A MeerKAT morphological and spectral index study of M87

Abstract

Messier 87 (M87) is a spectacular radio galaxy located in our cosmic backyard. Its proximity has allowed astronomers to study it in detail across the electromagnetic spectrum. M87 shows a complex structure in the radio continuum made up of a bright core, jets and a diffuse halo. High fidelity imaging of this bright (> 300$\, $Jy), complex source is necessary to understanding its evolution. MeerKAT’s sensitivity and spatial resolution make it an ideal instrument to study M87's extended, diffuse radio structure. We present the MeerKAT 1.28$\, $GHz total-intensity map, in-band spectral index image, and an analysis of its complex morphological structure. A comparison of the MeerKAT map with the VLA map is conducted, comparing all key features, by means of a two point spectral index map at the respective frequencies, 1.28$\, $GHz and 327$\, $MHz. Our results 1) verify the structures seen in the VLA 327$\, $MHz image, made using maximum entropy techniques 2) show the first spectral index of the filamentary structures 3) demonstrate the ability of MeerKAT to map complex, diffuse structures at higher frequencies than before, extending the frequency range to enable for more detailed, spatially resolved spectral analysis. In conclusion, we find results that are consistent with what has been observed about M87, that it is an active galaxy with a steady spectral variation across a large radio frequency range.