Study of a Giant Large Magellanic Cloud Supernova Remnant, Veliki (J0450.4−7050)

Abstract

We present a high-resolution radio-continuum view and multi-frequency analysis of the Large Magellanic Cloud (LMC) Supernova Remnant (SNR) J0450.4−7050, which we nicknamed Veliki. These high-resolution observations reveal a larger extent than previously measured, making J0450.4−7050 one of the largest SNRs that we know of. Additionally, we observe a higher than expected radio surface brightness and an unusually flat spectral index (α = −0.26 ± 0.02), with little spectral variation over the remnant. We observe a bright Hα shell indicating significant cooling over the remnant, but also an excess of [Oiii] on the eastern shock front. We investigate several theoretical scenarios to explain the emission and radio evolution of J0450.4−7050 in the context of the LMC environment, and determine that this is most likely an older, predominantly radiative, SNR with a higher shock compression ratio, which gives a flatter non-thermal spectrum in combination with thermal (bremsstrahlung) emission contribution.