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High angular resolution ALMA images of dust and molecules in the SN 1987A ejecta

Cigan, Phil, Matsuura, Mikako, Gomez, Haley L., Indebetouw, Remy, Abellán, Fran, Gabler, Michael, Richards, Anita, Alp, Dennis, Davis, Timothy A., Janka, Hans-Thomas, Spyromilio, Jason, Barlow, M. J., Burrows, David, Dwek, Eli, Fransson, Claes, Gaensler, Bryan, Larsson, Josefin, Bouchet, P., Lundqvist, Peter, Marcaide, J. M., Ng, C.-Y., Park, Sangwook, Roche, Pat, Loon, Jacco Th. van, Wheeler, J. C. and Zanardo, Giovanna 2019. High angular resolution ALMA images of dust and molecules in the SN 1987A ejecta. Astrophysical Journal 886 (1) , 51. 10.3847/1538-4357/ab4b46

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Abstract

We present high angular resolution (~80 mas) ALMA continuum images of the SN 1987A system, together with CO J = 2 $\to $ 1, J = 6 $\to $ 5, and SiO J = 5 $\to $ 4 to J = 7 $\to $ 6 images, which clearly resolve the ejecta (dust continuum and molecules) and ring (synchrotron continuum) components. Dust in the ejecta is asymmetric and clumpy, and overall the dust fills the spatial void seen in Hα images, filling that region with material from heavier elements. The dust clumps generally fill the space where CO J = 6 $\to $ 5 is fainter, tentatively indicating that these dust clumps and CO are locationally and chemically linked. In these regions, carbonaceous dust grains might have formed after dissociation of CO. The dust grains would have cooled by radiation, and subsequent collisions of grains with gas would also cool the gas, suppressing the CO J = 6 $\to $ 5 intensity. The data show a dust peak spatially coincident with the molecular hole seen in previous ALMA CO J = 2 $\to $ 1 and SiO J = 5 $\to $ 4 images. That dust peak, combined with CO and SiO line spectra, suggests that the dust and gas could be at higher temperatures than the surrounding material, though higher density cannot be totally excluded. One of the possibilities is that a compact source provides additional heat at that location. Fits to the far-infrared–millimeter spectral energy distribution give ejecta dust temperatures of 18–23 K. We revise the ejecta dust mass to M dust = 0.2–0.4 ${M}_{\odot }$ for carbon or silicate grains, or a maximum of <0.7 ${M}_{\odot }$ for a mixture of grain species, using the predicted nucleosynthesis yields as an upper limit.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Publisher: American Astronomical Society
ISSN: 0004-637X
Date of First Compliant Deposit: 14 November 2019
Date of Acceptance: 3 October 2019
Last Modified: 24 Nov 2020 23:09
URI: http://orca.cf.ac.uk/id/eprint/126815

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