A bright, high rotation-measure FRB that skewers the M33 halo
Abstract
We report the detection of a bright fast radio burst, FRB\,191108, with Apertif on the Westerbork Synthesis Radio Telescope (WSRT). The interferometer allows us to localise the FRB to a narrow ellipse by employing both multibeam information within the Apertif phased-array feed (PAF) beam pattern, and across different tied-array beams. The resulting sight line passes close to Local Group galaxy M33, with an impact parameter of only 18\,kpc with respect to the core. It also traverses the much larger circumgalactic medium of M31, the Andromeda Galaxy. We find that the shared plasma of the Local Group galaxies could contribute 10\% of its dispersion measure of 588\,pc\,cm. FRB\,191108 has a Faraday rotation measure of +474\,\,rad\,m, which is too large to be explained by either the Milky Way or the intergalactic medium. Based on the more moderate RMs of other extragalactic sources that traverse the halo of M33, we conclude that the dense magnetised plasma resides in the host galaxy. The FRB exhibits frequency structure on two scales, one that is consistent with quenched Galactic scintillation and broader spectral structure with \,MHz. If the latter is due to scattering in the shared M33/M31 CGM, our results constrain the Local Group plasma environment. We found no accompanying persistent radio sources in the Apertif imaging survey data.
Cite
@article{arxiv.2002.01399,
title = {A bright, high rotation-measure FRB that skewers the M33 halo},
author = {Liam Connor and Joeri van Leeuwen and L. C. Oostrum and E. Petroff and Yogesh Maan and E. A. K. Adams and J. J. Attema and J. E. Bast and O. M. Boersma and H. Dénes and D. W. Gardenier and J. E. Hargreaves and E. Kooistra and I. Pastor-Marazuela and R. Schulz and A. Sclocco and R. Smits and S. M. Straal and D. van der Schuur and Dany Vohl and B. Adebahr and W. J. G. de Blok and W. A. van Cappellen and A. H. W. M. Coolen and S. Damstra and G. N. J. van Diepen and B. S. Frank and K. M. Hess and B. Hut and G. Marcel Loose and D. M. Lucero and Á. Mika and V. A. Moss and H. Mulder and T. A. Oosterloo and M. Ruiter and H. Vedantham and N. J. Vermaas and S. J. Wijnholds and J. Ziemke},
journal= {arXiv preprint arXiv:2002.01399},
year = {2020}
}