GRACE

Giant Radio galaxies and their duty cycle

Giants in the sky

The advent of new generation radio telescopes is opening new possibilities on the classification and study of extragalactic high-energy sources, specially the underrepresented ones like radio galaxies. Among these, Giant Radio Galaxies (GRG, larger than 0.7 Mpc) are among the most extreme manifestations of the accretion/ejection processes on supermassive black holes. Our recent studies have shown that GRG can be up to four times more abundant in hard X-ray selected (i.e. from INTEGRAL/IBIS and Swift/BAT at >20 keV) samples and, most interestingly, the majority of them present signs of restarted radio activity. This makes them the ideal testbed to study the so far unknown duty cycle of jets in active galactic nuclei. Open questions in the field include: How and when jets are restarted? How jets evolve and what’s their dynamic? What is the jet's duty cycle and what triggers them? Our group has recently collected a wealth of radio data on these high-energy selected GRGs, allowing us to study their jet formation and evolution from the pc to kpc scales, across different activity epochs. Furthermore, we are devoting an effort to the exploitation of new radio surveys data for the discovery of new classes of counterparts of Fermi/LAT and ANTARES catalogues. In particular, we are unveiling the hidden population of radio galaxies associated with gamma-ray sources, and with neutrino events.

The project is hosted by the GRAL group in Rome, and can count on international collaborators. In 2023, it has been funded through the ESA discovery programme. In this webpage, we collect the information on the GRG sample we are studying since 2016, providing reference works and highlights on our current results.

Team members

G. Bruni, F. Panessa, A. Bazzano, P. Ubertini (INAF-IAPS, Italy)
L. Bassani, F. Ursini, A. Malizia (INAF-OAS, Italy)
D. Dallacasa, T. Venturi, M. Brienza (INAF-IRA, Italy)
L. Hernandez-Garcia (U. Valparaiso, Chile)
L. Saripalli (Raman Research Institute, India)
F. Massaro (U. Torino, Italy)
M. Fanelli (U. Sapienza / INAF-IAPS, Italy)

The sample

Bassani et al. (2016) performed a combined radio/hard X-ray study of the active galactic nuclei (AGN) population selected in the hard X-ray band by the International Gamma-Ray Astrophysics Laboratory (INTEGRAL)/the Imager on Board the INTEGRAL Satellite (IBIS) and Swift/the Burst Alert Telescope (BAT) surveys, finding 64 objects that match radio galaxies with known redshifts. The NRAO Very Large Array (VLA) Sky Survey (NVSS) and Sydney University Molonglo Sky Survey (SUMSS) maps allowed an estimate of the projected linear size, and it turned out that 15 of them (i.e., ∼25% of the sample) can be classified as GRG. In the following, the GRG sample we are studying in detail since 2016. We recently added further objects, following the catalogue update by Bassani et al. (2020).

Name RA DEC z LS (kpc)

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B3 0309+411B 03:13:01.9 +41:20:01 0.134 1150

J0318+684 03:18:19.1 +68:29:32.2 0.09 1523

PKS 0707–35 07:09:13.8 -36:01:19.9 0.111 1016

4C 73.08 09:49:46.0 +73:14:23.1 0.058 936

B2 1144+35B 11:47:22.3 +35:01:09.1 0.06 1200

HE 1434–1600 14:36:49.6 -16:13:40.4 0.144 1823

IGR J14488–4008 14:48:50.98 -40:08:47.12 0.123 1540

4C +63.22 15:23:45.8 +63:39:24.8 0.204 709

Mrk 1498 16:28:03.8 +51:46:30.7 0.05 1204

4C +34.47 17:23:20.6 +34:18:00.3 0.206 817

IGR J17488–2338 17:48:38.9 -23:35:26.8 0.24 1415

PKS 2014–55 20:18:01.0 -55:39:28.8 0.06 1484

4C +74.26 20:42:36.7 +75:08:02.7 0.104 1211

PKS 2331–240 23:33:55.25 -23:43:41.76 0.048 1174

PKS 2356–61 23:59:03.9 -60:54:59.7 0.096 718

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Recently added objects from Bassani et al. (2020)

Name RA DEC z LS (kpc)

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SWIFT J0225.8+5946 02:26:26.15 +59:27:53.0 - -

SWIFT J0632.1-5404 06:32:00.95 -54:04:55.89 0.20 1003

SWIFT J0636.5-20368 06:36:32.16 -20:34:53.35 0.05 950

SWIFT J0801.7+4764 08:01:31.96 +47:36:16.06 0.16 970

SWIFT J1153.9+5848 11:53:23.927 +58:31:38.501 0.20 840

SWIFT J1238.4+5349 12:38:07.77 +53:25:55.90 0.35 780

IGR J13107–5626 13:10:36.90 -56 26 56.31 0.09 710

SWIFT J1503.7+6850 15:04:13.10 +68:56:10.5 0.32 870

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Results Highlights

Through a joint morphological and spectral radio analysis, we could verify that the majority of our sources present a restarted radio phase (Bruni+2019, 2020)

In particular, we found that 8 sources present a GigaHertz Peaked Spectrum in the radio band, suggesting the presence of a new, compact radio phase in their core.

