Milliarcsecond Structures of Variable Peaked-Spectrum Sources

TL;DR

This study uses VLBI imaging to analyze the milliarcsecond structures of variable peaked-spectrum radio sources, confirming spectral variability as a tool for understanding their small-scale structures and activity.

Contribution

It demonstrates the effectiveness of spectral variability in predicting radio source morphology and provides detailed imaging of two variable PS sources, revealing their structures and activity.

Findings

MRC0225-065 is a young radio source with a core and lobes separated by 430pc.

PMNJ0322-4820 is unresolved and identified as a blazar with recent flaring activity.

Spectral variability predictions align with VLBI imaging results.

Abstract

Spectral variability offers a new technique to identify small scale structures from scintillation, as well as determining the absorption mechanism for peaked-spectrum (PS) radio sources. In this paper, we present very long baseline interferometry (VLBI) imaging using the Long Baseline Array (LBA) of two PS sources, MRC0225-065 and PMNJ0322-4820, identified as spectrally variable from observations with the Murchison Widefield Array (MWA). We compare expected milliarcsecond structures based on the detected spectral variability with direct LBA imaging. We find MRC0225-065 is resolved into three components, a bright core and two fainter lobes, roughly 430pc projected separation. A comprehensive analysis of the magnetic field, host galaxy properties, and spectral analysis implies that MRC0225-065 is a young radio source with recent jet activity over the last 10^2-10^3years. We find PMNJ0322-4820 is unresolved on milliarcsecond scales. We conclude PMNJ0322-4820 is a blazar with flaring activity detected in 2014 with the MWA. We use spectral variability to predict morphology and find these predictions consistent with the structures revealed by our LBA images.