uGMRT detection of cluster radio emission in low-mass Planck Sunyaev–Zel’dovich clusters

Abstract

Low-mass (M500 < 5 × 1014 M⊙) galaxy clusters have been largely unexplored in radio observations, because of the inadequate sensitivity of existing telescopes. However, the upgraded Giant Metrewave Radio Telescope (uGMRT) and the Low Frequency ARray (LoFAR), with unprecedented sensitivity at low frequencies, have paved the way to study less massive clusters more closely than before. We have started the first large-scale programme to systematically search for diffuse radio emission from low-mass galaxy clusters, chosen from the Planck Sunyaev–Zel’dovich cluster catalogue. We report here the detection of diffuse radio emission from four of the 12 objects in our sample, shortlisted from the inspection of the LoFAR Two-Meter Sky Survey data release 1 (LoTSS-I), followed up by uGMRT Band 3 deep observations. The clusters PSZ2 G089 (Abell 1904) and PSZ2 G111 (Abell 1697) are detected with relic-like emission, while PSZ2 G106 is found to have an intermediate radio halo and PSZ2 G080 (Abell 2018) seems to be a halo-relic system. PSZ2 G089 and PSZ2 G080 are among the lowest-mass clusters discovered with a radio-relic and a halo-relic system, respectively. A high ($\sim \! 30{{\ \rm per\ cent}}$) detection rate, with powerful radio emission (P1.4 GHz ∼ 1023 W Hz−1) found in most of these objects, opens up prospects of studying radio emission in galaxy clusters over a wider mass range, to much lower-mass systems.

The Planck clusters in the LOFAR sky

“…PSZ2 G080.16+57.65 (A2018) A radio relic in the E direction was discovered together with a candidate radio halo by van Weeren et al (2021) in the analysis of the LoTSS-DR1 cluster sample. More recently, Paul et al (2021) confirmed the presence of the two sources using uGMRT data at 300−500 MHz. In this paper, we confirm only the presence of the radio relic.…”

Somewhere in between: Tracing the Radio Emission from Galaxy Groups (or Why Does the Future of Observing Galaxy Groups with Radio Telescopes Look Promising?)

“…The sensitivity of the LOFAR data allows for easily detecting radio emission from groups and low-mass clusters: since the release of the LoTSS DR1 data, numerous discoveries of an extended radio structure in a lightweight galaxy system have been reported (see, e.g., Botteon et al [59,60], Hoang et al [61], Knowles et al [62], Paul et al [63]). Very recently, Paul et al [64] has shown that the uGMRT data gathered at 400 MHz are complementary to those from the LoTSS and are also a powerful tool to undercover diffuse radio emission in low-mass clusters; detections were made in systems that are characterised by masses around 2-3 times larger than the theoretical upper limit for galaxy groups modelled by Paul et al [21]. This is a strong hint that the uGMRT can easily handle observing group radio emission too-offering not only excellent comparison data, but also a possibility to bring studies on the group magnetism to a whole new level: for example, by using the combined uGMRT and LOFAR data to create high-resolution maps of the strength of the magnetic field within the studied system.…”

Somewhere in between: Tracing the Radio Emission from Galaxy Groups (or Why Does the Future of Observing Galaxy Groups with Radio Telescopes Look Promising?)

“…The sensitivity of the LOFAR data allows to easily detect radio emission from groups and low-mass clusters: since the release of the LoTSS DR1 data, numerous discoveries of an extended radio structure in a lightweight galaxy system have been reported (see eg. Botteon [59] has shown that the uGMRT data gathered at 400 MHz are complementary to those from the LoTSS and are also a powerful tool to undercover diffuse radio emission in low-mass clusters; detections were made in systems that are characterised by masses around 2-3 times larger, than the theoretical upper limit for galaxy groups modelled by Paul et al [57]. This is a strong hint that the uGMRT can easily handle observing group radio emission, too -offering not only excellent comparison data, but also a possibility to bring studies on the group magnetism to a whole new level: for example, by using the combined uGMRT and LOFAR data to create high-resolution maps of the strength of the magnetic field within the studied system.…”