The ALMA-PILS survey: the first detection of doubly deuterated methyl formate (CHD<sub>2</sub>OCHO) in the ISM

Manigand, S.; Calcutt, H.; Jørgensen, J. K.; Taquet, V.; Müller, H. S. P.; Coutens, A.; Wampfler, S. F.; Ligterink, N. F. W.; Drozdovskaya, M. N.; Kristensen, L. E.; Wiel, M. H. D. van der; Bourke, Tyler L.

doi:10.1051/0004-6361/201832844

Cited by 54 publications

(81 citation statements)

References 55 publications

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“…This is slightly different from the 65 • ±10 • derived by Oya et al (2016), but radial profiles along a position angle of 45 • or 65 • are very similar. For all lines, the emission peaks on either side of the continuum peak, as has been seen for most other species toward IRAS 16293A (see e.g., Calcutt et al 2018;Manigand et al 2019). This could correspond to the double peaks seen in cm continuum emission (Wootten 1989;Chandler et al 2005;Pech et al 2010), although those positions are slightly off (see discussion in Calcutt et al 2018).…”

Section: Peak Fluxessupporting

confidence: 62%

Temperature profiles of young disk-like structures

Hoff

Dishoeck

Jørgensen

et al. 2019

A&A

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Context. Temperature is a crucial parameter in circumstellar disk evolution and planet formation, because it governs the resistance of the gas to gravitational instability and sets the chemical composition of the planet-forming material. Aims. We set out to determine the gas temperature of the young disk-like structure around the Class 0 protostar IRAS 16293-2422A. Methods. We use Atacama Large Millimeter/submillimeter Array (ALMA) observations of multiple H 2 CS J = 7 − 6 and J = 10 − 9 lines from the Protostellar Interferometric Line Survey (PILS) to create a temperature map for the inner ∼200 AU of the disk-like structure. This molecule is a particularly useful temperature probe because transitions between energy levels with different K a quantum numbers operate only through collisions.Results. Based on the H 2 CS line ratios, the temperature is between ∼100-175 K in the inner ∼150 AU, and drops to ∼75 K at ∼200 AU. At the current resolution (0.5 ∼70 AU), no jump is seen in the temperature at the disk-envelope interface. Conclusions. The temperature structure derived from H 2 CS is consistent with envelope temperature profiles that constrain the temperature from 1000 AU scales down to ∼100 AU, but does not follow the temperature rise seen in these profiles at smaller radii. Higher angular resolution observations of optically thin temperature tracers are needed to establish whether cooling by gas-phase water, the presence of a putative disk or the dust optical depth influences the gas temperature at 100 AU scales. The temperature at 100 AU is higher in IRAS 16293A than in the embedded Class 0/I disk L1527, consistent with the higher luminosity of the former.

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Section: Peak Fluxessupporting

confidence: 62%

Temperature profiles of young disk-like structures

Hoff

Dishoeck

Jørgensen

et al. 2019

A&A

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“…This is a deeply embedded protostellar system in L1689N containing two main complexes, IRAS 16239A to the south and IRAS 16293B to the north, separated by roughly 5 (e.g., Chen et al 2013;Jørgensen et al 2016). Both sources have been the target of extensive study for their hot core chemistry (e.g., Schöier et al 2002;Jørgensen et al 2011;Pineda et al 2012), including a dedicated ALMA survey to sample this molecular line emission of this source over 40 GHz in Band 7 (e.g., Jørgensen et al 2016;Manigand et al 2019, and references therein). The ALMA observations have also revealed an extensive dust Bridge between the stars (e.g., Pineda et al 2012;Jacobsen et al 2018;van der Wiel et al 2019).…”

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confidence: 99%

Dust Polarization toward Embedded Protostars in Ophiuchus with ALMA. III. Survey Overview

Sadavoy

Stephens

Myers

et al. 2019

ApJS

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We present 0.25 resolution (35 au) ALMA 1.3 mm dust polarization observations for 37 young stellar objects (YSOs) in the Ophiuchus molecular cloud. These data encompass all the embedded protostars in the cloud and several Flat and Class II objects to produce the largest, homogeneous study of dust polarization on disk scales to date. The goal of this study is to study dust polarization morphologies down to disk scales. We find that 14/37 (38%) of the observed YSOs are detected in polarization at our sensitivity. Nine of these sources have uniform polarization angles and four sources have azimuthal polarization structure. We find that the sources with uniform polarization tend to have steeper inclinations (> 60 • ) than those with azimuthal polarization (< 60 • ). Overall, the majority (9/14) of the detected sources have polarization morphologies and disk properties consistent with dust self-scattering processes in optically thick disks. The remaining sources may be instead tracing magnetic fields. Their inferred field directions from rotating the polarization vectors by 90 • are mainly poloidal or hourglass shaped. We find no evidence of a strong toroidal field component toward any of our disks. For the 23 YSOs that are undetected in polarization, roughly half of them have 3-sigma upper limits of < 2%. These sources also tend to have inclinations < 60 • and they are generally compact. Since lower inclination sources tend to have azimuthal polarization, these YSOs may be undetected in polarization due to unresolved polarization structure within our beam. We propose that disks with inclinations > 60 • are the best candidates for future polarization studies of dust selfscattering as these systems will generally show uniform polarization vectors that do not require very high resolution to resolve. We release the continuum and polarization images for all the sources with this publication. Data from the entire survey can be obtained from Dataverse. † Hubble Fellow

