Evidence for a hot galactic halo around the Andromeda Galaxy using fast radio bursts along two sightlines

Abstract

Fast Radio Bursts (FRBs) are millisecond-duration radio transients that serve as unique probes of ionized extragalactic matter. We report the discovery and localization of two FRBs piercing the Andromeda galaxy (M31) with the realfast transient-detection system at the Very Large Array. These unique sightlines enable constraints on M31's electron density distribution. We localized FRB 20230930A to a host galaxy at redshift $z=0.0925$ and FRB 20230506C to a host galaxy at redshift $z=0.3896$. After accounting for the dispersion contributions from the Milky Way, the host galaxies, and the intergalactic medium, we estimate M31's contribution to be $26-239$ $\mathrm{pc}\mathrm{c}{\mathrm{m}}^{-3}$ toward FRB 20230930A and $51-366$ $\mathrm{pc}\mathrm{c}{\mathrm{m}}^{-3}$ toward FRB 20230506C, within the 90% credible interval (CI). By modeling the M31 disk's contribution, we isolate the halo component and find that M31's halo contributes $7-169$ $\mathrm{pc}\mathrm{c}{\mathrm{m}}^{-3}$ along FRB 20230930A (90% CI). The inferred values of $\mathrm{D}{\mathrm{M}}_{M31,\mathrm{halo}}$ from the FRBs are consistent with predictions from a modified Navarro-Frenk-White (mNFW) profile at the corresponding impact parameter. The cool and warm phase gas is unlikely to account for the $\mathrm{D}{\mathrm{M}}_{M31,\mathrm{halo}}$ unless the ionization fraction is as high as 90%. While limited to two sightlines, these results offer tentative evidence for the existence of a hot halo surrounding M31. We also discuss the potential contribution of other foreground structures, particularly in explaining the DM excess observed in FRB 20230506C. This work demonstrates how FRBs can be used to probe the circumgalactic medium of intervening galaxies.

Published in ApJ

References in corpus (35)

• A bright millisecond radio burst of extragalactic origin
• Improving the full spectrum fitting method: accurate convolution with Gauss-Hermite functions
• The Circumgalactic Medium
• A New Electron Density Model for Estimation of Pulsar and FRB Distances
• The direct localization of a fast radio burst and its host
• Stellar Population Inference with Prospector
• A census of baryons in the Universe from localized fast radio bursts
• A repeating fast radio burst associated with a persistent radio source
• The low density and magnetization of a massive galaxy halo exposed by a fast radio burst
• Full spectrum fitting with photometry in pPXF: stellar population versus dynamical masses, non-parametric star formation history and metallicity for 3200 LEGA-C galaxies at redshift z~0.8
• Fully-Automated Reduction of Longslit Spectroscopy with the Low Resolution Imaging Spectrometer at Keck Observatory
• Probing Galactic Halos with Fast Radio Bursts
• Characterizing the FRB host galaxy population and its connection to transients in the local and extragalactic Universe
• Binospec: A Wide-field Imaging Spectrograph for the MMT
• Evidence for a Massive, Extended Circumgalactic Medium Around the Andromeda Galaxy
• A Distant Fast Radio Burst Associated to its Host Galaxy with the Very Large Array
• Project AMIGA: The Circumgalactic Medium of Andromeda
• An FRB Sent Me a DM: Constraining the Electron Column of the Milky Way Halo with Fast Radio Burst Dispersion Measures from CHIME/FRB
• Hot Extended Galaxy Halos Around Local L* Galaxies From Sunyaev-Zeldovich Measurements
• A sub-2% Distance to M31 from Photometrically Homogeneous Near-Infrared Cepheid Period-Luminosity Relations Measured with the Hubble Space Telescope
• A bright, high rotation-measure FRB that skewers the M33 halo
• Circumgalactic Oxygen Absorption and Feedback
• Relics of structure formation: extra-planar gas and high-velocity clouds around the Andromeda Galaxy
• The Commensal Real-time ASKAP Fast Transient incoherent-sum survey
• Deep Synoptic Array science: Two fast radio burst sources in massive galaxy clusters
• DBSP_DRP: A Python package for automated spectroscopic data reduction of DBSP data
• A measurement of circumgalactic gas around nearby galaxies using fast radio bursts
• VLA/Realfast Detection of a Burst from FRB180916.J0158+65 and Tests for Periodic Activity
• Your: Your Unified Reader
• An X-ray and SZ bright diffuse source toward M31: a Local Hot Bridge
• The Apertif Radio Transient System (ARTS): Design, Commissioning, Data Release, and Detection of the first 5 Fast Radio Bursts
• The Karl G. Jansky Very Large Array Local Group L-band Survey (LGLBS)
• Empirical estimation of host galaxy dispersion measure towards well localized fast radio bursts
• Modeling the Cosmic Dispersion Measure in the D < 120 Mpc Local Universe
• An unidentified Fermi source emitting radio bursts in the Galactic bulge