Revealing the chemical structure of the Class I disc Oph-IRS 67

Villarmois, E. Artur de la; Kristensen, L. E.; Jørgensen, J. K.

doi:10.1051/0004-6361/201935575

Cited by 9 publications

(7 citation statements)

References 66 publications

(84 reference statements)

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“…The morphologies in Ser-emb 1, 8, and 15 are suggestive of either an outflow cavity or a proto-disk atmosphere, consistent with observations of small hydrocarbons towards other embedded sources (e.g. Oya et al 2014;Artur de la Villarmois et al 2019). In both cases we expect low shielding from radiation in these regions, supporting that C 2 H formation is favored by an intense irradiation field (Bergin et al 2016;Aikawa & Herbst 1999).…”

Section: H Hcn and C 18 O Chemistriessupporting

confidence: 84%

An evolutionary study of volatile chemistry in protoplanetary disks

Bergner,

Oberg,

Bergin

et al. 2020

Preprint

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The volatile composition of a planet is determined by the inventory of gas and ice in the parent disk. The volatile chemistry in the disk is expected to evolve over time, though this evolution is poorly constrained observationally. We present ALMA observations of C 18 O, C 2 H, and the isotopologues H 13 CN, HC 15 N, and DCN towards five Class 0/I disk candidates. Combined with a sample of fourteen Class II disks presented in Bergner et al. (2019b), this data set offers a view of volatile chemical evolution over the disk lifetime. Our estimates of C 18 O abundances are consistent with a rapid depletion of CO in the first ∼0.5-1 Myr of the disk lifetime. We do not see evidence that C 2 H and HCN formation are enhanced by CO depletion, possibly because the gas is already quite under-abundant in CO. Further CO depletion may actually hinder their production by limiting the gas-phase carbon supply. The embedded sources show several chemical differences compared to the Class II stage, which seem to arise from shielding of radiation by the envelope (impacting C 2 H formation and HC 15 N fractionation) and sublimation of ices from infalling material (impacting HCN and C 18 O abundances). Such chemical differences between Class 0/I and Class II sources may affect the volatile composition of planet-forming material at different stages in the disk lifetime.

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Section: H Hcn and C 18 O Chemistriessupporting

confidence: 84%

An evolutionary study of volatile chemistry in protoplanetary disks

Bergner,

Oberg,

Bergin

et al. 2020

Preprint

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“…From interferometric observations, CN emission has been used to study protoplaneatry discs (Artur de la Villarmois et al 2019;van Terwisga et al 2019;Öberg et al 2011) and some hot molecular cores (Qiu et al 2012;Zapata et al 2008). Beuther et al (2004), based on the investigation of two massive starforming regions, pointed out that CN does not trace the central molecular condensations but mainly gas in their near vicinity.…”

Section: Introductionmentioning

confidence: 99%

Cyano radical emission at small spatial scales towards massive protostars

Paron

Ortega

Marinelli

et al. 2021

A&A

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Context. The cyano radical (CN), one of the first detected interstellar molecular species, is a key molecule in many astrochemical chains. In particular, it is detected towards molecular cores, the birth places of stars, and it is involved in the rich chemistry that takes place at these sites. Aims. At present, there are not many studies on the emission of this molecular species at small spatial scales towards massive young stellar objects. We therefore present a high-angular resolution CN study towards a sample of massive protostars, with the aim of unveiling the spatial distribution at the small scale of the emission of this radical in relation to star-forming processes. Methods. The interstellar CN has a strong emission line at the rest frequency 226 874.764 MHz, thus we searched for observing projects in the Atacama Large Millimeter Array (ALMA) database regarding high-mass star-forming regions observed at Band 6. The used data set was observed in ALMA Cycle 3 with angular and spectral resolutions of 0.′′7 and 1.13 MHz, respectively. A sample of ten high-mass star-forming regions located in the first Galactic quadrant were selected on the basis that they present a clear emission of CN at the mentioned frequency. Results. We found that the CN traces both molecular condensations and the diffuse and extended gas surrounding them. In general, the molecular condensations traced by the maximums of the CN emission do not spatially coincide with the peaks of the continuum emission at 1.3 mm, which trace the molecular cores where massive stars are born. Based on the presence or lack of near-IR emission associated with such cores, we suggest that our sample is composed of sources at different stages of evolution. The CN is present in all sources, suggesting that this radical may be ubiquitous along the different star formation stages, and hence it may be involved in different chemical reactions occurring during the period of star formation. Additionally, other molecules such as CH3OCHO and CH2CHCN were detected towards the continuum peaks of some of the analysed cores. We found that the missing flux coming from extended spatial scales that are filtered out by the interferometer is an important issue to take into account in the analysis of some spectral features and the spatial distribution of the emission.

