The properties of powerful radio sources at 90 GHz

TL;DR

This study observes powerful radio sources at 90 GHz to analyze their high-frequency spectral properties, revealing flat-spectrum cores, detected jets, and diverse hotspot spectra, with implications for future ALMA studies.

Contribution

First comprehensive analysis of high-frequency spectra of compact radio galaxy components using 90 GHz observations, expanding understanding of their spectral behaviors.

Findings

Cores remain flat-spectrum up to 90 GHz

Jets detected at 90 GHz for the first time in some sources

Hotspots show diverse spectral properties

Abstract

We have observed a small sample of powerful double radio sources (radio galaxies and quasars) at frequencies around 90 GHz with the BIMA millimetre array, with the intention of constraining the resolved high-frequency spectra of radio galaxies. When combined with other sources we have previously observed and with data from the BIMA archive, these observations allow us for the first time to make general statements about the high-frequency behaviour of compact components of radio galaxies -- cores, jets and hotspots. We find that cores in our sample remain flat-spectrum up to 90 GHz; jets in some of our targets are detected at 90 GHz for the first time in our new observations; and hotspots are found to be almost universal, but show a wide range of spectral properties. Emission from the extended lobes of radio galaxies is detected in a few cases and shows rough consistency with the expectations from standard spectral ageing models, though our ability to probe this in detail is limited by the sensitivity of BIMA. We briefly discuss the prospects for radio-galaxy astrophysics with ALMA.