Speaker
Description
We investigate the radio and multi-wavelength properties of 165 blazars from the Fermi-LAT 4FGL catalogue, cross-matched with the ASKAP FLASH continuum survey. The sample includes FSRQs, BL Lacs and blazar candidates of uncertain type, with complementary coverage from RACS, GLEAM-X, AT20G, and ALMACAL, and archival optical/IR and X-ray data.
Radio spectral energy distributions were reconstructed using RadioSED, with at least 5 photometric detections per source. About 50% of the sample exhibit re-triggered peaked spectra, while 14% clearly deviate from this shape. The median rest-frame peak frequency is νpeak ≈ 4.6 GHz, with 55% peaking above 10 GHz, consistent with young or recently re-activated blazars. At low frequencies (<100 MHz), the median spectral index is α ≈ –0.54, indicating extended steep-spectrum emission likely from older lobes.
Strong correlations were identified between radio and gamma-ray luminosities: at 855 MHz, correlation coefficients are ρ ≈ 0.70 for the full sample, with ρ = 0.92 for FSRQs and ρ = 0.85 for BL Lacs. The median radio luminosity at 855 MHz is 2.5 × 10²⁶ W Hz⁻¹, while the median gamma-ray luminosity is 4.3 × 10²⁶ W Hz⁻¹. In the radio–X-ray plane (0.2–2.0 keV), a tight correlation is found for FSRQs (ρ ≈ 0.97 at 855 MHz, ρ ≈ 0.82 at 20 GHz), contrasting with the scattered behaviour of BL Lacs, reflecting their distinct accretion versus jet-driven regimes.
These results confirm that relativistic jets dominate the radio–gamma connection in blazars, while the radio–X-ray relation highlights differences between FSRQs and BL Lacs. FLASH blazar studies provide critical input for jet physics and AGN evolution, and establish a framework for future large-sample investigations with SKA pathfinders and the SKAO.
| Topics | Galaxy Evolution & AGN |
|---|