Standoff distance of bow shocks in galaxy clusters as proxy for Mach number

Zhang, Congyao; Churazov, E.; Forman, W.; Jones, Christine

doi:10.1093/mnras/sty2501

Cited by 33 publications

(25 citation statements)

References 23 publications

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“…Projection effects tend to underestimate M T and M ρ (e.g. Zhang et al 2019). On the other hand, the M T may also be biased high, if the pre-shock temperature is underestimated.…”

Section: Cfs and Merger Shocksmentioning

confidence: 99%

Chandra and XMM–Newton observations of A2256: cold fronts, merger shocks, and constraint on the IC emission

Liu

Sun

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We present the results of deep Chandra and XMM-Newton observations of a complex merging galaxy cluster Abell 2256 (A2256) that hosts a spectacular radio relic. The temperature and metallicity maps show clear evidence of a merger between the western subcluster and the primary cluster. We detect five X-ray surface brightness edges. Three of them near the cluster center are cold fronts (CFs): CF1 is associated with the infalling subcluster; CF2 is located in the east of the primary cluster and CF3 is to the west of the primary cluster core. The other two edges at cluster outskirts are shock fronts (SFs): SF1 near the radio relic in the NW has Mach numbers derived from the temperature and the density jumps respectively of MT = 1.62 ± 0.12 and Mρ = 1.23 ± 0.06; SF2 in the SE has MT = 1.54 ± 0.05 and Mρ = 1.16 ± 0.13. In the region of the radio relic there is no evidence for the correlation between X-ray and radio substructures, from which we estimate an upper limit for the inverse Compton emission, and therefore set a lower limit on the magnetic field (∼ 450 kpc from primary cluster center) of B > 1.0 μG for a single power-law electron spectrum or B > 0.4 μG for a broken power-law electron spectrum. We propose a merger scenario including a primary cluster, a subcluster, and a group. Our merger scenario accounts for the X-ray edges, diffuse radio features, and galaxy kinematics, as well as projection effects.

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“…Projection effects tend to underestimate M T and M ρ (e.g. Zhang et al 2019). On the other hand, the M T may also be biased high, if the pre-shock temperature is underestimated.…”

Section: Cfs and Merger Shocksmentioning

confidence: 99%

Chandra and XMM–Newton observations of A2256: cold fronts, merger shocks, and constraint on the IC emission

Liu

Sun

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…At t = 1.6 Gyr, the subcluster evolves to be a cone with an aperture of 40 • , which is similar with the observed conic structure. The fate of the conic subcluster in this simulation is the same as the one in Zhang et al (2019). After this epoch, the tip of the cone starts to expand in the low density outskirts.…”

Section: Conic Subclustermentioning

confidence: 90%

“…An analogy of the cone-shaped subcluster in simulations is presented in Fig. 9 of Zhang et al (2019) at t = 0.03 Gyr. As a bullet-like subcluster leaves the atmosphere of the main cluster, due to the decrease in pressure, the far end starts to expand while the two sides are still under ram pressure stripping.…”

