<i>XMM-NEWTON</i>OBSERVATION OF THE NORTHWEST RADIO RELIC REGION IN A3667

Finoguenov, A.; Sarazin, Craig L.; Nakazawa, K.; Wik, Daniel R.; Clarke, T. E.

doi:10.1088/0004-637x/715/2/1143

Cited by 159 publications

(254 citation statements)

References 33 publications

(40 reference statements)

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“…For an average integrated spectral index of −0.9 ± 0.1, we find a lower Mach number of 2.4 ± 0.1 for both the NW and SE relics. The Mach number at the NW shock front inferred from X-ray observations is 2.4 ± 0.8 over a region that encompasses most of the NW relic (Finoguenov et al 2010). This is in good agreement with our average value of the Mach number but significantly lower than our leading edge value.…”

Section: Radio Relics In A3667supporting

confidence: 90%

“…Many authors propose that this elongation coupled with the high velocity dispersion of cluster members (∼1200 km s −1 ) is an indication of a recent or ongoing merger between two subclusters in the plane of the sky. Numerous X-ray observations of A3667 (Ebeling et al 1996;Knopp, Henry & Briel 1996;Markevitch, Sarazin & Vikhlinin 1999;Vikhlinin, Markevitch & Murray 2001;Finoguenov et al 2010;Sarazin, Finoguenov & Wik 2013) have probed the physical properties of the hot gas that exists within the ICM of A3667. The cluster is found to have an X-ray luminosity of L x = 9 × 10 44 ergs s −1 in the 0.1-2.4 keV range (Ebeling et al 1996) with a temperature profile that is also elongated in the SE to NW direction and shows a sharp change in temperature at the NW periphery of the cluster.…”

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confidence: 99%

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The First Murchison Widefield Array low-frequency radio observations of cluster scale non-thermal emission: the case of Abell 3667

Hindson¹,

Johnston‐Hollitt²,

Hurley‐Walker³

et al. 2014

Monthly Notices of the Royal Astronomical Society

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We present the first Murchison Widefield Array observations of the well-known cluster of galaxies Abell 3667 (A3667) between 105 and 241 MHz. A3667 is one of the best known examples of a galaxy cluster hosting a double radio relic and has been reported to contain a faint radio halo and bridge. The origin of radio haloes, relics and bridges is still unclear, however galaxy cluster merger seems to be an important factor. We clearly detect the north-west (NW) and south-east radio relics in A3667 and find an integrated flux density at 149 MHz of 28.1 ± 1.7 and 2.4 ± 0.1 Jy, respectively, with an average spectral index, between 120 and 1400 MHz, of −0.9 ± 0.1 for both relics. We find evidence of a spatial variation in the spectral index across the NW relic steepening towards the centre of the cluster, which indicates an ageing electron population. These properties are consistent with higher frequency observations. We detect emission that could be associated with a radio halo and bridge. However, due to the presence of poorly sampled large-scale Galactic emission and blended point sources we are unable to verify the exact nature of these features.

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Section: Radio Relics In A3667supporting

confidence: 90%

mentioning

confidence: 99%

The First Murchison Widefield Array low-frequency radio observations of cluster scale non-thermal emission: the case of Abell 3667

Hindson¹,

Johnston‐Hollitt²,

Hurley‐Walker³

et al. 2014

Monthly Notices of the Royal Astronomical Society

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“…Follow-up X-ray observations of the northwest radio relic in Abell 3667 revealed that the ICM temperature and surface brightness distribution drops across the relic, which indicates the existence of a shock front across the relic (Finoguenov et al 2010). The correspondence between radio relics and shocks is also confirmed in other clusters (Macario et al 2011;Akamatsu et al 2012aAkamatsu et al ,b, 2013Bourdin et al 2013).…”

