Search

We present the discovery of a single radio relic located at the edge of the galaxy cluster A2384, using the MeerKAT radio telescope. A2384 is a nearby (z = 0.092), low-mass, complex bimodal, merging galaxy cluster that displays a dense X-ray filament (∼700 kpc in length) between A2384(N; northern cluster) and A2384(S; southern cluster). The origin of the radio relic is puzzling. Using the MeerKAT observation of A2384, we estimate that the physical size of the radio relic is 824 × 264 kpc2 and that it is a steep spectrum source. The radio power of the relic is |$P_{1.4\mathrm{GHz}}\, \sim$| (3.87 ± 0.40) × 1023 W Hz−1. This radio relic could be the result of shock wave propagation during the passage of the low-mass A2384(S) cluster through the massive A2384(N) cluster, creating a trail appearing as a hot X-ray filament. In the previous GMRT 325 MHz observation, we detected a peculiar FR I radio galaxy interacting with the hot X-ray filament of A2384, but the extended radio relic was not detected; it was confused with the southern lobe of the FR I galaxy. This newly detected radio relic is elongated and perpendicular to the merger axis, as seen in other relic clusters. In addition to the relic, we notice a candidate radio ridge in the hot X-ray filament. The physical size of the radio ridge source is ∼182 × 129 kpc2. Detection of the diffuse radio sources in the X-ray filament is a rare phenomenon, and could be a new class of radio source found between the two merging clusters of A2384(N) and A2384(S). [ABSTRACT FROM AUTHOR]

We present VLA H  i observations of JO206, a prototypical ram-pressure-stripped galaxy in the GASP sample. This massive galaxy (M * = 8.5 × 1010 M⊙) is located at a redshift of z  = 0.0513, near the centre of the low-mass galaxy cluster, IIZw108 (σ ∼ 575  km s−1). JO206 is characterized by a long tail (≥90 kpc) of ionized gas stripped away by ram pressure. We find a similarly long H  i tail in the same direction as the ionized gas tail and measure a total H  i mass of 3.2 × 109 M⊙. This is about half the expected H  i mass given the stellar mass and surface density of JO206. A total of 1.8 × 109 M⊙ (60 per cent) of the detected H  i is in the gas-stripped tail. An analysis of the star formation rate shows that the galaxy is forming more stars compared to galaxies with the same stellar and H  i mass. On average we find an H  i gas depletion time of ∼0.5 Gyr which is about four times shorter than that of 'normal' spiral galaxies. We performed a spatially resolved analysis of the relation between star formation rate density and gas density in the disc and tail of the galaxy at the resolution of our H  i data. The star formation efficiency of the disc is about 10 times higher than that of the tail at fixed H  i surface densities. Both the inner and outer parts of JO206 show an enhanced star formation compared to regions of similar H  i surface density in field galaxies. The enhanced star formation is due to ram-pressure stripping during the galaxy's first infall into the cluster. [ABSTRACT FROM AUTHOR]