A FLASH on Blazars: Capturing the Radio Realm of 4FGL Blazars with SKAO Pathfinders

Abstract

This work investigates the multi-wavelength properties of 165 4FGL blazars from the Fermi-LAT fourth source catalogue, looking for with counterparts in the Australian SKA Pathfinder (ASKAP) First Large Absorption Survey in HI (FLASH) continuum. Using high-resolution data from FLASH and complementary radio datasets, combined with archival Atacama Large Millimeter Array (ALMA) observations, we perform detailed spectral energy distribution (SED) analyses across cm-to-mm wavelengths. Our findings reveal that most blazars exhibit re-triggered peaked spectra, indicative of emission dominated by a single emitting region. Additionally, we identify strong correlations between radio and gamma-ray luminosities, highlighting the significant role of relativistic jets in these active galactic nuclei. The inclusion of spectroscopic redshifts from Sloan Digital Sky Survey (SDSS) and Gaia enables a comprehensive analysis of the evolutionary trends and physical characteristics of the sources. Furthermore, we report a tight Radio-X-ray Correlation for Flat Spectrum Radio Quasars, contrasting with the more scattered behaviour observed in BL-Lacs, reflecting their distinct accretion and jet-driving mechanisms. These results provide critical insights into the physics of blazars and their environments, paving the way for future studies with next-generation facilities like the SKA Observatory (SKAO) for radio observations and Cherenkov Telescope Array for gamma-ray studies.

15 pages, 9 figures, Accepted for publication in Astronomy & Astrophysics (A&A). DOI: 10.1051/0004-6361/202554523

References in corpus (16)

• The SRG/eROSITA all-sky survey: First X-ray catalogues and data release of the western Galactic hemisphere
• The Rapid ASKAP Continuum Survey I: Design and First Results
• The faint radio sky: radio astronomy becomes mainstream
• The Rapid ASKAP Continuum Survey Paper II: First Stokes I Source Catalogue Data Release
• Extragalactic Peaked-Spectrum Radio Sources at Low Frequencies
• The Lockman Hole project: LOFAR observations and spectral index properties of low-frequency radio sources
• The Murchison Widefield Array Commissioning Survey: A Low-Frequency Catalogue of 14,110 Compact Radio Sources over 6,100 Square Degrees
• Constraining the nature of High Frequency Peakers. I. The spectral variability
• The Rapid ASKAP Continuum Survey IV: continuum imaging at 1367.5 MHz and the first data release of RACS-mid
• Unveiling the nature of the unidentified gamma-ray sources VI: gamma-ray blazar candidates in the WISH survey and their radio properties
• The Spectra of IceCube Neutrino (SIN) candidate sources -- II. Source Characterisation
• PKS 1424+240: yet another masquerading BL Lac object as a possible IceCube neutrino source
• Extragalactic Peaked-Spectrum Radio Sources at Low-Frequencies are Young Radio Galaxies
• Mapping HI 21-cm in the Klemola 31 group at z = 0.029: emission and absorption towards PKS2020-370
• RadioSED I: Bayesian inference of radio SEDs from inhomogeneous surveys
• Emergence of a new HI 21-cm absorption component at z~1.1726 towards the gamma-ray blazar PKS~2355-106