Australia: The Land Where Time Began

A biography of the Australian continent 

Fast Radio Burst Host Galaxy

In recent years, radio signals of millisecond duration that originate in distant galaxies have apparently been discovered in the so-called fast radio bursts (Lorimer et al., 2007; Keane et al., 2012; Thornton et al., 2013; Spitler et al., 2014; Burke-Spolaor & Bannister, 2014; Ravi, Shannon & Jameson, 2015; Petroff et al., 2015; Masui et al., 2015; Champion et al., 2015). These signals are dispersed according to a precise physical law and this is a key observable quantity, which, in tandem with a measurement of redshift can be used for fundamental physical investigations (McQuinn, 2014; Zhou et al., 2014). Every fast radio burst has a dispersion measurement, but this is the first to have a redshift measurement, as a result of the difficulty involved in pinpointing their celestial coordinates. In this paper Keane et al. report the discovery of a fast radio burst and the identification of a fading radio transient that lasted about 6 days following the event, which Keane et al. used to identify the host galaxy; they measured the redshift of the galaxy to be z = 0.492 ± 0.008. In combination, the dispersion measure and the redshift provide a direct measurement of the cosmic density of ionised baryons in the intergalactic medium of Ω_IGM = 4.9 ± 1.3 %, which agrees with the expectation from the Wilkinson Microwave Anisotropy Probe (Hinshaw et al., 2013), and including all the so-called ‘missing baryons’. According to Keane et al., the about 6 day radio transient is largely consistent with the radio afterglow of a short γ-ray burst (Hinshaw et al., 2013), and progenitor models such as giant pulses from pulsars and supernovae are not supported by its existence and timescale. This is in contrast with the interpretation (Masui et al., 2015) of another fast radio burst that was recently discovered, which suggests there are at least 2 classes of bursts.

Sources & Further reading

1. Keane, E. F., S. Johnston, S. Bhandari, E. Barr, N. D. R. Bhat, M. Burgay, M. Caleb, C. Flynn, A. Jameson, M. Kramer, E. Petroff, A. Possenti, W. van Straten, M. Bailes, S. Burke-Spolaor, R. P. Eatough, B. W. Stappers, T. Totani, M. Honma, H. Furusawa, T. Hattori, T. Morokuma, Y. Niino, H. Sugai, T. Terai, N. Tominaga, S. Yamasaki, N. Yasuda, R. Allen, J. Cooke, J. Jencson, M. M. Kasliwal, D. L. Kaplan, S. J. Tingay, A. Williams, R. Wayth, P. Chandra, D. Perrodin, M. Berezina, M. Mickaliger and C. Bassa (2016). "The host galaxy of a fast radio burst." Nature 530(7591): 453-456.