The morphological analysis of the extended lobes, carried out with both surveys (LoTSS, TGSS) and proprietary data (ATCA, uGMRT), allowed us to spot cases of X-shaped, Cocoon, and Double-Double sources (Bruni+2020, 2021)

In the following, a collection of images in the MHz domain from Bruni+2020

A follow-up of the entire sample at milli-arcsec resolution, through an EVN+LBA large program, was performed in 2021, and results are under analysis. Zooming into the core of these giants, we will be able to estimate the age of the newborn jet, and the overall duty cyle of the radio phase. An additional goal is to look for precessing jets, possibly hinting a binary black hole system. As an added value, the latter goal would be a preparatory study for the next generation of gravitational waves antennas (E.T., LISA), that will cover the low frequency domain dominated by B-SMBH.

Finally, through a synchrotron ageing analysis we are establishing the age of the plasma forming the extended lobes, revealing their Myr-long history. So far, we have collected data for a pilot sample of three sources, to be expanded thanks to recent radio surveys with SKA precursors as MeerKAT+ and ASKAP.

On the right: spectral age in Myr, age error, and chi^2 for lobe A of source B2 1144+35B, for different values of the magnetic field (Fanelli 2024, Master Thesis).

The tip of the iceberg: an emerging population of high-energy radio galaxies

New radio surveys are unveiling a growing population of radio galaxies associated with gamma-ray sources (GeV-RG), in contrast with the common picture that sees blazar as the almost unique counterpart. Our group has recently studied a peculiar Fanaroff- Riley II INTEGRAL radio galaxy with a counterpart in the Fermi/LAT catalogue. Through a broad-band spectral fitting from radio to gamma-ray, we found that the commonly invoked jet contribution is not sufficient to account for the observed gamma-ray flux. Instead, our modelling suggested that the observed emission could mainly originate in the lobes (rather than in the radio core) by inverse Compton scattering of radio-emitting electrons off the ambient photon fields.

As a follow-up of this work, we have proposed to join the MeerKAT+ survey (starting in 2024) through the recent INAF partnership, with the goal of identifying Fermi radio galaxy counterparts in the Southern hemisphere.

Papers

IGR J18249-3243: a new GeV-emitting FR II and the emerging population of high-energy radio galaxies, G. Bruni, L. Bassani, M. Persic et al. 2022, MNRAS 513, 886
Hard X-ray selected giant radio galaxies – III. The LOFAR view, G. Bruni, M. Brienza, F. Panessa et al. 2021, MNRAS 503, 4681
Soft gamma-ray selected giant radio galaxies: an update, L. Bassani, F. Ursini, A. Malizia et al. 2020, MNRAS 500, 3111
Hard X-ray selected giant radio galaxies – II. Morphological evidence of restarted radio activity, G. Bruni, F. Panessa, L. Bassani et al. 2020, MNRAS 494, 902
A young and obscured AGN embedded in the giant radio galaxy Mrk 1498, L. Hernandez-Garcia, F. Panessa, L. Bassani, MNRAS, 489, 4049
A Discovery of Young Radio Sources in the Cores of Giant Radio Galaxies Selected at Hard X-Rays, G. Bruni, F. Panessa, L. Bassani et al. 2019, ApJL 875, 88
Hard X-ray-selected giant radio galaxies - I. The X-ray properties and radio connection, F. Ursini, L. Bassani, F. Panessa et al. 2018, MNRAS, 481, 4250
Variable broad lines and outflow in the weak blazar PBC J2333.9-2343, L. Hernandez-Garcia, G. Vietri, F. Panessa, MNRAS, 478, 4634
Restarting activity in the nucleus of PBC J2333.9-2343. An extreme case of jet realignment, L. Hernandez-Garcia, F. Panessa, M. Giroletti et al. 2017, A&A, 603, A131
Soft γ-ray selected radio galaxies: favouring giant size discovery, L. Bassani, T. Venturi, M. Molina et al. 2016, MNRAS, 461, 3165

Slides & videos

GRACE Project summary, video prepared for COSPAR 2020
Seminar at INAF-IAPS, video recorded on 08/11/2023
The GRACE project: high energy radio galaxies and their duty cycle, G. Bruni, COSPAR General Assembly, Busan 13-21 July 2024
A high fraction of restarting sources in soft gamma-ray selected giant radio galaxies, G. Bruni, 12th INTEGRAL conference, Geneva 11-15 February 2019
High-energy view of hard X-ray selected radio galaxies, F. Ursini, 12th INTEGRAL conference, Geneva 11-15 February 2019

Theses

Duty cycle and synchrotron ageing of giant radio galaxies, Matteo Fanelli, Master Degree, Sapienza University (Rome)

Outreach

La storia delle radiogalassie scritta nei getti radio, Media INAF, March 2021
La popolazione emergente di radiogalassie nel cielo gamma di INTEGRAL e Fermi, ASI News, May 2022