Which molecule traces what: chemical diagnostics of protostellar sources

Tychoniec, Łukasz; van Dishoeck, Ewine F.; Hoff, Merel L. R. van 't; van Gelder, Martijn L.; Tabone, Benoît; Chen, Yuan; Harsono, Daniel; Hull, Charles L. H.; Hogerheijde, Michiel R.; Murillo, Nadia M.; Tobin, John J.

doi:10.48550/arxiv.2107.03696

Cited by 3 publications

(4 citation statements)

References 142 publications

(196 reference statements)

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“…The detected molecules presented in Sect. Results substantially expand the number of identified species in Serpens SMM1 24,26,27 . Particularly noteworthy is the detection of CH 3 C(O)NH 2 , making SMM1-a the lowest luminosity and mass object where acetamide is securely identified, with only a tentative detection of the molecule in the low-mass protostar IRAS 16293-2422B 20 .…”

Section: Discussionmentioning

confidence: 62%

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The prebiotic molecular inventory of Serpens SMM1: II. The building blocks of peptide chains

Ligterink¹,

Ahmadi²,

Luitel³

et al. 2022

Preprint

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This work aims to constrain the abundances of interstellar amides, by searching for this group of prebiotic molecules in the intermediate-mass protostar Serpens SMM1-a. ALMA observations are conducted toward Serpens SMM1. A spectrum is extracted toward the SMM1-a position and analyzed with the CASSIS line analysis software for the presence of characteristic rotational lines of a number of amides and other molecules. NH 2 CHO, NH 2 CHO ν 12 =1, NH 13 2 CHO, CH 3 C(O)NH 2 ν=0,1, CH 2 DOH, CH 3 CHO, and CH 3 C(O)CH 3 are securely detected, while trans-NHDCHO, NH 2 CDO, CH 3 NHCHO ν=0,1, CH 3 COOH, and HOCH 2 CHO are tentatively identified. The results of this work are compared with detections presented in the literature. A uniform CH 3 C(O)NH 2 /NH 2 CHO ratio is found for a group of interstellar sources with vast physical differences. A similar ratio is seen for CH 3 NHCHO, based on a smaller data sample. The D/H ratio of NH 2 CHO is about 1-3% and is close to values found in the low-mass source IRAS 16293-2422B. The formation of CH 3 C(O)NH 2 and NH 2 CHO is likely linked. Formation of these molecules on grain surfaces during the dark cloud stage is a likely scenario. The high D/H ratio of NH 2 CHO is also seen as an indicationthat these molecules are formed on icy dust grains. As a direct consequence, amides are expected to be present in the most pristine material from which planetary systems form, thus providing a reservoir of prebiotic material.

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Section: Discussionmentioning

confidence: 62%

“…In this publication, observations of Serpens SMM1-a (hereafter SMM1-a), an intermediatemass Class 0 protostar in the Serpens cloud (D ≈ 436.0±10 pc 21 ), are used. In particular, the outflows of the SMM1 region are well studied 22,23 , but also its molecular inventory [24][25][26][27] .…”

Section: Introductionmentioning

confidence: 99%

The prebiotic molecular inventory of Serpens SMM1: II. The building blocks of peptide chains

Ligterink¹,

Ahmadi²,

Luitel³

et al. 2022

Preprint

Self Cite

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“…This could result in low CH 3 OH line intensities for some of our sources. X-ray destruction can be distinguished from the scenarios discussed here through observations of HCO + and its optically thin H 13 CO + isotopologue (see also van 't Hoff et al 2021): if X-ray destruction dominates, HCO + emission would be centrally peaked on source, having a high abundance even within the water snow line since its main destroyer (water) is absent. Notsu et al (2021), see their section 4.6, identify two sources in the Perseus Class 0 sample with weak CH 3 OH emission and centrally peaked HCO + for which this could be the case.…”

Section: Comparison With Observationsmentioning

confidence: 91%

Importance of source structure on complex organics emission II. Can disks explain lack of methanol emission from some low-mass protostars?

