ALMA spectral survey of Supernova 1987A - molecular inventory, chemistry, dynamics and explosive nucleosynthesis
Abstract
We report the first molecular line survey of Supernova 1987A in the millimetre wavelength range. In the Atacama Large Millimeter/submillimeter Array (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+ (∼5 × 10-6 M⊙) and small SiS mass (<6 × 10-5 M⊙) 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.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- August 2017
- DOI:
- 10.1093/mnras/stx830
- arXiv:
- arXiv:1704.02324
- Bibcode:
- 2017MNRAS.469.3347M
- Keywords:
-
- supernovae: individual: Supernova 1987A;
- ISM: abundances;
- ISM: molecules;
- ISM: supernova remnants;
- radio lines: ISM;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- Accepted by MNRAS, 16 pages