J1248+4826: A diffuse radio source consistent with re-energized fossil plasma in a galaxy group
Abstract
High-resolution, sub-gigahertz radio surveys have revealed a growing number of diverse, diffuse radio sources, presenting new challenges in classifying them and deciphering their nature. We report the discovery of J1248+4826, a complex diffuse radio source in the Low Frequency Array (LOFAR) Two Metre Sky Survey and investigate its physical origin. We analyzed the radio morphology and spectrum of J1248+4826 and studied its environment and optical counterparts using multiwavelength data. After subtracting the radio emission of the bright radio galaxies in the field to isolate the diffuse component, we compared it with known diffuse radio sources including odd radio circles (ORCs), diffuse circular sources, cluster halos, and remnant lobes to establish its nature and formation mechanism. The apparent ring-like morphology, high radio luminosity, and steep spectrum of J1248+4826 initially suggested that this source might be a new ORC or a diffuse circular source. However, the residual radio emission reveals a compact (~30 kpc radius) horseshoe-shaped inner structure, embedded in an extended (~200 kpc) diffuse envelope, with an ultra-steep spectrum (alpha=1.7+/-0.2), which we interpret as a re-energized remnant lobe. The analysis of the multiwavelength data reveals a possible association with a galaxy group at z=0.2 and points to its most massive known member, a currently inactive early type galaxy located ~55 kpc from the structure's center, as the progenitor. Moderate shocks associated with the group dynamics provide a plausible reacceleration mechanism, although the details of such a process remain uncertain with the current data. J1248+4826 highlights the increasing diversity of diffuse radio phenomena and the challenges in their study and classification, while also revealing their potential to study the interplay between galaxies and their environment on large scales.
Versions
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BibTeX
@misc{polletta2026j12484826,
title = {{J1248+4826: A diffuse radio source consistent with re-energized fossil plasma in a galaxy group}},
author = {M. Polletta and A. L. Coil and B. L. Frye and H. Dole},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2605.05174},
eprint = {2605.05174},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2605.05174},
}
RIS
TY - UNPB
TI - J1248+4826: A diffuse radio source consistent with re-energized fossil plasma in a galaxy group
AU - M. Polletta
AU - A. L. Coil
AU - B. L. Frye
AU - H. Dole
PY - 2026
DA - 2026/09/14
PB - arXiv
DO - 10.48550/arxiv.2605.05174
UR - https://arxiv.org/abs/2605.05174
AB - High-resolution, sub-gigahertz radio surveys have revealed a growing number of diverse, diffuse radio sources, presenting new challenges in classifying them and deciphering their nature. We report the discovery of J1248+4826, a complex diffuse radio source in the Low Frequency Array (LOFAR) Two Metre Sky Survey and investigate its physical origin. We analyzed the radio morphology and spectrum of J1248+4826 and studied its environment and optical counterparts using multiwavelength data. After subtracting the radio emission of the bright radio galaxies in the field to isolate the diffuse component, we compared it with known diffuse radio sources including odd radio circles (ORCs), diffuse circular sources, cluster halos, and remnant lobes to establish its nature and formation mechanism. The apparent ring-like morphology, high radio luminosity, and steep spectrum of J1248+4826 initially suggested that this source might be a new ORC or a diffuse circular source. However, the residual radio emission reveals a compact (~30 kpc radius) horseshoe-shaped inner structure, embedded in an extended (~200 kpc) diffuse envelope, with an ultra-steep spectrum (alpha=1.7+/-0.2), which we interpret as a re-energized remnant lobe. The analysis of the multiwavelength data reveals a possible association with a galaxy group at z=0.2 and points to its most massive known member, a currently inactive early type galaxy located ~55 kpc from the structure's center, as the progenitor. Moderate shocks associated with the group dynamics provide a plausible reacceleration mechanism, although the details of such a process remain uncertain with the current data. J1248+4826 highlights the increasing diversity of diffuse radio phenomena and the challenges in their study and classification, while also revealing their potential to study the interplay between galaxies and their environment on large scales.
ER -