Nazari,

Tabone,

Rosotti

et al. 2022

Preprint

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Context. The protostellar stage is known to be the richest star formation phase in emission from gaseous complex organic molecules. However, some protostellar systems show little or no millimetre (mm) line emission of such species. This can be interpreted as a low abundance of complex organic molecules, alternatively complex species could be present in the system but are not seen in the gas. Aims. The goal is to investigate the latter hypothesis for methanol as the most abundant complex organic molecule in protostellar systems. This work aims to find out how effective dust optical depth is in hiding methanol in the gas and whether methanol can mainly reside in the ice due to the presence of a disk that lowers the temperatures. Hence, we will attempt to answer the question: Does the presence of a disk and optically thick dust reduce methanol emission even if methanol and other complex species are abundant in the ices and gas? Methods. Using the radiative transfer code RADMC-3D, methanol emission lines from an envelope-only model and an envelope-plusdisk model are calculated and compared with each other and the observations. Methanol gas and ice abundances are parameterised inside and outside of the snow surfaces based on values from observations. Both models include either dust grains with low mm opacity or high mm opacity and their physical parameters such as envelope mass and disk radius are varied. Results. Methanol emission from the envelope-only model is always stronger than from the envelope-plus-disk model by at least a factor ∼2 as long as the disk radius is larger than ∼30 au (for L = 8 L ). In most cases, this is due to lower temperatures (disk shadowing) and, hence, the smaller amount of warm ( 70 K) methanol inside the snow surface of the envelope-plus-disk model. The intensities drop by more than an order of magnitude for models including high mm opacity dust grains and disk radii of at least ∼50 au (for L = 8 L ) due to continuum over-subtraction. Conclusions. The line intensities from the envelope-only models match the observations moderately well when methanol emission is strong but overproduce the observations of protostars with lower methanol emission even with large dust optical depth effects. The envelope-plus-disk models can explain the bulk of the observations. However, they can only reproduce the observations of sources with high luminosities and very low methanol emission when dust optical depth is significant in the envelope and continuum oversubtraction becomes effective in the disk (high mm opacity dust grains are used). Therefore, both the effects of disk and dust optical depth should be considered to explain the observations. In conclusion, it is important to take physical structure into account in future chemical studies of low-mass protostars: Absence of gas-phase methanol emission does not imply absence of methanol molecules in either gas or ice.

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“…The recent development of observational capabilities (increased bandwidth of the Sub-millimeter Array (SMA), the upgrade of the NOEMA interferometer, and development of the ALMA observatory) have allowed us to observe a wide range of molecular lines as probes, not only to study the pristine chemistry in star-forming cores, but also to selectively study the physical processes at work in protostellar interiors, down to scales where disks form (Jørgensen et al 2020;Öberg and Bergin 2021). The warm inner envelope, apart from showing emission from complex organic molecules (COMs), also presents compact emission from small molecules like H 2 S, SO, OCS and H 13 CN, most likely related to ice sublimation and high-temperature chemistry (Tychoniec et al 2021).…”

Section: The Physical and Chemical Conditions In Inner Envelopes: Obs...mentioning

confidence: 99%

The role of magnetic fields in the formation of protostars, disks, and outflows

Tsukamoto¹,

Maury²,

Commerçon³

et al. 2022

Preprint

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We present our current understanding of the formation and early evolution of protostars, protoplanetary disks, and the driving of outflows as dictated by the interplay of magnetic fields and partially ionized gas in molecular cloud cores. In recent years, the field has witnessed enormous development through sub-millimeter observations which in turn have constrained models of protostar formation. As a result of these observations the state-of-the-art theoretical understanding of the formation and evolution of young stellar objects is described. In particular, we emphasize the importance of the coupling, decoupling, and re-coupling between weakly ionized gas and the magnetic field on appropriate scales. This highlights the complex and intimate relationship between gravitational collapse and magnetic fields in young protostars.

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Which molecule traces what: chemical diagnostics of protostellar sources

Cited by 3 publications

References 142 publications

The prebiotic molecular inventory of Serpens SMM1: II. The building blocks of peptide chains

The prebiotic molecular inventory of Serpens SMM1: II. The building blocks of peptide chains

Importance of source structure on complex organics emission II. Can disks explain lack of methanol emission from some low-mass protostars?

The role of magnetic fields in the formation of protostars, disks, and outflows

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