2012A&A...541L...2L

The proximity of core-collapse supernova 1987A (SN1987A) in the Large Magellanic Cloud (LMC) and its rapid evolution make it a unique case study of the development of a young supernova remnant. We aim at resolving the remnant of SN1987A for the first time in the 3-mm band (at 94GHz). 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. 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 3mm has doubled over the six years since the previous observations at 3mm. At 3mm - i.e. within the operational domain of the Atacama Large Millimeter/submillimeter Array (ALMA) - SN1987A 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.