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“…In this regard, chemical studies with single-dish telescopes have been instrumental in determining the bulk chemical structure of large-scale envelopes around low-mass stars (>1000 au, e.g., Blake et al 1995;van Dishoeck & Blake 1998;Jørgensen et al 2004;Graninger et al 2016) down to the scales of a few hundred au with millimeter interferometers such as the Submillimeter Array and IRAM NOrthern Extended Millimeter Array (e.g., Jørgensen et al 2005Jørgensen et al , 2007Bisschop et al 2008;Maury et al 2014;Taquet et al 2015). With the Atacama Large Millimeter/submillimeter Array, it is now possible to spatially and spectrally resolve the molecular emission to isolate the Keplerian disk from the surrounding envelope (e.g., Sakai et al 2014a; Artur de la Villarmois et al 2018Villarmois et al , 2019b. This aspect makes it possible to explore the chemical structure of young disks and examine the early stages of planet formation.…”

Section: Introductionmentioning

confidence: 99%

Resolved molecular line observations reveal an inherited molecular layer in the young disk around TMC1A

Harsono

Wiel

Bjerkeli

et al. 2021

A&A

Self Cite

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Context. Physical processes that govern the star and planet formation sequence influence the chemical composition and evolution of protoplanetary disks. Recent studies allude to an early start to planet formation already during the formation of a disk. To understand the chemical composition of protoplanets, we need to constrain the composition and structure of the disks from whence they are formed. Aims. We aim to determine the molecular abundance structure of the young disk around the TMC1A protostar on au scales in order to understand its chemical structure and any possible implications for disk formation. Methods. We present spatially resolved Atacama Large Millimeter/submillimeter Array observations of CO, HCO+, HCN, DCN, and SO line emission, as well as dust continuum emission, in the vicinity of TMC1A. Molecular column densities are estimated both under the assumption of optically thin emission from molecules in local thermodynamical equilibrium (LTE) as well as through more detailed non-LTE radiative transfer calculations. Results. Resolved dust continuum emission from the disk is detected between 220 and 260 GHz. Rotational transitions from HCO+, HCN, and SO are also detected from the inner 100 au region. We further report on upper limits to vibrational HCN υ2 = 1, DCN, and N2D+ lines. The HCO+ emission appears to trace both the Keplerian disk and the surrounding infalling rotating envelope. HCN emission peaks toward the outflow cavity region connected with the CO disk wind and toward the red-shifted part of the Keplerian disk. From the derived HCO+ abundance, we estimate the ionization fraction of the disk surface, and find values that imply that the accretion process is not driven by the magneto-rotational instability. The molecular abundances averaged over the TMC1A disk are similar to its protostellar envelope and other, older Class II disks. We meanwhile find a discrepancy between the young disk’s molecular abundances relative to Solar System objects. Conclusions. Abundance comparisons between the disk and its surrounding envelope for several molecular species reveal that the bulk of planet-forming material enters the disk unaltered. Differences in HCN and H2O molecular abundances between the disk around TMC1A, Class II disks, and Solar System objects trace the chemical evolution during disk and planet formation.

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Revealing the chemical structure of the Class I disc Oph-IRS 67

Cited by 9 publications

References 66 publications

An evolutionary study of volatile chemistry in protoplanetary disks

An evolutionary study of volatile chemistry in protoplanetary disks

Cyano radical emission at small spatial scales towards massive protostars

Resolved molecular line observations reveal an inherited molecular layer in the young disk around TMC1A

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