Observations of M87 and Hydra A at 90 GHz

TL;DR

This study presents high-resolution 90 GHz observations of M87 and Hydra A, analyzing their spectral properties to understand particle energy losses and re-acceleration in their jets.

Contribution

It provides new 90 GHz data combined with archival VLA data, revealing differences in spectral steepening and particle energy losses in the jets of M87 and Hydra A.

Findings

M87 shows weak spectral steepening, indicating possible re-acceleration or low energy losses.

Hydra A exhibits strong spectral steepening, suggesting significant energy losses.

Differences in jet length may explain the spectral behavior differences.

Abstract

This paper presents new observations of the AGNs M87 and Hydra A at 90 GHz made with the MUSTANG bolometer array on the Green Bank Telescope at 8.5" resolution. A spectral analysis is performed combining this new data and archival VLA data on these objects at longer wavelengths. This analysis can detect variations in spectral index and curvature expected from energy losses in the radiating particles. M87 shows only weak evidence for steepening of the spectrum along the jet suggesting either re-acceleration of the relativistic particles in the jet or insufficient losses to affect the spectrum at 90 GHz. The jets in Hydra A show strong steepening as they move from the nucleus suggesting unbalanced losses of the higher energy relativistic particles. The difference between these two sources may be accounted for by the different lengths over which the jets are observable, 2 kpc for M87 and 45 kpc for Hydra A.