Blazars spectral properties at 74 MHz

TL;DR

This study investigates the spectral properties of blazars at 74 MHz using VLSS data, revealing flat spectra and providing insights into the blazar-radio galaxy unification scenario.

Contribution

First systematic analysis of blazar spectra at frequencies below 100 MHz, confirming detection at 74 MHz and exploring implications for unification models.

Findings

Blazars are detected at 74 MHz in VLSS.

Blazars exhibit flat radio spectra (~0.5) at low frequencies.

Results support the blazar-radio galaxy unification scenario.

Abstract

Blazars are the most extreme class of active galactic nuclei (AGNs). Despite a previous investigation at 102 MHz for a small sample of BL Lacs and our recent analysis of blazars detected in the Westerbork Northern Sky Survey (WENSS), a systematic study of the blazar spectral properties at frequencies below 100 MHz has been never carried out. In this paper, we present the first analysis of the radio spectral behavior of blazars based on the recent Very Large Array Low-Frequency Sky Survey (VLSS) at 74 MHz. We search for blazar counterparts in the VLSS catalog confirming that they are detected at 74 MHz. We then show that blazars present radio flat spectra {(i.e., radio spectral indices ~0.5)} when evaluated also about an order of magnitude in frequency lower than previous analyses. Finally, we discuss the implications of our findings in the context of the blazars - radio galaxies connection since the low frequency radio data provide a new diagnostic tool to verify the expectations of the unification scenario for radio-loud active galaxies.