The best of both worlds: Combining LOFAR and Apertif to derive resolved radio spectral index images

Abstract

Supermassive black holes at the centres of galaxies can cycle through periods of activity and quiescence. Characterising the duty cycle of active galactic nuclei is crucial for understanding the impact of the energy they release on the host galaxy. For radio AGN, this can be done by identifying dying (remnant) and restarted radio galaxies from their radio spectral properties. Using the combination of images at 1400 MHz produced by Apertif, the new phased-array feed receiver installed on the Westerbork Synthesis Radio Telescope, and images at 150 MHz provided by LOFAR, we have derived resolved spectral index images (at a resolution of ~15 arcsec) for all the sources within ~6 deg^2 area of the Lockman Hole region. We were able to select 15 extended radio sources with emission (partly or entirely) characterised by extremely steep spectral indices (steeper than 1.2). These objects represent radio sources in the remnant or the restarted phases of their life cycle. Our findings suggest this cycle to be relatively fast. They also show a variety of properties relevant for modelling the evolution of radio galaxies. For example, the restarted activity can occur while the remnant structure from a previous phase of activity is still visible. This provides constraints on the duration of the 'off' (dying) phase. In extended remnants with ultra-steep spectra at low frequencies, the activity likely stopped a few hundred megayears ago, and they correspond to the older tail of the age distribution of radio galaxies, in agreement with simulations of radio source evolution. We find remnant radio sources with a variety of structures (from double-lobed to amorphous), suggesting different types of progenitors. The present work sets the stage for exploiting low-frequency spectral index studies of extended sources by taking advantage of the large areas common to the LOFAR and the Apertif surveys.

arXiv commentAccepted for publication in A&A. This paper is part of the 1st data release of the LoTSS Deep Fields. 17 pages, 10 figures

References in corpus (77)

