Blazars spectral properties at 74 MHz

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.

8 pages, 12 figures, 1 table, ApJS accepted (version pre-proof corrections)

References in corpus (10)

• LOFAR: The LOw-Frequency ARray
• Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Likelihoods and Parameters from the WMAP data
• The Murchison Widefield Array: the Square Kilometre Array Precursor at low radio frequencies
• CRATES: An All-Sky Survey of Flat-Spectrum Radio Sources
• The VLA Low-frequency Sky Survey
• Roma-BZCAT: A multifrequency catalogue of Blazars
• A Unified Catalog of Radio Objects Detected by NVSS, FIRST, WENSS, GB6, and SDSS
• Unveiling the nature of the unidentified gamma-ray sources I: a new method for the association of gamma-ray blazars
• Unveiling the nature of the unidentified gamma-ray sources III: gamma-ray blazar-like counterparts at low radio frequencies
• Chandra View of the Warm-Hot IGM toward 1ES 1553+113: Absorption Line Detections and Identifications (Paper I)

Cited by in corpus (24)

• The WISE Blazar-Like Radio-Loud Sources: An All-Sky Catalog Of Candidate Gamma-Ray Blazars
• The LOFAR LBA Sky Survey I. survey description and preliminary data release
• Two new catalogs of blazar candidates in the WISE infrared sky
• Optical spectroscopic observations of $\gamma$-ray blazar candidates VI. Further observations from TNG, WHT, OAN, SOAR and Magellan telescopes
• The Extragalactic Gamma-ray Sky in the Fermi era
• Optical spectroscopic observations of blazars and gamma-ray blazar candidates in the Sloan Digital Sky Survey Data Release Nine
• Mapping the particle acceleration in the cool core of the galaxy cluster RX J1720.1+2638
• Dark matter in the Reticulum II dSph: a radio search
• Refining the associations of the Fermi Large Area Telescope Source Catalogs
• The Infrared-Gamma-Ray Connection: A WISE View of the Extragalactic Gamma-Ray Sky
• High-energy sources at low radio frequency: the Murchison Widefield Array view of Fermi blazars
• The low-frequency radio catalog of flat spectrum sources
• Optical archival spectra of blazar candidates of uncertain type in the 3${}^{rd}$ Fermi Large Area Telescope Catalog
• Optical spectroscopic observations of gamma-ray blazar candidates VIII: the 2016-2017 follow up campaign carried out at SPM, NOT, KPNO and SOAR telescopes
• Mapping Jet-ISM Interactions in X-ray Binaries with ALMA: A GRS 1915$+$105 Case Study
• Radio Weak BL Lac objects in the Fermi era
• NuSTAR, Swift, and GROND observations of the flaring MeV blazar: PMN J0641$-$0320
• The Radio/Gamma Connection of Blazars from High to Low Radio Frequencies
• Synchrotron radiation from electrons with a pitch-angle distribution
• The $\gamma$-ray sky seen at X-ray energies I. Searching for the connection between X-rays and $\gamma$-rays in Fermi BL Lac objects
• Characterising the extended morphologies of BL Lacs at 144 MHz with LOFAR
• Further evidences of superluminal AGNs as $\gamma$-ray sources
• Radio spectral properties of cores and extended regions in blazars in the MHz regime
• A FLASH on Blazars: Capturing the Radio Realm of 4FGL Blazars with SKAO Pathfinders