The low density and magnetization of a massive galaxy halo exposed by a fast radio burst

Abstract

Present-day galaxies are surrounded by cool and enriched halo gas extending for hundreds of kiloparsecs. This halo gas is thought to be the dominant reservoir of material available to fuel future star formation, but direct constraints on its mass and physical properties have been difficult to obtain. We report the detection of a fast radio burst (FRB 181112), localized with arcsecond precision, that passes through the halo of a foreground galaxy. Analysis of the burst shows that the halo gas has low net magnetization and turbulence. Our results imply predominantly diffuse gas in massive galactic halos, even those hosting active supermassive black holes, contrary to some previous results.

Spectropolarimetric Analysis of FRB 181112 at Microsecond Resolution: Implications for Fast Radio Burst Emission Mechanism

“…In this paper, we present a high time resolution analysis of FRB 181112 discovered as part of the Commensal Real-time ASKAP Fast Transients (CRAFT) survey (Macquart et al 2010). This burst was initially detected with a signal-to-noise ratio (S/N) of 19.3 in the CRAFT incoherent detection pipeline, in observations centred at 1297.5 MHz, with a measured duration of 2.1(2) ms and a fluence 26(3) Jy ms, as reported by Prochaska et al (2019). The burst was localized to a host galaxy at z = 0.4755 but, significantly, the line of sight also intercepted the halo of an intervening galaxy at z = 0.3674 at a transverse distance of 28 kpc.…”

“…We repeat this approach but with much finer time resolution in § 4.4, finding that the scattering time is ∼ 21 µs from the SGE α = −4 fit. We also have complementary information in the form of the frequency ACF which was not available to Prochaska et al (2019). The frequency ACF suggests that either the scattering time is 25 µs, or else 1 ns.…”

“…The cause of the highly luminous, millisecondtimescale emission of fast radio bursts (FRBs) is not understood. An increasing accumulation of bursts localized to host galaxies at cosmological distances, with redshifts over the range 0.19 < z < 0.66 (Chatterjee et al Corresponding author: Hyerin Cho chyerin1996@gmail.com 2017; Bannister et al 2019;Ravi et al 2019;Prochaska et al 2019), shows that their ∼ 10 35 K emission brightness temperatures are comparable to the coherent radiation of radio pulsars, but their 10 29 -10 33 erg Hz −1 spectral energy densities exceed those typically observed in pulsars by over ten orders of magnitude (Shannon et al 2018).…”

Magnetars from Neutron Star–White Dwarf Mergers: Application to Fast Radio Bursts

“…Compared with FRBs created from magnetars born in SLSNe/LGRBs channels, the FRBs produced from magnetars born in BNS/BWD/AIC channels could have a distinct observational properties. Just like FRBs 180924 and 190523, likely as well as FRB 181112 (Prochaska et al 2019), they host an old massive galaxy with a relatively low rate of star formation and relatively high metallicity, lie in a large spatially offset location relative to the central containment region of the galaxy, and have low DM and RM contributions from the host galaxy and no bright persistent radio source (Bannister et al 2019;Ravi et al 2019). If this is the case, FRBs could be divided into two populations: FRB 121102-like bursts stem from young magnetars born in SLSNe/LGRBs channels, while FRB 180924-like cases come from those young magnetars born in BNS/BWD/AIC channels.…”

“…Fast radio bursts (FRBs) have remained an extragalactic enigma so far (Katz 2018;Popov et al 2018;Petroff et al 2019;Cordes & Chatterjee 2019) since they were discovered by Lorimer et al (2007), Keane et al (2012), and Thornton et al (2013). They are millisecond-duration coherent radio pulses with average upper limits of the peak luminosity L p ∼ 1 × 10 42 − 8 × 10 44 erg s −1 and energy E ∼ 7 × 10 39 − 2 × 10 42 erg (Zhang 2018), characterized by a single peak mainly or multiple peaks rarely (Champion et al 2016;Farah et al 2018;Prochaska et al 2019), phenomenally divided into repeating bursts (Spitler et al 2016;CHIME/FRB Collaboration et al 2019a,b;Kumar et al 2019;CHIME/FRB Collaboration et al 2020) and non-repeating bursts.…”