Section: Introductionmentioning

confidence: 68%

SuzakuX-ray study of the double radio relic galaxy cluster CIZA J2242.8+5301

Akamatsu

Weeren

Ogrean

et al. 2015

A&A

105

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Context. We present the results from Suzaku observations of the merging cluster of galaxies CIZA J2242.8+5301 at z = 0.192. Aims. To study the physics of gas heating and particle acceleration in cluster mergers, we investigated the X-ray emission from CIZA J2242.8+5301, which hosts two giant radio relics in the northern and southern part of the cluster. Methods. We analyzed data from three-pointed Suzaku observations of CIZA J2242.8+5301 to derive the temperature distribution in four different directions. Results. The intracluster medium (ICM) temperature shows a remarkable drop from 8.5 +0.8 −0.6 keV to 2.7 +0.7 −0.4 keV across the northern radio relic. The temperature drop is consistent with a Mach number M n = 2.7 +0.7 −0.4 and a shock velocity v shock:n = 2300 +700 −400 km s −1 . We also confirm the temperature drop across the southern radio relic. However, the ICM temperature beyond this relic is much higher than beyond the northern relic, which gives a Mach number M s = 1.7 +0.4 −0.3 and shock velocity v shock:s = 2040 +550 −410 km s −1 . These results agree with other systems showing a relationship between the radio relics and shock fronts which are induced by merging activity. We compare the X-ray derived Mach numbers with the radio derived Mach numbers from the radio spectral index under the assumption of diffusive shock acceleration in the linear test particle regime. For the northern radio relic, the Mach numbers derived from X-ray and radio observations agree with each other. Based on the shock velocities, we estimate that CIZA J2242.8+5301 is observed approximately 0.6 Gyr after core passage. The magnetic field pressure at the northern relic is estimated to be 9% of the thermal pressure.

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“…There is a considerable amount of evidence that radio relics trace shock fronts where particles are being (re-)accelerated, as was proposed initially in Enßlin et al (1998). The key observational facts that support the shock-radio relic connection are (i) the high polarization of some relics, with the apparent magnetic field lines being parallel to the major axis of the relics (e.g., van Weeren et al 2010;Bonafede et al 2012;Kale et al 2012;de Gasperin et al 2014), indicating that the ICM and associated magnetic fields are compressed, (ii) the presence of spectral index gradients, indicating electron cooling in the post-shock region of an outward traveling shock wave (e.g., Giacintucci et al 2008;van Weeren et al 2010van Weeren et al , 2011Stroe et al 2013;Hindson et al 2014), (iii) a change from power-law radio spectra at the outer edge of relics toward curved spectra in the post-shock region, indicating a site of acceleration and electron cooling (van Weeren et al 2012a;Stroe et al 2013), and (iv) the presence of ICM density and/or temperature jumps at the location of relics (e.g., Finoguenov et al 2010;Macario et al 2011;Akamatsu & Kawahara 2013;Bourdin et al 2013;Ogrean et al 2014a). X-ray observations indicate that the shock Mach numbers () are low, typically 3  .…”

Section: Introductionmentioning

confidence: 99%

Lofar, Vla, and Chandra Observations of the Toothbrush Galaxy Cluster

Weeren

Brunetti

Brüggen

et al. 2016

ApJ

154

212

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We present deep LOFAR observations between 120 and 181 MHz of the "Toothbrush" (RX J0603.3+4214), a cluster that contains one of the brightest radio relic sources known. Our LOFAR observations exploit a new and novel calibration scheme to probe 10 times deeper than any previous study in this relatively unexplored part of the spectrum. The LOFAR observations, when combined with VLA, GMRT, and Chandra X-ray data, provide new information about the nature of cluster merger shocks and their role in re-accelerating relativistic particles. We derive a spectral index of 0.8 0.1 a = - at the northern edge of the main radio relic, steepening toward the south to 2 a » -. The spectral index of the radio halo is remarkably uniform ( 1.16 a = -, with an intrinsic scatter of 0.04  ). The observed radio relic spectral index gives a Mach number of 2.8 0.3 0.5  = -+ , assuming diffusive shock acceleration. However, the gas density jump at the northern edge of the large radio relic implies a much weaker shock ( 1.2  » , with an upper limit of 1.5  » ). The discrepancy between the Mach numbers calculated from the radio and X-rays can be explained if either (i) the relic traces a complex shock surface along the line of sight, or (ii) if the radio relic emission is produced by a re-accelerated population of fossil particles from a radio galaxy. Our results highlight the need for additional theoretical work and numerical simulations of particle acceleration and reacceleration at cluster merger shocks.

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XMM-NEWTONOBSERVATION OF THE NORTHWEST RADIO RELIC REGION IN A3667

Cited by 159 publications

References 33 publications

The First Murchison Widefield Array low-frequency radio observations of cluster scale non-thermal emission: the case of Abell 3667

The First Murchison Widefield Array low-frequency radio observations of cluster scale non-thermal emission: the case of Abell 3667

SuzakuX-ray study of the double radio relic galaxy cluster CIZA J2242.8+5301

Lofar, Vla, and Chandra Observations of the Toothbrush Galaxy Cluster

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