The MIni-Halos in MIni-Clusters (MIMIC) project: New insights into the origin of mini-halos from a LOFAR, uGMRT, and MeerKAT study of diffuse radio emission in Abell 496 and ZwCl 235
Abstract
We aim at investigating the presence of diffuse radio emission in low-mass (M500≤3×1014 M⊙), relaxed galaxy clusters. We present a pilot study for the MIMIC (MIni-halos in MIni-Clusters) project, focusing on Abell 496 and ZwCl 235, using LOFAR (54, 144 MHz), uGMRT (400, 650 MHz), and MeerKAT (1.28 GHz) data, as well as Chandra X-ray data. We detect diffuse radio emission in the central 100 kpc of both Abell 496 and ZwCl 235, spatially confined within sloshing-induced cold fronts seen in X-ray images. The diffuse sources satisfy the classification criteria for radio mini-halos and represent the least powerful known to date, with 1.4 GHz radio powers of (2.2±0.2)×1022 W/Hz in Abell 496 and (1.3±0.3)×1022 W/Hz in ZwCl 235. The mini-halos have steep spectra (−1.9≤α≤−1.4), and in Abell 496 we find outward steepening of the spectral index. In both clusters, the radio and X-ray surface brightness are correlated over the diffuse source extent, with sub-linear or nearly linear slopes depending on frequency. Separately, we present the properties of two extended (>200 kpc) tailed radio galaxies in both clusters. The steep spectra, sub-linear radio-X-ray correlations, and confinement within cold fronts suggest that contribution from fossil plasma advected from the central radio galaxy and plausible turbulent re-acceleration are at play in Abell 496 and ZwCl 235. These two systems allow us to extend mini-halo scaling relations toward the low-power regime. We confirm a strong correlation between the mini-halo radio power and the cool core X-ray luminosity, with P1.4 ∝ LX,701.5±0.2. We find, for the first time, tentative indications that mini-halos with steeper radio spectra may preferentially be associated with lower core X-ray luminosities and lower radio power. (abridged)
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BibTeX
@misc{ubertosi2026minihalos,
title = {{The MIni-Halos in MIni-Clusters (MIMIC) project: New insights into the origin of mini-halos from a LOFAR, uGMRT, and MeerKAT study of diffuse radio emission in Abell 496 and ZwCl 235}},
author = {F. Ubertosi and S. Giacintucci and A. Botteon and A. Bonafede and T. Pasini and M. Balboni and N. Biava and G. Brunetti and T. Clarke and V. Cuciti and F. de Gasperin and P. Domínguez-Fernández and H. Edler and F. Gastaldello and M. Gitti and K. Kolokythas and G. V. Pignataro and C. J. Riseley and R. J. van Weeren and T. Venturi and J. Zuhone},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.28756},
eprint = {2610.28756},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.28756},
}
RIS
TY - UNPB
TI - The MIni-Halos in MIni-Clusters (MIMIC) project: New insights into the origin of mini-halos from a LOFAR, uGMRT, and MeerKAT study of diffuse radio emission in Abell 496 and ZwCl 235
AU - F. Ubertosi
AU - S. Giacintucci
AU - A. Botteon
AU - A. Bonafede
AU - T. Pasini
AU - M. Balboni
AU - N. Biava
AU - G. Brunetti
AU - T. Clarke
AU - V. Cuciti
AU - F. de Gasperin
AU - P. Domínguez-Fernández
AU - H. Edler
AU - F. Gastaldello
AU - M. Gitti
AU - K. Kolokythas
AU - G. V. Pignataro
AU - C. J. Riseley
AU - R. J. van Weeren
AU - T. Venturi
AU - J. Zuhone
PY - 2026
DA - 2026/10/20
PB - arXiv
DO - 10.48550/arxiv.2610.28756
UR - https://arxiv.org/abs/2610.28756
AB - We aim at investigating the presence of diffuse radio emission in low-mass (M_500≤3×10^14 M_⊙), relaxed galaxy clusters. We present a pilot study for the MIMIC (MIni-halos in MIni-Clusters) project, focusing on Abell 496 and ZwCl 235, using LOFAR (54, 144 MHz), uGMRT (400, 650 MHz), and MeerKAT (1.28 GHz) data, as well as Chandra X-ray data. We detect diffuse radio emission in the central 100 kpc of both Abell 496 and ZwCl 235, spatially confined within sloshing-induced cold fronts seen in X-ray images. The diffuse sources satisfy the classification criteria for radio mini-halos and represent the least powerful known to date, with 1.4 GHz radio powers of (2.2±0.2)×10^22 W/Hz in Abell 496 and (1.3±0.3)×10^22 W/Hz in ZwCl 235. The mini-halos have steep spectra (−1.9≤α≤−1.4), and in Abell 496 we find outward steepening of the spectral index. In both clusters, the radio and X-ray surface brightness are correlated over the diffuse source extent, with sub-linear or nearly linear slopes depending on frequency. Separately, we present the properties of two extended (>200 kpc) tailed radio galaxies in both clusters. The steep spectra, sub-linear radio-X-ray correlations, and confinement within cold fronts suggest that contribution from fossil plasma advected from the central radio galaxy and plausible turbulent re-acceleration are at play in Abell 496 and ZwCl 235. These two systems allow us to extend mini-halo scaling relations toward the low-power regime. We confirm a strong correlation between the mini-halo radio power and the cool core X-ray luminosity, with P_1.4 ∝ L_X,70^1.5±0.2. We find, for the first time, tentative indications that mini-halos with steeper radio spectra may preferentially be associated with lower core X-ray luminosities and lower radio power. (abridged)
ER -