Radio stars and exoplanets at low-frequencies: first detections

Stars and planetary system

New constraints on the magnetic field in cosmic web filaments

Strong accretion shocks are expected to illuminate the warm-hot intergalactic medium encompassed by the filaments of the cosmic web, through synchrotron radio emission. Given their high sensitivity, large low-frequency radio facilities may already be able to detect signatures of this extended radio emission from the region between two close and massive galaxy clusters. In this work we exploit the non-detection of such diffuse emission by deep observations of two pairs of relatively close (similar or equal to 10 Mpc) and massive (M-500 >= 10(14) M-circle dot) galaxy clusters using the LOw-Frequency ARray. By combining the results from the two putative inter-cluster filaments, we derive new independent constraints on the median strength of intergalactic magnetic fields: B-10Mpc < 2.5 x 10(2) nG (95% confidence level). Based on cosmological simulations and assuming a primordial origin of the B-fields, these estimates can be used to limit the amplitude of primordial seed magnetic fields: B-0 <= 10 nG. We recommend the observation of similar cluster pairs as a powerful tool to set tight constraints on the amplitude of extragalactic magnetic fields.Large scale structure and cosmolog

A Massive Cluster at z = 0.288 Caught in the Process of Formation: The Case of Abell 959

The largest galaxy clusters are observed still to be forming through major cluster-cluster mergers, often showing observational signatures such as radio relics and giant radio haloes. Using LOFAR Two-meter Sky Survey data, we present new detections of both a radio halo (with a spectral index of $\alpha_{143}^{1400}=1.48^{+0.06}_{-0.23}$) and a likely radio relic in Abell 959, a massive cluster at a redshift of z=0.288. Using a sample of clusters with giant radio haloes from the literature (80 in total), we show that the radio halo in A959 lies reasonably well on the scaling relations between the thermal and non-thermal power of the system. Additionally, we find evidence that steep-spectrum haloes tend to reside in clusters with high X-ray luminosities relative to those expected from cluster LM scaling relations, indicating that such systems may preferentially lie at an earlier stage of the merger, consistent with the theory that some steep-spectrum haloes result from low-turbulence mergers. Lastly, we find that halo systems containing radio relics tend to lie at lower X-ray luminosities, relative to those expected from cluster LM scaling relations, for a given halo radio power than those without relics, suggesting that the presence of relics indicates a later stage of the merger, in line with simulations

Radio detection of chemically peculiar stars with LOFAR

Stars and planetary system

Connecting radio emission to AGN wind properties with broad absorption line quasars

Galaxie

LoTSS jellyfish galaxies: I. Radio tails in low redshift clusters

Galaxie