Astrophys. J., 796, 82 (2014/December-1)
Spectral and morphological analysis of the remnant of supernova 1987A with ALMA and ATCA.
ZANARDO G., STAVELEY-SMITH L., INDEBETOUW R., CHEVALIER R.A., MATSUURA M., GAENSLER B.M., BARLOW M.J., FRANSSON C., MANCHESTER R.N., BAES M., KAMENETZKY J.R., LAKICEVIC M., LUNDQVIST P., MARCAIDE J.M., MARTI-VIDAL I., MEIXNER M., NG C.-Y., PARK S., SONNEBORN G., SPYROMILIO J. and VAN LOON J.Th.
Abstract (from CDS):
We present a comprehensive spectral and morphological analysis of the remnant of supernova (SN) 1987A with the Australia Telescope Compact Array (ATCA) and the Atacama Large Millimeter/submillimeter Array (ALMA). The non-thermal and thermal components of the radio emission are investigated in images from 94 to 672 GHz (λ 3.2 mm to 450 µm), with the assistance of a high-resolution 44 GHz synchrotron template from the ATCA, and a dust template from ALMA observations at 672 GHz. An analysis of the emission distribution over the equatorial ring in images from 44 to 345 GHz highlights a gradual decrease of the east-to-west asymmetry ratio with frequency. We attribute this to the shorter synchrotron lifetime at high frequencies. Across the transition from radio to far infrared, both the synchrotron/dust-subtracted images and the spectral energy distribution (SED) suggest additional emission beside the main synchrotron component (Sν∝ν–0.73) and the thermal component originating from dust grains at T ∼ 22 K. This excess could be due to free-free flux or emission from grains of colder dust. However, a second flat-spectrum synchrotron component appears to better fit the SED, implying that the emission could be attributed to a pulsar wind nebula (PWN). The residual emission is mainly localized west of the SN site, as the spectral analysis yields -0.4 ≲ α ≲ -0.1 across the western regions, with α ∼ 0 around the central region. If there is a PWN in the remnant interior, these data suggest that the pulsar may be offset westward from the SN position.
ISM: supernova remnants - radiation mechanisms: non-thermal - radiation mechanisms: thermal - radio continuum: general - stars: neutron - supernovae: individual: SN 1987A
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