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ALMA spectral survey of Supernova 1987A – molecular inventory, chemistry, dynamics and explosive nucleosynthesis

Matsuura, M., Indebetouw, R, Woosley, S, Bujarrabal, V, Abellan, F. J., McCray, R., Kamenetzky, J., Fransson, C., Barlow, M. J., Gomez, H. L., Cigan, P., De Looze, I., Spyromilio, J., Staveley-Smith, L., Zanardo, G., Roche, P., Larsson, J., Viti, S., van Loon, J. Th., Wheeler, J. C., Baes, M., Chevalier, R., Lundqvist, P., Marcaide, J. M., Dwek, E., Meixner, M., Ng, C. -Y., Sonneborn, G. and Yates, J. 2017. ALMA spectral survey of Supernova 1987A – molecular inventory, chemistry, dynamics and explosive nucleosynthesis. Monthly Notices of the Royal Astronomical Society 469 (3) , pp. 3347-3362. 10.1093/mnras/stx830

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We report the first molecular line survey of Supernova 1987A in the millimetre wavelength range. In the ALMA 210--300 and 340--360 GHz spectra, we detected cold (20--170 K) CO, 28SiO, HCO+ and SO, with weaker lines of 29SiO from ejecta. This is the first identification of HCO+ and SO in a young supernova remnant. We find a dip in the J=6--5 and 5--4 SiO line profiles, suggesting that the ejecta morphology is likely elongated. The difference of the CO and SiO line profiles is consistent with hydrodynamic simulations, which show that Rayleigh-Taylor instabilities cause mixing of gas, with heavier elements much more disturbed, making more elongated structure. We obtained isotopologue ratios of 28SiO/29SiO>13, 28SiO/30SiO>14, and 12CO/13CO>21, with the most likely limits of 28SiO/29SiO>128, 28SiO/30SiO>189. Low 29Si and 30Si abundances in SN 1987A are consistent with nucleosynthesis models that show inefficient formation of neutron-rich isotopes in a low metallicity environment, such as the Large Magellanic Cloud. The deduced large mass of HCO+ (~5x10^-6 Msun) and small SiS mass (<6x10^-5 Msun) might be explained by some mixing of elements immediately after the explosion. The mixing might have caused some hydrogen from the envelope to sink into carbon and oxygen-rich zones after the explosion, enabling the formation of a substantial mass of HCO+. Oxygen atoms may have penetrated into silicon and sulphur zones, suppressing formation of SiS. Our ALMA observations open up a new window to investigate chemistry, dynamics and explosive-nucleosynthesis in supernovae.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Uncontrolled Keywords: Supernovae: individual: Supernova 1987A, ISM: abundances, ISM: molecules, ISM: supernova remnants, radio lines: ISM
Publisher: Oxford University Press
ISSN: 0035-8711
Date of First Compliant Deposit: 12 April 2017
Date of Acceptance: 31 March 2017
Last Modified: 26 Nov 2020 22:08

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