Chemistry of the High-mass Protostellar Molecular Clump IRAS 16562–3959

Abstract

We present molecular line observations of the high-mass molecular clump IRAS 16562−3959 taken at 3 mm using the Atacama Large Millimeter/submillimeter Array (ALMA) at 1. 7 angular resolution (0.014 pc spatial resolution). This clump hosts the actively accreting high-mass young stellar object (HMYSO) G345.4938+01.4677, associated with a hypercompact Hii region. We identify and analyze emission lines from 22 molecular species (encompassing 34 isomers) and classify them into two groups, depending on their spatial distribution within the clump. One of these groups gathers shock tracers (e.g., SiO, SO, HNCO) and species formed in dust grains like methanol (CH 3 OH), ethenone or ketene (H 2 CCO), and acetaldehyde (CH 3 CHO). The second group collects species resembling more the dust continuum emission morphology and are formed mainly in the gas-phase, like hydrocarbons (CCH, c-C 3 H 2 , CH 3 CCH), cyanopolyynes (HC 3 N and HC 5 N) and cyanides (HCN and CH 3 C 3 N). Emission from complex organic molecules (COMs) like CH 3 OH, propanenitrile (CH 3 CH 2 CN), and methoxymethane (CH 3 OCH 3 ) arise from gas in the vicinity of a hot molecular core (T 100 K) associated with the HMYSO. Other COMs such as propyne (CH 3 CCH), acrylonitrile (CH 2 CHCN), and acetaldehyde seem to better trace warm (T 80 K) dense gas. In addition, deuterated ammonia (NH 2 D) is detected mostly in the outskirts of IRAS 16562−3959 and associated with near-infrared dark globules, probably gaseous remnants of the clump's prestellar phase. The spatial distribution of molecules in IRAS 16562−3959 supports the view that in protostellar clumps, chemical tracers associated with different evolutionary stages -starless to hot cores/Hii regions -exist coevally.1, 7 2 98.4976 9.2 Sulfur dioxide 9 SO 2 J KaKc = 8 3,5 → 9 2,8 86.6430 55.2 J KaKc = 20 2,18 → 21 1,21 86.8329 207.8 J KaKc = 7 3,5 → 8 2,6 97.7067 47.8 J KaKc = 28 7,21 → 29 6,24 98.9817 493.7 J KaKc = 29 4,26 → 28 5,23 99.3978 440.7 Ammonia (azane) 10 NH 2 D J KaKc = 1 1,1 , 0 s → 1 0,1 , 0 a 85.9223 20.7 Silicon monoxide 11 SiO J = 2 → 1 86.8499 6.3 12 29 SiO J = 2 → 1 85.7612 6.2 13 30 SiO J = 2 → 1 84.7489 b11 6.1 Propyne (methylacetylene) 13 CH 3 CCH J, K = 5, 3 → 4, 3 85.4467 77.3 J, K = 5, 2 → 4, 2 85.4548 41.2 J, K = 5, 1 → 4, 1 85.4605 b1 19.5 J, K = 5, 0 → 4, 0 85.4605 b1 12.3 Formylium 14 H 13 CO + J = 1 → 0 86.7582 b6 4.2 15 HC 18 O + J = 1 → 0 85.1660 4.1 Cyclopropenylidene Table 1 continued on next page J KaKc = 11 0,11 → 10 0,10 96.9245 28.1 J KaKc = 11 2,10 → 10 2,9 98.1824 32.8 J KaKc = 11 6,6 → 10 6,5 98.5293 b2 68.4 J KaKc = 11 6,5 → 10 6,4 98.5293 b2 68.4 J KaKc = 11 7,4 → 10 7,3 98.5293 b2 82.8 J KaKc = 11 7,5 → 10 7,4 98.5293 b2 82.8 J KaKc = 11 8,3 → 10 8,2 98.5385 b3 99.5 J KaKc = 11 8,4 → 10 8,3 98.5385 b3 99.5 J KaKc = 11 5,7 → 10 5,6 98.5385 b3 56.2 J KaKc = 11 5,6 → 10 5,5 98.5385 b3 56.2 J KaKc = 11 9,2 → 10 9,1 98.5493 b4 118.4 J KaKc = 11 9,3 → 10 9,2 98.5493 b4 118.4 Table 1 continued on next page J KaKc = 11 4,8 → 10 4,7 98.5701 b5 46.2 J KaKc = 11 4,7 → 10 4,6 98.5712 b...

Rotational spectrum simulations of asymmetric tops in an astrochemical context

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Methyl acetylene in G331.512-0.103: Looking at massive star formation through the lens of chemistry

“…as well as its morphology and evolutionary stage (e.g., Wyrowski et al 1999;Beuther et al 2005;Guzmán et al 2018). In this context, experimental and theoretical rotational spectroscopy share a symbiotic relationship that is fundamental to broaden our percipience of the physics and chemistry of the ISM (see, e.g., Puzzarini 2017; Puzzarini and Barone 2020; Cerqueira et al 2020;Santos et al 2020).…”

“…Later, Lovas clouds. Since its first detection, CH 3 CCH has been extensively studied toward star-forming regions (e.g., Zhang et al 2014;Taniguchi et al 2018;Guzmán et al 2018;Bøgelund et al 2019;Calcutt et al 2019), and has proven to be a reliable tracer of their physical conditions (e.g., Bergin et al 1994). It has also been observed toward extagalactic sources, such as M 82, NGC 253, and NGC 1068 (Mauersberger et al, 1991;Qiu et al, 2020), and even toward a planetary nebula, as recently reported by Schmidt and Ziurys (2019).…”

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