LOFAR Detection of a Low-Power Radio Halo in the Galaxy Cluster Abell 990

Abstract

Radio halos are extended ($\sim \mathrm{Mpc}$), steep-spectrum sources found in the central region of dynamically disturbed clusters of galaxies. Only a handful of radio halos have been reported to reside in galaxy clusters with a mass $M_{500}\lesssim 5\times 10^{14}{M}_{\odot }$. In this paper we present a LOFAR 144 MHz detection of a radio halo in the galaxy cluster Abell 990 with a mass of $M_{500}=(4.9\pm 0.3)\times 10^{14}{M}_{\odot }$. The halo has a projected size of $\sim$700$\mathrm{kpc}$ and a flux density of $20.2\pm 2.2\mathrm{mJy}$ or a radio power of $1.2\pm 0.1\times 10^{24}{\mathrm{W}\mathrm{Hz}}^{-1}$ at the cluster redshift ($z=0.144$) which makes it one of the two halos with the lowest radio power detected to date. Our analysis of the emission from the cluster with Chandra archival data using dynamical indicators shows that the cluster is not undergoing a major merger but is a slightly disturbed system with a mean temperature of $5\mathrm{keV}$. The low X-ray luminosity of $L_X=(3.66\pm 0.08)\times 10^{44}{\mathrm{ergs}\mathrm{s}}^{-1}$ in the 0.1--2.4 keV band implies that the cluster is one of the least luminous systems known to host a radio halo. Our detection of the radio halo in Abell 990 opens the possibility of detecting many more halos in poorly-explored less-massive clusters with low-frequency telescopes such as LOFAR, MWA (Phase II) and uGMRT.

References in corpus (21)

• HI4PI: A full-sky HI survey based on EBHIS and GASS
• WSClean: an implementation of a fast, generic wide-field imager for radio astronomy
• The LOFAR Two-metre Sky Survey - I. Survey Description and Preliminary Data Release
• Diffuse Radio Emission from Galaxy Clusters
• Compressible Turbulence in Galaxy Clusters: Physics and Stochastic Particle Re-acceleration
• On the connection between giant radio halos and cluster mergers
• The impact of mergers on relaxed X-ray clusters - I. Dynamical evolution and emergent transient structures
• A low-frequency radio halo associated with a cluster of galaxies
• Searching for Cool Core Clusters at High redshift
• Radio interferometric gain calibration as a complex optimization problem
• Statistics of Giant Radio Halos from Electron Reacceleration Models
• LOFAR/H-ATLAS: A deep low-frequency survey of the Herschel-ATLAS North Galactic Pole field
• Non-linear Kalman filters for calibration in radio interferometry
• Relativistic protons in the Coma galaxy cluster: first gamma-ray constraints ever on turbulent reacceleration
• A giant radio halo in the cool core cluster CL1821+643
• On the absence of radio halos in clusters with double relics
• Characterization of ICM Temperature Distributions of 62 Galaxy Clusters with XMM-Newton
• Compression of interferometric radio-astronomical data
• ATCA observations of the MACS-Planck Radio Halo Cluster Project - I. New detection of a radio halo in PLCK G285.0-23.7
• A Massive Cluster at z = 0.288 Caught in the Process of Formation: The Case of Abell 959
• The Galaxy Cluster 'Pypeline' for X-ray Temperature Maps: ClusterPyXT

Cited by in corpus (9)

• The Planck clusters in the LOFAR sky. I. LoTSS-DR2: new detections and sample overview
• Abell 1033: Radio halo and gently reenergized tail at 54 MHz
• Nonthermal phenomena in the center of Abell 1775: An 800 kpc head-tail, revived fossil plasma and slingshot radio halo
• MERGHERS Pilot: MeerKAT discovery of diffuse emission in nine massive Sunyaev-Zel'dovich-selected galaxy clusters from ACT
• Discovery of a radio halo (and relic) in a $M_{500}<2\times 10^{14}$ M${}_{\odot }$ cluster
• Diffuse radio emission from non-Planck galaxy clusters in the LoTSS-DR2 fields
• Optical/X-ray/radio view of Abell 1213: A galaxy cluster with anomalous diffuse radio emission
• Combined LOFAR-uGMRT analysis of the diffuse radio emission in the massive clusters Abell 773 and Abell 1351
• A deep study of A399-401: An application for wide-field facet calibration