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High-resolution SOFIA/EXES Spectroscopy of SO₂ Gas in the Massive Young Stellar Object MonR2 IRS3: Implications for the Sulfur Budget

Dungee, Ryan and Boogert, Adwin and DeWitt, Curtis N. and Montiel, Edward and Richter, Matthew J. and Barr, Andrew G. and Blake, Geoffrey A. and Charnley, Steven B. and Indriolo, Nick and Karska, Agata and Neufeld, David A. and Smith, Rachel L. and Tielens, Alexander G. G. M. (2018) High-resolution SOFIA/EXES Spectroscopy of SO₂ Gas in the Massive Young Stellar Object MonR2 IRS3: Implications for the Sulfur Budget. Astrophysical Journal Letters, 868 (1). Art. No. L10. ISSN 2041-8213. PMCID PMC6376201. doi:10.3847/2041-8213/aaeda9.

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Sulfur has been observed to be severely depleted in dense clouds leading to uncertainty in the molecules that contain it and the chemistry behind their evolution. Here, we aim to shed light on the sulfur chemistry in young stellar objects (YSOs) by using high-resolution infrared spectroscopy of absorption by the ν₃ rovibrational band of SO₂ obtained with the Echelon-Cross-Echelle Spectrograph on the Stratospheric Observatory for Infrared Astronomy. Using local thermodynamic equilibrium models we derive physical parameters for the SO₂ gas in the massive YSO MonR2 IRS3. This yields a SO₂/H abundance lower limit of 5.6 ± 0.5 × 10⁻⁷, or >4% of the cosmic sulfur budget, and an intrinsic line width (Doppler parameter) of b < 3.20 km s⁻¹). The small line widths and high temperature (T_(ex) = 234 ± 15 K) locate the gas in a relatively quiescent region near the YSO, presumably in the hot core where ices have evaporated. This sublimation unlocks a volatile sulfur reservoir (e.g., sulfur allotropes as detected abundantly in comet 67P/Churyumov–Gerasimenko), which is followed by SO₂ formation by warm, dense gas-phase chemistry. The narrowness of the lines makes formation of SO₂ from sulfur sputtered off grains in shocks less likely toward MonR2 IRS3.

Item Type:Article
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URLURL TypeDescription CentralArticle Paper
Dungee, Ryan0000-0001-6669-0217
Boogert, Adwin0000-0001-9344-0096
Montiel, Edward0000-0003-2553-4474
Richter, Matthew J.0000-0002-8594-2122
Barr, Andrew G.0000-0003-4909-2770
Blake, Geoffrey A.0000-0003-0787-1610
Indriolo, Nick0000-0001-8533-6440
Karska, Agata0000-0001-8913-925X
Neufeld, David A.0000-0001-8341-1646
Additional Information:© 2018 The American Astronomical Society. Received 2018 September 4; revised 2018 October 17; accepted 2018 October 26; published 2018 November 16. Based in part on observations made with the NASA/DLR Stratospheric Observatory for Infrared Astronomy (SOFIA). SOFIA is jointly operated by the Universities Space Research Association, Inc. (USRA), under NASA contract NNA17BF53C, and the Deutsches SOFIA Institut (DSI) under DLR contract 50 OK 0901 to the University of Stuttgart. Financial support for this work was provided by NASA through award No. SOF 04-153 issued by USRA. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. A.K. acknowledges support from the Polish National Science Center grant 2016/21/D/ST9/01098. R.L.S. gratefully acknowledges support under NASA Emerging Worlds grant NNX17AE34G. Facility: SOFIA. - Software: Redux (Clarke et al. 2015), emcee (Foreman-Mackey et al. 2013), PSG (Villanueva et al. 2018).
Group:Astronomy Department
Funding AgencyGrant Number
Deutsches Zentrum für Luft- und Raumfahrt (DLR)50 OK 0901
NASASOF 04-153
W. M. Keck FoundationUNSPECIFIED
National Science Centre (Poland)2016/21/D/ST9/01098
Subject Keywords:astrochemistry – infrared: ISM – ISM: individual objects (MonR2 IRS3) – ISM: molecules
Issue or Number:1
PubMed Central ID:PMC6376201
Record Number:CaltechAUTHORS:20181120-103333961
Persistent URL:
Official Citation:Ryan Dungee et al 2018 ApJL 868 L10
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:91068
Deposited By: Tony Diaz
Deposited On:20 Nov 2018 19:00
Last Modified:16 Feb 2022 23:47

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