LOFAR discovery of a double radio halo system in Abell 1758 and radio/X-ray study of the cluster pair

Context. Diffuse radio emission associated with the intracluster medium (ICM) is observed in a number of merging galaxy clusters. It is currently believed that a fraction of the kinetic energy in mergers is channeled into nonthermal components, such as turbulence, cosmic rays, and magnetic fields, which may lead to the formation of giant synchrotron sources in the ICM. Aims. Studying merging galaxy clusters in different evolutionary phases is fundamental for understanding the origin of radio emission in the ICM. Methods. We observed the nearby galaxy cluster pair RXC J1825.3+3026 (z ∼ 0.065) and CIZA J1824.1+3029 (z ∼ 0.071) at 120 − 168 MHz with the LOw Frequency ARray (LOFAR) and made use of a deep (240 ks) XMM-Newton dataset to study the nonthermal and thermal properties of the system. RXC J1825.3+3026 is in a complex dynamical state, with a primary ongoing merger in the E-W direction and a secondary later stage merger with a group of galaxies in the SW, while CIZA J1824.1+3029 is dynamically relaxed. These two clusters are in a pre-merger phase. Results. We report the discovery of a Mpc-scale radio halo with a low surface brightness extension in RXC J1825.3+3026 that follows the X-ray emission from the cluster center to the remnant of a galaxy group in the SW. This is among the least massive systems and the faintest giant radio halo known to date. In contrast to this, no diffuse radio emission is observed in CIZA J1824.1+3029, nor in the region between the pre-merger cluster pair. The power spectra of the X-ray surface brightness fluctuations of RXC J1825.3+3026 and CIZA J1824.1+3029 are in agreement with the findings for clusters exhibiting a radio halo and clusters where no radio emission has been detected, respectively. Conclusions. We provide quantitative support to the idea that cluster mergers play a crucial role in the generation of nonthermal components in the ICM.

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Radio and X-ray observations of the radio halo source in A1367

The Astrophysical Journal ◽

10.1086/161134 ◽

1983 ◽

Vol 270 ◽

pp. 410 ◽

Cited By ~ 12

Author(s):

G. Gavazzi ◽

G. Trinchieri

Keyword(s):

X Ray ◽

Radio Halo

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Suzaku Observation of the Radio Halo Cluster Abell 2319: Gas Dynamics and Hard X-Ray Properties

Publications of the Astronomical Society of Japan ◽

10.1093/pasj/61.6.1293 ◽

2009 ◽

Vol 61 (6) ◽

pp. 1293-1303 ◽

Cited By ~ 23

Author(s):

Chika Sugawara ◽

Motokazu Takizawa ◽

Kazuhiro Nakazawa

Keyword(s):

Gas Dynamics ◽

X Ray ◽

Radio Halo

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Chandrameasurements of non-thermal-like X-ray emission from massive, merging, radio halo clusters

Monthly Notices of the Royal Astronomical Society ◽

10.1111/j.1365-2966.2009.15359.x ◽

2009 ◽

Vol 399 (3) ◽

pp. 1307-1327 ◽

Cited By ~ 37

Author(s):

E. T. Million ◽

S. W. Allen

Keyword(s):

X Ray ◽

Radio Halo

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ClG 0217+70: A massive merging galaxy cluster with a large radio halo and relics

Astronomy and Astrophysics ◽

10.1051/0004-6361/202039028 ◽

2020 ◽

Vol 642 ◽

pp. L3

Author(s):

X. Zhang ◽

A. Simionescu ◽

J. S. Kaastra ◽

H. Akamatsu ◽

D. N. Hoang ◽

...

Keyword(s):

