A LOFAR-uGMRT spectral index study of distant radio halos - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Astronomy and Astrophysics - A&A Année : 2021

A LOFAR-uGMRT spectral index study of distant radio halos

G. Di Gennaro
  • Fonction : Auteur
R.J. van Weeren
  • Fonction : Auteur
R. Cassano
G. Brunetti
M. Brüggen
  • Fonction : Auteur
M. Hoeft
  • Fonction : Auteur
E. Osinga
  • Fonction : Auteur
A. Botteon
  • Fonction : Auteur
V. Cuciti
  • Fonction : Auteur
F. de Gasperin
H.J.A. Röttgering
  • Fonction : Auteur

Résumé

Context. Radio halos are megaparsec-scale diffuse radio sources mostly located at the centres of merging galaxy clusters. The common mechanism invoked to explain their origin is the re-acceleration of relativistic particles caused by large-scale turbulence.Aims. Current re-acceleration models predict that a significant number of halos at high redshift should be characterised by very steep spectra (α < −1.5) because of increasing inverse Compton energy losses. In this paper, we investigate the spectral index properties of a sample of nine clusters selected from the second Planck Sunyaev-Zel’dovich catalogue showing diffuse radio emission with the Low Frequency Array (LOFAR) in the 120–168 MHz band. This is the first time that radio halos discovered at low frequencies are followed up at higher frequencies.Methods. We analysed upgraded Giant Metrewave Radio Telescope (uGMRT) observations in Bands 3 and 4, that is, 250–500 and 550–900 MHz respectively. These observations were combined with existing LOFAR data to obtain information on the spectral properties of the diffuse radio emission.Results. We find diffuse radio emission in the uGMRT observations for five of the nine high-z radio halos previously discovered with LOFAR. For those, we measure spectral indices in the range of −1 to −1.4. For the uGMRT non-detections, we estimated that the halos should have a spectral index steeper than −1.5. We also confirm the presence of one candidate relic.Conclusions. Despite the small number of clusters, we find evidence that about half of the massive and merging clusters at high redshift host radio halos with a very steep spectrum. This is in line with theoretical predictions, although larger statistical samples are necessary to test models.Key words: radiation mechanisms: non-thermal / galaxies: clusters: general / galaxies: clusters: intracluster medium
Fichier principal
Vignette du fichier
aa41510-21.pdf (4.72 Mo) Télécharger le fichier
Origine : Fichiers éditeurs autorisés sur une archive ouverte

Dates et versions

hal-03339478 , version 1 (17-06-2022)

Identifiants

Citer

G. Di Gennaro, R.J. van Weeren, R. Cassano, G. Brunetti, M. Brüggen, et al.. A LOFAR-uGMRT spectral index study of distant radio halos. Astronomy and Astrophysics - A&A, 2021, 654, pp.A166. ⟨10.1051/0004-6361/202141510⟩. ⟨hal-03339478⟩
56 Consultations
15 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More