High-resolution radio observations of SNR 1987A at high frequencies

Abstract

We present new imaging observations of the remnant of Supernova (SN) 1987A at 44 GHz, performed in 2011 with the Australia Telescope Compact Array (ATCA). The $0\farcs35\times0\farcs23$ resolution of the diffraction-limited image is the highest achieved to date in high-dynamic range. We also present a new ATCA image at 18 GHz derived from 2011 observations, which is super-resolved to $0\farcs25$. The flux density is 40$\pm$2 mJy at 44 GHz and 81$\pm$6 mJy at 18 GHz. At both frequencies, the remnant exhibits a ring-like emission with two prominent lobes, and an east-west brightness asymmetry that peaks on the eastern lobe. A central feature of fainter emission appears at 44 GHz. A comparison with previous ATCA observations at 18 and 36 GHz highlights higher expansion velocities of the remnant eastern side. The 18-44 GHz spectral index is $\alpha =-0.80$ ($S_{\nu }\propto {\nu }^{\alpha }$). The spectral index map suggests slightly steeper values at the brightest sites on the eastern lobe, whereas flatter values are associated with the inner regions. The remnant morphology at 44 GHz generally matches the structure seen with contemporaneous X-ray and H$\alpha$ observations. Unlike the H$\alpha$ emission, both the radio and X-ray emission peaks on the eastern lobe. The regions of flatter spectral index align and partially overlap with the optically-visible ejecta. Simple free-free absorption models suggest that emission from a pulsar wind nebula or a compact source inside the remnant may now be detectable at high frequencies, or at low frequencies if there are holes in the ionised component of the ejecta.

arXiv commentReferences updated. High resolution version may be found at http://ict.icrar.org/store/staff/gio/Papers/Zanardo_2013.pdf

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• Pushing 1D CCSNe to explosions: model and SN 1987A
• High angular resolution ALMA images of dust and molecules in the SN 1987A ejecta
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• The 30-Year Search for the Compact Object in SN 1987A
• Carbon Monoxide in the Cold Debris of Supernova 1987A
• Evolution of the Radio Remnant of Supernova 1987A: Morphological Changes from Day 7000
• Indication of a Pulsar Wind Nebula in the hard X-ray emission from SN 1987A
• Multi-dimensional simulations of the expanding supernova remnant of SN 1987A
• The Re-Acceleration of the Shock Wave in the Radio Remnant of SN 1987A
• Forming equatorial rings around dying stars
• Detection of Linear Polarization in the Radio Remnant of Supernova 1987A
• Exploring the Gamma-Ray Emissivity of Young Supernova Remnants I: Hadronic Emission
• SN 1986J VLBI. III. The Central Component Becomes Dominant
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• Mid-infrared imaging of Supernova 1987A
• ATCA Study of Small Magellanic Cloud Supernova Remnant 1E 0102.2-7219
• UV spectroscopy of the blue supergiant SBW1: the remarkably weak wind of a SN 1987A analog
• SN 1978K: An evolved supernova outside our Local Group detected at millimetre wavelengths
• Polarized radio emission unveils the structure of the pre-supernova circumstellar magnetic field and the radio emission in SN1987A
• Near-infrared evolution of the equatorial ring of SN 1987A
• Linking gamma-ray spectra of supernova remnants to the cosmic ray injection properties in the aftermath of supernovae
• Radio Observations of Supernova 1987A
• The Radio Remnant of Supernova 1987A - A Broader View
• The radio remnant of Supernova 1987A at high frequencies and high resolution
• Bayesian Multi-wavelength Imaging of the LMC SN1987A with SRG/eROSITA