• LOFAR: The LOw-Frequency ARray
• The Co-Evolution of Galaxies and Supermassive Black Holes: Insights from Surveys of the Contemporary Universe
• The GMRT 150 MHz All-sky Radio Survey: First Alternative Data Release TGSS ADR1
• Mechanical Feedback from Active Galactic Nuclei in Galaxies, Groups, and Clusters
• The LOFAR Two-metre Sky Survey - II. First data release
• GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey I: A low-frequency extragalactic catalogue
• Distant Radio Galaxies and their Environments
• A morphological algorithm for improving radio-frequency interference detection
• The cold gaseous halo of NGC 891
• Radio galaxies with a `double-double' morphology: I - Analysis of the radio properties and evidence for interrupted activity in active galactic nuclei
• Post-correlation radio frequency interference classification methods
• Radio galaxies and feedback from AGN jets
• Feedback from Central Black Holes in Elliptical Galaxies: Two-dimensional Models Compared to One-dimensional Models
• LOFAR 150-MHz observations of the Boötes field: Catalogue and Source Counts
• The LOFAR Two Meter Sky Survey: Deep Fields, I -- Direction-dependent calibration and imaging
• Feedback from central black holes in elliptical galaxies. III: models with both radiative and mechanical feedback
• Raining on black holes and massive galaxies: the top-down multiphase condensation model
• Revisiting the Fanaroff-Riley dichotomy and radio-galaxy morphology with the LOFAR Two-Metre Sky Survey (LoTSS)
• The LoTSS view of radio AGN in the local Universe. The most massive galaxies are always switched on
• Extragalactic Peaked-Spectrum Radio Sources at Low Frequencies
• A simulation-based analytic model of radio galaxies
• An XMM-Newton study of the environments, particle content and impact of low-power radio galaxies
• Simulations of supermassive black hole growth in high-redshift disk galaxies
• A radio spectral index map and catalogue at 147-1400 MHz covering 80 per cent of the sky
• In search of dying radio sources in the local universe
• The Energetics and Lifetimes of Local Radio Active Galactic Nuclei
• The LOFAR Two Metre Sky Survey: Deep Fields Data Release 1 -- III. Host-galaxy identifications and value added catalogues
• Feeding SMBHs through supersonic turbulence and ballistic accretion
• The Lockman Hole project: LOFAR observations and spectral index properties of low-frequency radio sources
• A search for distant radio galaxies from SUMSS and NVSS: III. radio spectral energy distributions and the z-alpha correlation
• The interstellar and circumnuclear medium of active nuclei traced by HI 21-cm absorption
• A representative survey of the dynamics and energetics of FRII radio galaxies
• Search and modelling of remnant radio galaxies in the LOFAR Lockman Hole field
• Cycling of the powerful AGN in MS 0735.6+7421 and the duty cycle of radio AGN in Clusters
• LOFAR discovery of an ultra-steep radio halo and giant head-tail radio galaxy in Abell 1132
• The LOFAR Two-metre Sky Survey IV. First Data Release: Photometric redshifts and rest-frame magnitudes
• A multiband study of Hercules A. II. Multifrequency VLA imaging
• LoTSS DR1: Double-double radio galaxies in the HETDEX field
• LOFAR discovery of a 700-kpc remnant radio galaxy at low redshift
• Remnant radio-loud AGN in the Herschel-ATLAS field
• The Lockman Hole Project: new constraints on the sub-mJy source counts from a wide-area 1.4 GHz mosaic
• 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
• Deep Low-Frequency Radio Observations of the NOAO Bootes Field: I. Data Reduction and Catalog Construction
• Radio properties of Compact Steep Spectrum and GHz-Peaked Spectrum radio sources
• ATLBS Extended Source Sample: The evolution in radio source morphology with flux density
• PKS 1814-637: a powerful radio-loud AGN in a disk galaxy
• The life cycle of radio galaxies in the LOFAR Lockman Hole field
• RAiSE II: resolved spectral evolution in radio AGN
• Recurrent radio emission and gas supply: the case of the radio galaxy B2 0258+35
• FR II radio galaxies at low frequencies I: morphology, magnetic field strength and energetics
• T-RaMiSu: The Two-meter Radio Mini Survey I. The Bootes Field
• Optical and radio properties of extragalactic radio sources with recurrent jet activity
• Episodic radio galaxies J0116$-$4722 and J1158+2621: can we constrain the quiescent phase of nuclear activity?
• Intermittent jet activity in the radio galaxy 4C29.30?
• On the population of remnant FRII radio galaxies and implications for radio source dynamics
• Radio Galaxy Zoo: Unsupervised Clustering of Convolutionally Auto-encoded Radio-astronomical Images
• LOFAR reveals the giant: a low-frequency radio continuum study of the outflow in the nearby FR I radio galaxy 3C 31
• Radiative age mapping of the remnant radio galaxy B2 0924+30: the LOFAR perspective
• Radio spectral properties and jet duty cycle in the restarted radio galaxy 3C388
• The flickering nuclear activity of Fornax A
• Serendipitous discovery of a dying Giant Radio Galaxy associated with NGC 1534, using the Murchison Widefield Array
• 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 peculiar radio galaxy 4C 35.06: a case for recurrent AGN activity?
• J021659-044920: a relic giant radio galaxy at z ~ 1.3
• LOFAR low-band antenna observations of the 3C295 and Bootes fields: source counts and ultra-steep spectrum sources
• Low-frequency study of two giant radio galaxies: 3C35 and 3C223
• Hard X-ray selected giant radio galaxies -- II. Morphological evidence of restarted radio activity
• Radio Galaxy Zoo: Knowledge Transfer Using Rotationally Invariant Self-Organising Maps
• A radio study of the double-double radio galaxy 3C293
• Investigating the cause of the $\alpha$-$z$ relation
• Numerical modelling of the lobes of radio galaxies in cluster environments -- IV. Remnant radio galaxies
• Radio spectra of bright compact sources at z>4.5
• The LOFAR Two Metre Sky Survey: Deep Fields. II. The ELAIS-N1 LOFAR deep field
• The diffuse radio emission around NGC 5580 and NGC 5588
• The LOFAR Two-metre Sky Survey Deep Fields -- Data Release 1: IV. Photometric redshifts and stellar masses
• RAiSE X: searching for radio galaxies in X-ray surveys

Cited by in corpus (19)

• The LOFAR Two-metre Sky Survey -- V. Second data release
• The wide-field, multiplexed, spectroscopic facility WEAVE: Survey design, overview, and simulated implementation
• The LOFAR LBA Sky Survey I. survey description and preliminary data release
• The LOFAR Two-metre Sky Survey Deep Fields Data Release 1: V. Survey description, source classifications and host galaxy properties
• AGN feeding and feedback in Fornax A: kinematical analysis of the multi-phase ISM
• First release of Apertif imaging survey data
• Ionised gas outflows over the radio AGN life cycle
• The LOFAR view of giant, early-type galaxies: radio emission from active nuclei and star formation
• Multi-frequency characterisation of remnant radio galaxies in the Lockman Hole field
• Unmasking the history of 3C 293 with LOFAR sub-arcsecond imaging
• The Dynamics and Energetics of Remnant and Restarting RLAGN
• Continuum source catalog for the first APERTIF data release
• The Apertif science verification campaign - Characteristics of polarised radio sources
• Finding AGN remnant candidates based on radio morphology with machine learning
• Connecting the radio AGN life cycle to feedback: Ionised gas is more disturbed in young radio AGN
• Apertif 1.4 GHz continuum observations of the Boötes field and their combined view with LOFAR
• Young but fading radio sources: searching for remnants among compact steep-spectrum radio sources
• Core prominence as a signature of restarted jet activity in the LOFAR radio-galaxy population
• Combining LOFAR and Apertif Data for Understanding the Life Cycle of Radio Galaxies