Low-frequency observations of the Giant Radio Galaxy NGC 6251

Abstract

We present LOFAR observations at 150 MHz of the borderline FRI/FRII giant radio galaxy NGC 6251. This paper presents the most sensitive and highest-resolution images of NGC 6251 at these frequencies to date, revealing for the first time a low-surface-brightness extension to the northern lobe, and a possible backflow associated with the southern lobe. The integrated spectra of components of NGC 6251 are consistent with previous measurements at higher frequencies, similar to results from other LOFAR studies of nearby radio galaxies. We find the outer structures of NGC 6251 to be either at equipartition or slightly electron dominated, similar to those of FRII sources rather than FRIs; but this conclusion remains tentative because of uncertainties associated with the geometry and the extrapolation of X-ray measurements to determine the external pressure distribution on the scale of the outer lobes. We place lower limits on the ages of the extension of the northern lobe and the backflow of the southern lobe of $t\gtrsim 250$ Myr and $t\gtrsim 210$ Myr respectively. We present the first detection of polarisation at 150 MHz in NGC 6251. Taking advantage of the high Faraday resolution of LOFAR, we place an upper limit on the magnetic field in the group of $B<0.2({\Lambda }_B/10\mathrm{kpc}{)}^{-0.5}\mu$G for a coherence scale of ${\Lambda }_B<60\mathrm{kpc}$ and $B<13\mu$G for ${\Lambda }_B=240$ kpc.

arXiv comment19 pages, 17 figures; accepted by MNRAS

References in corpus (59)

• Astropy: A Community Python Package for Astronomy
• MultiNest: an efficient and robust Bayesian inference tool for cosmology and particle physics
• LOFAR: The LOw-Frequency ARray
• Multimodal nested sampling: an efficient and robust alternative to MCMC methods for astronomical data analysis
• Fermi Large Area Telescope Second Source Catalog
• Fermi Large Area Telescope First Source Catalog
• The Murchison Widefield Array: the Square Kilometre Array Precursor at low radio frequencies
• A Cosmology Calculator for the World Wide Web
• Importance Nested Sampling and the MultiNest Algorithm
• Faraday Rotation Measure Synthesis
• An X-ray study of magnetic field strengths and particle content in FRII radio sources
• A broadband flux scale for low frequency radio telescopes
• LOFAR facet calibration
• Dynamical models for jet deceleration in the radio galaxy 3C 31
• Revisiting the Fanaroff-Riley dichotomy and radio-galaxy morphology with the LOFAR Two-Metre Sky Survey (LoTSS)
• Calibrating High-Precision Faraday Rotation Measurements for LOFAR and the Next Generation of Low-Frequency Radio Telescopes
• A Chandra observation of the X-ray environment and jet of 3C31
• LOFAR/H-ATLAS: A deep low-frequency survey of the Herschel-ATLAS North Galactic Pole field
• Giant Radio Sources
• An XMM-Newton study of the environments, particle content and impact of low-power radio galaxies
• A Search for Warm/Hot Gas Filaments Between Pairs of SDSS Luminous Red Galaxies
• Particle content, radio-galaxy morphology and jet power: all radio-loud AGN are not equal
• Structures of the magnetoionic media around the FR I radio galaxies 3C 31 and Hydra A
• The LOFAR Multifrequency Snapshot Sky Survey (MSSS) I. Survey description and first results
• The nature of the low-frequency emission of M51: First observations of a nearby galaxy with LOFAR
• Rotation Measures of Radio Sources in Hot Galaxy Clusters
• X-ray emission from the nuclei, lobes and hot-gas environments of two FR-II radio galaxies
• A representative survey of the dynamics and energetics of FRII radio galaxies
• Faraday tomography of the local interstellar medium with LOFAR: Galactic foregrounds towards IC342
• A new sample of giant radio galaxies from the WENSS survey II - A multi-frequency radio study of a complete sample: Properties of the radio lobes and their environment
• X-ray-emitting Atmospheres of B2 Radio Galaxies
• Missing Baryons and the Warm-Hot Intergalactic Medium
• A multifrequency study of giant radio sources-II. Spectral ageing analysis of the lobes of selected sources
• Magnetic field strengths in the hot spots of 3C33 and 3C111
• Comparison of algorithms for determination of rotation measure and Faraday structure I. 1100 - 1400 MHz
• On the relationship between a giant radio galaxy MSH 05-22 and the ambient large-scale galaxy structure
• The intergalactic magnetic field probed by a giant radio galaxy
• The particle content of low-power radio galaxies in groups and clusters
• Chandra and XMM-Newton Observations of NGC 6251
• Giant radio galaxies - II. Tracers of large-scale structure
• VLSS Redux: Software Improvements applied to the Very Large Array Low-frequency Sky Survey
• Multifrequency observations of the jets in the radio galaxy NGC 315
• FR II radio galaxies at low frequencies I: morphology, magnetic field strength and energetics
• MRC B0319-454: Probing the large-scale structure with a giant radio galaxy
• Structure of the magnetoionic medium around the FR Class I radio galaxy 3C 449
• Unveiling the cause of hybrid morphology radio sources (HyMoRS)
• Multifrequency VLA observations of the FR I radio galaxy 3C 31: morphology, spectrum and magnetic field
• LOFAR reveals the giant: a low-frequency radio continuum study of the outflow in the nearby FR I radio galaxy 3C 31
• Polarized point sources in the LOFAR Two-meter Sky Survey: A preliminary catalog
• A new sample of large angular size radio galaxies. III. Statistics and evolution of the grown population
• Giant Radio Galaxies - old long-living quasars?
• Radio Lobes of Pictor A: an X-ray spatially resolved Study
• Wide-field LOFAR imaging of the field around the double-double radio galaxy B1834+620: A fresh view on a restarted AGN and doubeltjes
• The new sample of giant radio sources III. Statistical trends and correlations
• Testing Models of the Individual and Cosmological Evolutions of Powerful Radio Galaxies
• Suzaku X-ray Imaging of the Extended Lobe in the Giant Radio Galaxy NGC6251 Associated with the Fermi-LAT Source 2FGLJ1629.4+8236
• A study of the environments of large radio galaxies using SDSS
• Evidence for a significant mixture of electron/positron pairs in FRII jets constrained by cocoon dynamics
• What Happened to the NGC 6251 Counterjet?

Cited by in corpus (8)

• The Faraday Rotation Measure Grid of the LOFAR Two-metre Sky Survey: Data Release 2
• The POlarised GLEAM Survey (POGS) II: Results from an All-Sky Rotation Measure Synthesis Survey at Long Wavelengths
• The relation between the diffuse X-ray luminosity and the radio power of the central AGN in galaxy groups
• Hard X-ray selected giant radio galaxies -- III. The LOFAR view
• SAGAN-II : Molecular gas content of giant radio galaxies
• Collimation of the kiloparsec-scale radio jets in NGC 2663
• Spatial variations of magnetic field along active galactic nuclei jets on sub-pc to Mpc scales
• CS-ROMER: A novel compressed sensing framework for Faraday depth reconstruction