Search for low-frequency diffuse radio emission around a shock in the massive galaxy cluster MACS J0744.9+3927
Feb 19, 201810 pages
Published in:
- Mon.Not.Roy.Astron.Soc. 476 (2018) 3, 3415-3424
- Published: May 21, 2018
e-Print:
- 1802.06791 [astro-ph.CO]
DOI:
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Abstract: (Oxford University Press)
Merging galaxy clusters produce low-Mach-number shocks in the intracluster medium. These shocks can accelerate electrons to relativistic energies that are detectable at radio frequencies. MACS J0744.9+3927 is a massive [M_500 = (11.8 ± 2.8) × 10^14 M_⊙], high-redshift (z = 0.6976) cluster where a Bullet-type merger is presumed to have taken place. Sunyaev–Zel'dovich maps from MUSTANG indicate that a shock, with Mach number and an extension of ∼200 kpc, sits near the centre of the cluster. The shock is also detected as a brightness and temperature discontinuity in X-ray observations. To search for diffuse radio emission associated with the merger, we have imaged the cluster with the LOw Frequency ARray (LOFAR) at 120–165 MHz. Our LOFAR radio images reveal previously undetected AGN emission, but do not show clear cluster-scale diffuse emission in the form of a radio relic nor a radio halo. The region of the shock is on the western edge of AGN lobe emission from the brightest cluster galaxy. Correlating the flux of known shock-induced radio relics versus their size, we find that the radio emission overlapping the shocked region in MACS J0744.9+3927 is likely of AGN origin. We argue against the presence of a relic caused by diffusive shock acceleration and suggest that the shock is too weak to accelerate electrons from the intracluster medium.Note:
- 11 pages, 9 figures, accepted to MNRAS on February 13, 2018
- galaxies: clusters: general
- galaxies: clusters: individual: MACS J0744.9+3927
- galaxies: clusters: intracluster medium
- radio continuum: galaxies
References(98)
Figures(9)