Surface Brightness ◽

Galaxy Cluster ◽

Precise Determination ◽

Optical Data ◽

Scaling Relations ◽

Thermal Pressure ◽

X Ray ◽

Radio Halo ◽

Physical Scale

We present an analysis of archival Chandra data of the merging galaxy cluster ClG 0217+70. The Fe XXV Heα X-ray emission line is clearly visible in the 25 ks observation, allowing a precise determination of the redshift of the cluster as z = 0.180 ± 0.006. We measure kT500 = 8.3 ± 0.4 keV and estimate M500 = (1.06 ± 0.11) × 1015 M⊙ based on existing scaling relations. Correcting both the radio and X-ray luminosities with the revised redshift reported here, which is much larger than previously inferred based on sparse optical data, this object is no longer an X-ray underluminous outlier in the LX − Pradio scaling relation. The new redshift also means that, in terms of physical scale, ClG 0217+70 hosts one of the largest radio halos and one of the largest radio relics known to date. Most of the relic candidates lie in projection beyond r200. The X-ray morphological parameters suggest that the intracluster medium is still dynamically disturbed. Two X-ray surface brightness discontinuities are confirmed in the northern and southern parts of the cluster, with density jumps of 1.40 ± 0.16 and 3.0 ± 0.6, respectively. We also find a 700 × 200 kpc X-ray faint channel in the western part of the cluster, which may correspond to compressed heated gas or increased non-thermal pressure due to turbulence or magnetic fields.

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A radio halo surrounding the Brightest Cluster Galaxy in RXCJ0232.2–4420: a mini-halo in transition?

Monthly Notices of the Royal Astronomical Society Letters ◽

10.1093/mnrasl/slz061 ◽

2019 ◽

Vol 486 (1) ◽

pp. L80-L84 ◽

Cited By ~ 3

Author(s):

Ruta Kale ◽

Krishna M Shende ◽

Viral Parekh

Keyword(s):

Radio Source ◽

Surface Brightness ◽

Galaxy Cluster ◽

Cosmic Ray ◽

Radio Sources ◽

Cluster Galaxy ◽

X Ray ◽

Radio Halo ◽

The Galaxy ◽

Radio Power

ABSTRACT Diffuse radio sources associated with the intra-cluster medium are direct probes of the cosmic ray electrons and magnetic fields. We report the discovery of a diffuse radio source in the galaxy cluster RXCJ0232.2–4420 (SPT-CL J0232–4421, z = 0.2836) using 606 MHz observations with the Giant Metrewave Radio Telescope. The diffuse radio source surrounds the Brightest Cluster Galaxy in the cluster-like typical radio mini-haloes. However the total extent of it is 550 × 800 kpc2, which is larger than mini-haloes and similar to that of radio haloes. The BCG itself is also a radio source with a marginally resolved core at 7 arcsec (30 kpc) resolution. We measure the 606 MHz flux density of the RH to be 52 ± 5 mJy. Assuming a spectral index of 1.3, the 1.4 GHz radio power is 4.5 × 1024 W Hz−1. The dynamical state of the cluster has been inferred to be 'relaxed’ and also as 'complex’, depending on the classification methods based on the morphology of the X-ray surface brightness. This system thus seems to be in the transition phase from a mini-halo to a radio halo.

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A giant radio bridge connecting two clusters in Abell 1758

Monthly Notices of the Royal Astronomical Society Letters ◽

10.1093/mnrasl/slaa142 ◽

2020 ◽

Author(s):

A Botteon ◽

R J van Weeren ◽

G Brunetti ◽

F de Gasperin ◽

H T Intema ◽

...

Keyword(s):

Radio Emission ◽

Galaxy Clusters ◽

Large Scale ◽

Synchrotron Emission ◽

X Ray ◽

Compressed Gas ◽

Order Of Magnitude ◽

Thermal Phenomena ◽

Cluster Pair ◽

Radio Halos

Abstract Collisions between galaxy clusters dissipate enormous amounts of energy in the intra-cluster medium (ICM) through turbulence and shocks. In the process, Mpc-scale diffuse synchrotron emission in form of radio halos and relics can form. However, little is known about the very early phase of the collision. We used deep radio observations from 53 MHz to 1.5 GHz to study the pre-merging galaxy clusters A1758N and A1758S that are ∼2 Mpc apart. We confirm the presence of a giant bridge of radio emission connecting the two systems that was reported only tentatively in our earlier work. This is the second large-scale radio bridge observed to date in a cluster pair. The bridge is clearly visible in the LOFAR image at 144 MHz and tentatively detected at 53 MHz. Its mean radio emissivity is more than one order of magnitude lower than that of the radio halos in A1758N and A1758S. Interestingly, the radio and X-ray emissions of the bridge are correlated. Our results indicate that non-thermal phenomena in the ICM can be generated also in the region of compressed gas in-between infalling systems.

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