Deep, Broadband Spectral Line Surveys of Molecule-rich Interstellar Clouds

Weaver, Susanna L. Widicus; Laas, J.; Zou, Luyao; Kroll, Jay A.; Rad, Mary Lynn; Hays, Brian M.; Sanders, James; Lis, D. C.; Cross, Trevor; Wehres, Nadine; McGuire, Brett A.; Sumner, Matthew

doi:10.3847/1538-4365/aa8098

Cited by 29 publications

(9 citation statements)

References 268 publications

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“…L1544: Caselli et al (2002); Gupta et al (2009); Marcelino et al (2009, 2010); Vastel et al (2014, 2015, 2016, 2018a,b); Jiménez-Serra et al (2016); Quénard et al (2017); Cernicharo et al (2018). B1-b: Marcelino et al (2005, 2009, 2010); Agúndez et al (2008); Öberg et al (2010); Cernicharo et al (2012); Loison et al (2016, 2017); Fuente et al (2016); Widicus Weaver et al (2017); Marcelino et al (in preparation). L1527: Sakai et al (2008b); Marcelino et al (2009, 2010); Araki et al (2017); Yoshida et al (2019).…”

Section: Figmentioning

confidence: 99%

A sensitive λ 3 mm line survey of L483

Agúndez

Marcelino

Cernicharo

et al. 2019

A&A

103

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An exhaustive chemical characterization of dense cores is mandatory to our understanding of chemical composition changes from a starless to a protostellar stage. However, only a few sources have had their molecular composition characterized in detail. Here we present a λ 3 mm line survey of L483, a dense core around a Class 0 protostar, which was observed with the IRAM 30m telescope in the 80-116 GHz frequency range. We detected 71 molecules (140 including different isotopologs), most of which are present in the cold and quiescent ambient cloud according to their narrow lines (FWHM ~0.5 km s−1) and low rotational temperatures (≲10 K). Of particular interest among the detected molecules are the cis isomer of HCOOH, the complex organic molecules HCOOCH3, CH3OCH3, and C2H5OH, a wide variety of carbon chains, nitrogen oxides like N2O, and saturated molecules like CH3SH, in addition to eight new interstellar molecules (HCCO, HCS, HSC, NCCNH+, CNCN, NCO, H2NCO+, and NS+) whose detection has already been reported. In general, fractional molecular abundances in L483 are systematically lower than in TMC-1 (especially for carbon chains), tend to be higher than in L1544 and B1-b, and are similar to those in L1527. Apart from the overabundance of carbon chains in TMC-1, we find that L483 does not have a marked chemical differentiation with respect to starless/prestellar cores like TMC-1 and L1544, although it does chemically differentiate from Class 0 hot corino sources like IRAS 16293–2422. This fact suggests that the chemical composition of the ambient cloud of some Class 0 sources could be largely inherited from the dark cloud starless/prestellar phase. We explore the use of potential chemical evolutionary indicators, such as the HNCO/C3S, SO2/C2S, and CH3SH/C2S ratios, to trace the prestellar/protostellar transition. We also derived isotopic ratios for a variety of molecules, many of which show isotopic ratios close to the values for the local interstellar medium (remarkably all those involving 34S and 33S), while there are also several isotopic anomalies like an extreme depletion in 13C for one of the two isotopologs of c-C3H2, a drastic enrichment in 18O for SO and HNCO (SO being also largely enriched in 17O), and different abundances for the two 13C substituted species of C2H and the two 15N substituted species of N2H+. We report the first detection in space of some minor isotopologs like c-C3D. The exhaustive chemical characterization of L483 presented here, together with similar studies of other prestellar and protostellar sources, should allow us to identify the main factors that regulate the chemical composition of cores along the process of formation of low-mass protostars.

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Section: Figmentioning

confidence: 99%

A sensitive λ 3 mm line survey of L483

Agúndez

Marcelino

Cernicharo

et al. 2019

A&A

103

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“…However, also systematic surveys do not present a uniform picture (see the bottom panel of Figure 2 for results from the survey by Widicus Weaver et al 2017). The spread could illustrate that the soot line is not resolved in all sources, but sources with higher N-COM excitation temperatures span the entire luminosity and distance range among the high-mass sources in the sample.…”

Section: Discussion and Outlookmentioning

confidence: 98%

“…Highest excitation temperature among all nitrogen-bearing COMs versus that among all oxygen-bearing COMs reported in a study for a protostellar source. The top panel provides an overview of the literature, while the middle panel only shows results for Orion KL and the bottom panel only shows results from the survey by WidicusWeaver et al (2017). References are listed in Table1.…”

mentioning

confidence: 99%

Carbon-grain Sublimation: A New Top-down Component of Protostellar Chemistry

Hoff

Bergin

Jørgensen

et al. 2020

ApJL

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Earth's carbon deficit has been an persistent problem in our understanding of the formation of our solar system. A possible solution would be the sublimation of carbon grains at the so-called soot line (∼300 K) early in the planetformation process. Here, we argue that the most likely signatures of this process are an excess of hydrocarbons and nitriles inside the soot line, and a higher excitation temperature for these molecules compared to oxygen-bearing complex organics that desorb around the water snowline (∼100 K). Such characteristics have been reported in the literature, for example, in Orion KL, although not uniformly, potentially due to differences in the observational settings and analysis methods of different studies or the episodic nature of protostellar accretion. If this process is active, this would mean that there is a heretofore unknown component to the carbon chemistry during the protostellar phase that is acting from the top down-starting from the destruction of larger species-instead of from the bottom up from atoms. In the presence of such a top-down component, the origin of organic molecules needs to be re-explored.

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“… a And references therein. For more information on Galactic hot cores, see also, e.g., refs − and references therein. …”

Section: The Quest For Detecting Coms In the Magellanic Clouds With Almamentioning

confidence: 99%

Complex Organic Molecules in Star-Forming Regions of the Magellanic Clouds

Sewiło

Charnley

Schilke

et al. 2019

ACS Earth Space Chem.

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The Large and Small Magellanic Clouds (LMC and SMC), gas-rich dwarf companions of the Milky Way, are the nearest laboratories for detailed studies on the formation and survival of complex organic molecules (COMs) under metal poor conditions. To date, only methanol, methyl formate, and dimethyl ether have been detected in these galaxies -all three toward two hot cores in the N113 star-forming region in the LMC, the only extragalactic sources exhibiting complex hot core chemistry. We describe a small and diverse sample of the LMC and SMC sources associated with COMs or hot core chemistry, and compare the observations to theoretical model predictions. Theoretical models accounting for the physical conditions and metallicity of hot molecular cores in the Magellanic Clouds have been able to broadly account for the existing observations, but fail to reproduce the dimethyl ether abundance by more than an order of magnitude. We discuss future prospects for research in the field of complex chemistry in the low-metallicity environment. The detection of COMs in the Magellanic Clouds has important implications for astrobiology. The metallicity of the Magellanic Clouds is similar to galaxies in the earlier epochs of the Universe, thus the presence of COMs in the LMC and SMC indicates that a similar prebiotic chemistry leading to the emergence of life, as it happened on Earth, is possible in lowmetallicity systems in the earlier Universe.

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Deep, Broadband Spectral Line Surveys of Molecule-rich Interstellar Clouds

Cited by 29 publications

References 268 publications

A sensitive λ 3 mm line survey of L483

A sensitive λ 3 mm line survey of L483

Carbon-grain Sublimation: A New Top-down Component of Protostellar Chemistry

Complex Organic Molecules in Star-Forming Regions of the Magellanic Clouds

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