The remnant of supernova 1987A resolved at 3-mm wavelength^⋆

M. Lakićević^1,2, G. Zanardo³, J. Th. van Loon², L. Staveley-Smith^3,6, T. Potter³, C.-Y. Ng⁴ and B. M. Gaensler^5,6

¹ European Organization for Astronomical Research in the Southern Hemisphere (ESO), Karl-Schwarzschild-Str. 2, 85748 Garching b. München, Germany
e-mail: mlakicev@eso.org
² Astrophysics Group, Lennard-Jones Laboratories, Keele University, Staffordshire ST5 5BG, UK
³ International Centre for Radio Astronomy Research (ICRAR), M468, University of Western Australia, Crawley, WA 6009, Australia
⁴ Department of Physics, McGill University, Montréal, QC H3A 2T8, Canada
⁵ Sydney Institute for Astronomy (SIfA), School of Physics, The University of Sydney, NSW 2006, Australia
⁶ ARC Centre of Excellence for All-sky Astrophysics (CAASTRO), Australia

Received: 27 January 2012
Accepted: 22 March 2012

Abstract

Context. The proximity of core-collapse supernova 1987A (SN 1987A) in the Large Magellanic Cloud (LMC) and its rapid evolution make it a unique case study of the development of a young supernova remnant.

Aims. We aim at resolving the remnant of SN 1987A for the first time in the 3-mm band (at 94 GHz).

Methods. We observed the source at 3-mm wavelength with a 750-m configuration of the Australia Telescope Compact Array (ATCA). We compared the image with a recent 3-cm image and with archival X-ray images.

Results. We present a diffraction-limited image with a resolution of 0.′′7, revealing the ring structure seen at lower frequencies and at other wavebands. The emission peaks in the eastern part of the ring. The 3-mm image bears resemblance to early X-ray images (from 1999–2000). We place an upper limit of 1 mJy (2σ) on any discrete source of emission in the centre (inside of the ring). The integrated flux density at 3 mm has doubled over the six years since the previous observations at 3 mm.

Conclusions. At 3 mm – i.e. within the operational domain of the Atacama Large Millimeter/submillimeter Array (ALMA) – SN 1987A appears to be dominated by synchrotron radiation from the inner rim of the equatorial ring, characterised by moderately weak shocks. There is no clear sign of emission of a different nature, but the current limits do not rule out such component altogether.