co Distribution Across The Diskmentioning

confidence: 80%

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

Garufi

Podio

Codella

et al. 2021

A&A

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We present an overview of the ALMA chemical survey of disk-outflow sources in Taurus (ALMA-DOT), a campaign devoted to the characterization of the molecular emission from partly embedded young stars. The project is aimed at attaining a better understanding of the gaseous products delivered to planets by means of high-resolution maps of the assorted lines probing disks at the time of planet formation (≲1 Myr). Nine different molecules are surveyed through our observations of six Class I/flat-spectrum sources. As part of a series of articles analyzing specific targets and molecules, in this work we describe the sample and provide a general overview of the results, focusing specifically on the spatial distribution, column densities, and abundance ratios of H2CO, CS, and CN. In these embedded sources, the 12CO emission is dominated by envelope and outflow emission while the CS and, especially, the H2CO are good tracers of the gaseous disk structure. The spatial distribution and brightness of the o-H2CO 31,2−21,1 and CS 5−4 lines are very similar to each other and across all targets. The CN 2−1 line emission is fainter and distributed over radii larger than the dust continuum. The H2CO and CS emission is always dimmed in the inner ~50 au. While the suppression by the dusty disk and absorption by the line-of-sight material significantly contributes to this inner depression, an actual decrease in the column density is plausible in most cases, making the observed ring-like morphology realistic. We also found that the gaseous disk extent, when traced by H2CO (150−390 au), is always 60% larger than the dust disk. This systematic discrepancy may, in principle, be explained by the different optical depth of continuum and line emission without invoking any dust radial drift. Finally, the o-H2CS 71,6−61,5 and CH3OH 50,5−40,4 line emission are detected in two disks and one disk, respectively, while the HDO is never detected. The H2CO column densities are 12−50 times larger than those inferred for Class II sources while they are in line with those of other Class 0/I. The CS column densities are lower than those of H2CO, which is an opposite trend with regard to Class II objects. We also inferred abundance ratios between the various molecular species finding, among others, a H2CS/H2CO ratio that is systematically lower than unity (0.4−0.7 in HL Tau, 0.1 − 0.2 in IRAS 04302+2247, and <0.4 in all other sources), as well as a CH3OH/H2CO ratio (<0.7 in HL Tau and 0.5−0.7 in IRAS 04302+2247) that is lower than the only available estimate in a protoplanetary disks (1.3 in TW Hya) and between one and two orders of magnitude lower than those of the hot corinos around Class 0 protostars. These results are a first step toward the characterization of the disk’s chemical evolution, which ought to be complemented by subsequent observations of less exceptional disks and customized thermo-chemical modeling.

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“…However, even C 18 O lines can be optically thick in protostellar disks (van 't Hoff et al 2018). A more robust way is to employ rarer CO isotopologue lines (e.g., C 17 O, 13 C 18 O, 13 C 17 O ) that have smaller optical depths (Zhang et al 2017;Artur de la Villarmois et al 2018;Booth et al 2019;Booth & Ilee 2020).…”

Section: Introductionmentioning

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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13C17O suggests gravitational instability in the HL Tau disc

Cited by 43 publications

References 57 publications

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

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

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

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

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