The LOFAR view of giant, early-type galaxies: radio emission from active nuclei and star formation

Abstract

We study the properties and the origin of the radio emission in the most luminous early-type galaxies (ETGs) in the nearby Universe (MK<-25, recession velocity < 7,500 km/s) as seen by the 150 MHz Low-Frequency ARray (LOFAR) observations. LOFAR images are available for 188 of these giant ETGs (gETGs) and 146 (78%) of them are detected above a typical luminosity of ~10E21 W/Hz. They show a large spread in power, reaching up to ~10E26 W/Hz. We confirm a positive link between the stellar luminosity of gETGs and their median radio power, the detection rate, and the fraction of extended sources. About two-thirds (91) of the detected gETGs are unresolved, with sizes <4 kpc, confirming the prevalence of compact radio sources in local sources. Forty-six gETGs show extended emission on scales ranging from 4 to 340 kpc, at least 80% of which have a FRI class morphology. Based on the morphology and spectral index of the extended sources, ~30% of them might be remnant or restarted sources but further studies are needed to confirm this. Optical spectroscopy (available for 44 gETGs) indicates that for seven of them the nuclear gas is ionized by young stars suggesting a contribution to their radio emission from star forming regions. Their radio luminosities correspond to a star formation rate (SFR) in the range 0.1-8 Msun/yr and a median specific SFR of 0.8x10E-12 yr-1. The gas flowing toward the center of gETGs can accrete onto the supermassive black hole but also stall at larger radii and form new stars, an indication that feedback does not completely quench star formation. The most luminous gETGs (25 galaxies with MK < -25.8) are all detected at 150 MHz however they are not all currently turned on: at least four of them are remnant sources and at least one is likely powered by star formation.

Pre-proofs version - Accepted for publication in A&A

References in corpus (23)

• The Host Galaxies and Classification of Active Galactic Nuclei
• The LOFAR Two-metre Sky Survey - I. Survey Description and Preliminary Data Release
• UV-extended E-MILES stellar population models: young components in massive early-type galaxies
• Radio sources in the 6dFGS: Local luminosity functions at 1.4 GHz for star-forming galaxies and radio-loud AGN
• The Last of FIRST: The Final Catalog and Source Identifications
• The LOFAR Two Meter Sky Survey: Deep Fields, I -- Direction-dependent calibration and imaging
• Signals from the Noise: Image Stacking for Quasars in the FIRST Survey
• LOFAR/H-ATLAS: The low-frequency radio luminosity - star-formation rate relation
• LOFAR/H-ATLAS: A deep low-frequency survey of the Herschel-ATLAS North Galactic Pole field
• The duty cycle of local radio galaxies
• FR0CAT: a FIRST catalog of FR0 radio galaxies
• Search and modelling of remnant radio galaxies in the LOFAR Lockman Hole field
• Remnant radio-loud AGN in the Herschel-ATLAS field
• The life cycle of radio galaxies in the LOFAR Lockman Hole field
• A snapshot of the oldest AGN feedback phases
• Sub one percent mass fractions of young stars in red massive galaxies
• Remnant Radio Galaxies Discovered in a Multi-frequency Survey
• The LOFAR view of FR0 radio galaxies
• The best of both worlds: Combining LOFAR and Apertif to derive resolved radio spectral index images
• VLA Radio Study of a Sample of Nearby X-ray and Optically Bright Early-Type Galaxies
• Multi-frequency characterisation of remnant radio galaxies in the Lockman Hole field
• Parsec-scale Properties of eight Fanaroff-Riley Type 0 Radio Galaxies
• Radio Source Evolution on Galactic Scales

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• Core prominence as a signature of restarted jet activity in the LOFAR radio-galaxy population
• What Drives the Bimodal Distribution of Eddington-Scaled Radio Luminosity in Nearby Early-Type Galaxies?
• Infrared Spectroscopy of Nearby Radio Active Early-Type Galaxies -- II: Spectral Atlas
• MIGHTEE: The dark matter haloes, duty cycle and mechanical feedback from radio-AGN up to $z\sim 2.5$
• Hosts and environments: a (large-scale) radio history of AGN and star-forming galaxies
• Implications of the continuous radio-loudness distribution among AGNs in the local Universe
• The Optical Properties of Host Galaxies of Radio Sources in the Coma Cluster
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