Unmasking the history of 3C 293 with LOFAR sub-arcsecond imaging

Abstract

Active galactic nuclei (AGNs) show episodic activity, evident in galaxies that exhibit restarted radio jets. These restarted jets can interact with their environment, leaving signatures on the radio spectral energy distribution. Tracing these signatures requires resolved spectral index measurements over a broad frequency range including low frequencies. We present such a study for the radio galaxy 3C 293. Using the International LOFAR telescope (ILT) we probed spatial scales as fine as ~0.2" at 144 MHz, and to constrain the spectrum we combined these data with Multi-Element Radio Linked Interferometer Network (MERLIN) and Very Large Array (VLA) archival data. In the inner lobes (~2 kpc), we detect the presence of a spectral turnover that peaks at ~225 MHz and is most likely caused by free-free absorption from the rich surrounding medium. We confirm that these inner lobes are part of a jet-dominated young radio source (spectral age $\lesssim$0.17 Myr), which is strongly interacting with the rich interstellar medium (ISM) of the host galaxy. The outer lobes (~100 kpc) have a spectral index of $\alpha$~0.6-0.8 from 144-4850 MHz with a remarkably uniform spatial distribution and only mild spectral curvature ($\Delta \alpha \lesssim$ 0.2). We propose that intermittent fuelling and jet flow disruptions are powering the mechanisms that keep the spectral index in the outer lobes from steepening and maintain the spatial uniformity of the spectral index. Overall, it appears that 3C 293 has gone through multiple (two to three) epochs of activity. This study adds 3C 293 to the new sub-group of restarted galaxies with short interruption time periods. This is the first time a spatially resolved study simultaneously studies a young source as well as the older outer lobes at such low frequencies. This illustrates the potential of the ILT to expand such studies to a larger sample of radio galaxies.

Accepted for a special issue of A&A on sub-arcsecond imaging with LOFAR

References in corpus (37)

• WSClean: an implementation of a fast, generic wide-field imager for radio astronomy
• The LOFAR Two-metre Sky Survey - I. Survey Description and Preliminary Data Release
• An optimized algorithm for multi-scale wideband deconvolution of radio astronomical images
• The LOFAR Two Meter Sky Survey: Deep Fields, I -- Direction-dependent calibration and imaging
• LOFAR observations of galaxy clusters in HETDEX
• In search of dying radio sources in the local universe
• Search and modelling of remnant radio galaxies in the LOFAR Lockman Hole field
• Sub-arcsecond imaging with the International LOFAR Telescope I. Foundational calibration strategy and pipeline
• A multifrequency study of giant radio sources-II. Spectral ageing analysis of the lobes of selected sources
• LBCS: the LOFAR Long-Baseline Calibrator Survey
• RAiSE III: 3C radio AGN energetics and composition
• Remnant radio-loud AGN in the Herschel-ATLAS field
• Three episodes of jet activity in the FRII radio galaxy B0925+420
• The duty cycle of radio galaxies revealed by LOFAR: remnant and restarted radio source populations in the Lockman Hole
• The life cycle of radio galaxies in the LOFAR Lockman Hole field
• Are young radio sources in equipartition?
• Subarcsecond international LOFAR radio images of Arp 220 at 150 MHz: A kpc-scale star forming disk surrounding nuclei with shocked outflows
• Subarcsecond international LOFAR radio images of the M82 nucleus at 118 MHz and 154 MHz
• Optical and radio properties of extragalactic radio sources with recurrent jet activity
• Jet-ISM Interaction in the Radio Galaxy 3C293: Jet-driven Shocks Heat ISM to Power X-ray and Molecular H2 emission
• Radio spectral properties and jet duty cycle in the restarted radio galaxy 3C388
• Jet Speeds in Wide Angle Tailed Radio Galaxies
• The LOFAR long baseline snapshot calibrator survey
• Sub-arcsecond imaging with the International LOFAR Telescope: II. Completion of the LOFAR Long-Baseline Calibrator Survey
• Investigating the spectral age problem with powerful radio galaxies
• Remnant Radio Galaxies Discovered in a Multi-frequency Survey
• The best of both worlds: Combining LOFAR and Apertif to derive resolved radio spectral index images
• The jet/wind outflow in Centaurus A: a local laboratory for AGN feedback
• An X-ray survey of the 2Jy sample. II: X-ray emission from extended structures
• Dynamical analysis of the complex radio structure in 3C 293: Clues on a rapid jet realignment in X-shaped radio galaxies
• A low-frequency study of recently identified double-double radio galaxies
• The parsec-scale HI outflows in powerful radio galaxies
• Discovery of a new, 2.2 Mpc Giant Radio Galaxy at a redshift of 0.57
• The LOFAR view of NGC 3998, a sputtering AGN
• LOFAR observations of 4C+19.44. On the discovery of low frequency spectral curvature in relativistic jet knots
• Multifrequency study of a double-double radio galaxy J0028+0035
• Restarted activity in the 3C328 radio galaxy

Cited by in corpus (14)

• Identifying active galactic nuclei via brightness temperature with sub-arcsecond International LOFAR Telescope observations
• Ionised gas outflows over the radio AGN life cycle
• Life cycle of cosmic-ray electrons in the intracluster medium
• The Dynamics and Energetics of Remnant and Restarting RLAGN
• Spatially resolved observations of outflows in the radio loud AGN of UGC 8782
• Search and analysis of giant radio galaxies with associated nuclei (SAGAN) V. Study of giant double-double radio galaxies from LoTSS DR2
• Redshift evolution of the HI detection rate in radio-loud active galactic nuclei
• New filamentary remnant radio emission and duty cycle constraints in the radio galaxy NGC 6086
• Feedback from low-to-moderate luminosity radio-AGN with MaNGA
• Connecting the radio AGN life cycle to feedback: Ionised gas is more disturbed in young radio AGN
• Core prominence as a signature of restarted jet activity in the LOFAR radio-galaxy population
• Jet-driven shocks and turbulence in radio-loud Active Galactic Nuclei observed with JWST MIRI/MRS
• Mapping the emission and spectral properties of the FRI radio galaxy 3C 449 with LOFAR and the VLA
• Combining LOFAR and Apertif Data for Understanding the Life Cycle of Radio Galaxies