Section: Conic Subclustermentioning

confidence: 99%

Deep Chandra observations of merging galaxy cluster ZwCl 2341+0000

Zhang

Simionescu

Stuardi

et al. 2021

A&A

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Context. Knowledge of X-ray shock and radio relic connection in merging galaxy clusters has been greatly extended in terms of both observation and theory over the last decade. ZwCl 2341+0000 is a double-relic merging galaxy cluster; previous studies have shown that half of the southern relic is associated with an X-ray surface brightness discontinuity, while the other half not. The discontinuity was believed to be a shock front. Therefore, it is a mysterious case of an only partial shock-relic connection. Aims. By using the 206.5 ks deep Chandra observations, we aim to investigate the nature of the southern surface brightness discontinuity. Meanwhile, we aim to explore new morphological and thermodynamical features. Methods. We perform both imaging and spectroscopic analyses to investigate the morphological and thermodynamical properties of the cluster. In addition to the X-ray data, we utilize the GMRT 325 MHz image and JVLA 1.5 GHz and 3.0 GHz images to compute radio spectral index maps. Results. Surface brightness profile fitting and the temperature profile suggest that the previously reported southern surface brightness discontinuity is better described as a sharp change in slope or as a kink. This kink is likely contributed by the disrupted core of the southern subcluster. The radio spectral index maps show spectral flattening at the south-eastern edge of the southern relic, suggesting that the location of the shock front is 640 kpc away from the kink, where the X-ray emission is too faint to detect a surface brightness discontinuity. We update the radio shock Mach number to be ℳradio, S = 2.2 ± 0.1 and ℳradio, N = 2.4 ± 0.4 for the southern and northern radio relics based on the injection spectral indices. We also put a 3σ lower limit on the X-ray Mach number of the southern shock to be ℳX-ray, S > 1.6. Meanwhile, the deep observations reveal that the northern subcluster is in a perfect cone shape, with a ∼400 kpc linear cold front on each side. This type of conic subcluster has been predicted by simulations but is observed here for the first time. It represents a transition stage between a blunt-body cold front and a slingshot cold front. Strikingly, we found a 400 kpc long gas trail attached to the apex of the cone, which could be due to the gas stripping. In addition, an over-pressured hot region is found in the south-western flank of the cluster.

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“…In extreme cases, such as that of Abell 2146 (Russell et al 2010), the difference can reach a factor of ten (Dasadia et al 2016). Recently, from simulations, Zhang et al (2019) found that the unexpectedly large stand-off distance can be due to de-acceleration of the cold front speed after the core passage, while the shock front can move faster.…”

Section: The Mystery Of the Southern Edgementioning

confidence: 99%

X-ray study of the merging galaxy cluster Abell 3411-3412 with XMM-Newton and Suzaku

Zhang

Simionescu

Akamatsu

et al. 2020

A&A

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Context. Previous Chandra observations of the Abell 3411-3412 merging galaxy cluster system revealed an outbound bullet-like sub-cluster in the northern part and many surface brightness edges at the southern periphery, where multiple diffuse sources are also reported from radio observations. Notably, a southeastern radio relic associated with fossil plasma from a radio galaxy and with a detected X-ray edge provides direct evidence of shock re-acceleration. The properties of the reported surface brightness features have yet to be constrained from a thermodynamic viewpoint. Aims. We use the XMM-Newton and Suzaku observations of Abell 3411-3412 to reveal the thermodynamical nature of the previously reported re-acceleration site and other X-ray surface brightness edges. We also aim to investigate the temperature profile in the low-density outskirts with Suzaku data. Methods. We performed both imaging and spectral analysis to measure the density jump and the temperature jump across multiple known X-ray surface brightness discontinuities. We present a new method to calibrate the vignetting function and spectral model of the XMM-Newton soft proton background. Archival Chandra, Suzaku, and ROSAT data are used to estimate the cosmic X-ray background and Galactic foreground levels with improved accuracy compared to standard blank sky spectra. Results. At the southeastern edge, temperature jumps revealed by both XMM-Newton and Suzaku point to a ℳ ∼ 1.2 shock, which agrees with the previous result from surface brightness fits with Chandra. The low Mach number supports the re-acceleration scenario at this shock front. The southern edge shows a more complex scenario, where a shock and the presence of stripped cold material may coincide. There is no evidence for a bow shock in front of the northwestern “bullet” sub-cluster. The Suzaku temperature profiles in the southern low-density regions are marginally higher than the typical relaxed cluster temperature profile. The measured value kT500 = 4.84 ± 0.04 ± 0.19 keV with XMM-Newton and kT500 = 5.17 ± 0.07 ± 0.13 keV with Suzaku are significantly lower than previously inferred from Chandra.

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Standoff distance of bow shocks in galaxy clusters as proxy for Mach number

Cited by 33 publications

References 23 publications

Chandra and XMM–Newton observations of A2256: cold fronts, merger shocks, and constraint on the IC emission

Chandra and XMM–Newton observations of A2256: cold fronts, merger shocks, and constraint on the IC emission

Deep Chandra observations of merging galaxy cluster ZwCl 2341+0000

X-ray study of the merging galaxy cluster Abell 3411-3412 with XMM-Newton and Suzaku

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