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“…Lower upper energy level lines are tracing a slightly more extended scale than the higher upper energy level lines. The scale that this emission is tracing is comparable to the scale traced by other complex organic molecules in both A and B, including methyl cyanide (CH 3 CN) and its isotopologues discussed in, and methyl formate (CH 3 OCHO,Manigand et al 2019). Recent analysis byAndron et al (2018), of CH 3 CCH towards this source using IRAM 30 m observations, claims CH 3 CCH emission on scales of 1700 au.…”

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confidence: 58%

“…Both these positions have been used previously to study the chemistry in both hot corinos (e.g. Ligterink et al 2017, Manigand et al 2019 to overcome issues of line blending and absorption contamination which affect the peak continuum position.…”

Section: Observational Results and Analysismentioning

confidence: 99%

“…The range in FWHMs and peak velocities modelled was based on previous analysis towards each of the offset 13.60 26.10 positions used in this work (e.g. Manigand et al 2019). This range covers several velocity channels either side of the previous best fit values to account for lines that might be broader or narrower than previously studied molecules, and molecules which may have a different peak velocity.…”

Section: Column Densities and Excitation Temperaturesmentioning

confidence: 99%

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The ALMA-PILS survey: propyne (CH₃CCH) in IRAS 16293–2422

Calcutt

Willis

Jørgensen

et al. 2019

A&A

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Context. Propyne (CH 3 CCH), also known as methyl acetylene, has been detected in a variety of environments, from Galactic starforming regions to extragalactic sources. Such molecules are excellent tracers of the physical conditions in star-forming regions, allowing the temperature and density conditions surrounding a forming star to be determined. Aims. This study explores the emission of CH 3 CCH in the low-mass protostellar binary, IRAS 16293-2422, examining the spatial scales traced by this molecule, as well as its formation and destruction pathways. Methods. Atacama Large Millimeter/submillimeter Array (ALMA) observations from the Protostellar Interferometric Line Survey (PILS) are used to determine the abundances and excitation temperatures of CH 3 CCH towards both protostars. This data allows us to explore spatial scales from 70 to 2400 au. This data is also compared with the three-phase chemical kinetics model MAGICKAL, to explore the chemical reactions of this molecule. Results. CH 3 CCH is detected towards both IRAS 16293A and IRAS 16293B, and is found to trace the hot corino component around each source in the PILS dataset. Eighteen transitions above 3σ are detected, enabling robust excitation temperatures and column densities to be determined in each source. In IRAS 16293A, an excitation temperature of 90 K and a column density of 7.8×10 15 cm −2 best fits the spectra. In IRAS 16293B, an excitation temperature of 100 K and 6.8×10 15 cm −2 best fits the spectra. The chemical modelling finds that in order to reproduce the observed abundances, both gas-phase and grain-surface reactions are needed. The gas-phase reactions are particularly sensitive to the temperature at which CH 4 desorbs from the grains. Conclusions. CH 3 CCH is a molecule whose brightness and abundance in many different regions can be utilised to provide a benchmark of molecular variation with the physical properties of star-forming regions. It is essential when making such comparisons, that the abundances are determined with a good understanding of the spatial scale of the emitting region, to ensure that accurate abundances are derived.

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The ALMA-PILS survey: the first detection of doubly deuterated methyl formate (CHD₂OCHO) in the ISM

Cited by 54 publications

References 55 publications

Temperature profiles of young disk-like structures

Temperature profiles of young disk-like structures

Dust Polarization toward Embedded Protostars in Ophiuchus with ALMA. III. Survey Overview

The ALMA-PILS survey: propyne (CH₃CCH) in IRAS 16293–2422

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The ALMA-PILS survey: the first detection of doubly deuterated methyl formate (CHD2OCHO) in the ISM

Cited by 54 publications

References 55 publications

Temperature profiles of young disk-like structures

Temperature profiles of young disk-like structures

Dust Polarization toward Embedded Protostars in Ophiuchus with ALMA. III. Survey Overview

The ALMA-PILS survey: propyne (CH3CCH) in IRAS 16293–2422

Contact Info

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The ALMA-PILS survey: the first detection of doubly deuterated methyl formate (CHD₂OCHO) in the ISM

The ALMA-PILS survey: propyne (CH₃CCH) in IRAS 16293–2422