Chandra and JVLA Observations of HST Frontier Fields Cluster MACS J0717.5+3745

Abstract

To investigate the relationship between thermal and non-thermal components in merger galaxy clusters, we present deep JVLA and Chandraobservations of the HST Frontier Fields cluster MACSJ0717.5+3745. The Chandraimage shows a complex merger event, with at least four components belonging to different merging subclusters. Northwestof the cluster, ∼0.7 Mpc from the center, there is a ram-pressure-stripped core that appears to have traversed the densest parts of the cluster after entering the intracluster medium (ICM) from the direction of a galaxy filament to the southeast. We detect a density discontinuity north-northeastof this core, which we speculate is associated with a cold front. Our radio images reveal new details for the complex radio relic and radio halo in this cluster. In addition, we discover several new filamentary radio sources with sizes of 100-300kpc. A few of these seem to be connected to the main radio relic, while others are either embedded within the radio halo or projected onto it. A narrow-angled-tailed (NAT) radio galaxy, a cluster member, is located at the center of the radio relic. The steep spectrum tails of this active galactic nucleuslead into the large radio relic where the radio spectrum flattens again. This morphological connection between the NAT radio galaxy and relic provides evidence for reacceleration (revival) of fossil electrons. The presence of hot 20 keV ICM gas detected by Chandranear the relic location provides additional support for this re-acceleration scenario.

Particle re-acceleration and Faraday-complex structures in the RXC J1314.4-2515 galaxy cluster

“…Overall, our analysis of the spectral index and polarization properties of the NAT and E relic supports the idea that remnants of radio lobes from AGN are strongly related to the origin of radio relics providing a fossil, low-energy (i.e., γ < 10 2 ) electron population (Markevitch et al 2005;Bonafede et al 2014;Kang & Ryu 2016;van Weeren et al 2017a).…”

“…At the same time JVLA allows us to study the diffuse radio emission in galaxy clusters on a variety of angular scales, and at different frequencies while keeping the same resolution. High-resolution spectral index images are important to obtain information on the life cycle of the relativistic electron that power radio sources (see, e.g., van Weeren et al 2017b).…”

Astrophysics with the Spatially and Spectrally Resolved Sunyaev-Zeldovich Effects

“…All figures apart from the lower right panel are from Korngut et al (2011). Lower-right panel is courtesy Reinout van Weeren, using MUSTANG data presented in Mroczkowski et al (2012) and Chandra + VLA data presented in van Weeren et al (2017). using NOBA data. The first sub-arcminute detection of a shock feature was provided by Korngut et al (2011), which used the pathfinder MUSTANG-1 bolometer array on the 100-meter Green Bank Telescope (GBT) to image MACS J0744.8+3927.…”

“…In addition to the emblematic case of RX J1347.5-1145, many other clusters were observed to study substructures using the tSZ effect. MUSTANG observations of the massive Frontier Fields cluster MACSJ0717.5+3745 (z = 0.55), which contains at least 4 merger components (Ma et al 2009;van Weeren et al 2017), revealed a high pressure region, presumably resulting from the merger of the 2 most massive components and likely driving and reshaping the southerly radio jet (see the lower-right panel of Figure 9). The shocked overpressure region is confirmed in X-ray observations, which indicate the presence of hot (> 18 keV) gas.…”

“…Another method is to cross-correlate measurements of the tSZ and kSZ effect with other tracers of large-scale structure such as lensing maps (Van Waerbeke et al 2014;Battaglia et al 2015b;Atrio-Barandela & Mücket 2017), galaxy surveys (Hernández-Monteagudo et al 2015), or the dispersion measures of fast radio bursts (Muñoz & Loeb 2018). Stacked measurements not only improve the signal to noise by increasing the effective integration time, but can also reduce certain forms of astrophysical contamination, as discussed in §5.3.…”