A single fast radio burst localized to a massive galaxy at cosmological distance (1906.11476v1)

Abstract: Fast Radio Bursts (FRBs) are brief radio emissions from distant astronomical sources. Some are known to repeat, but most are single bursts. Non-repeating FRB observations have had insufficient positional accuracy to localize them to an individual host galaxy. We report the interferometric localization of the single pulse FRB 180924 to a position 4 kpc from the center of a luminous galaxy at redshift 0.3214. The burst has not been observed to repeat. The properties of the burst and its host are markedly different from the only other accurately localized FRB source. The integrated electron column density along the line of sight closely matches models of the intergalactic medium, indicating that some FRBs are clean probes of the baryonic component of the cosmic web.

• The paper details the precise localization of FRB 180924 using ASKAP’s high-resolution interferometry, achieving position measurements with 0.12 arcsecond accuracy.
• The authors characterize the host galaxy as a massive, low star-formation lenticular type, sharply contrasting with previously localized dwarf galaxy hosts.
• The burst’s dispersion measure and polarization properties support its role as a probe of the intergalactic medium and the cosmic distribution of baryonic matter.

Overview of "A Single Fast Radio Burst Localized to a Massive Galaxy at Cosmological Distance"

This paper reports on the localization of a single fast radio burst (FRB), identified as FRB 180924, to a massive galaxy at a cosmological distance. Leveraging the capabilities of the Australian Square Kilometre Array Pathfinder (ASKAP), the authors have successfully pinpointed the origin of this FRB to 4 kiloparsecs from the center of a luminous galaxy at redshift 0.3214. This represents a seminal advancement in the field, as the localization of non-repeating FRBs has been notably challenging due to limited positional accuracy in previous observations.

Key Findings

1. Localization Methodology: The ASKAP, a 36-antenna radio interferometer, was utilized to achieve this localization. The paper describes a robust methodology involving a custom-built, phased-array beamforming system alongside a real-time detection pipeline that enabled the accurate positioning of FRB 180924 within its host galaxy. The interferometer's high angular resolution was crucial, allowing for position measurements with statistical precision up to 0.12 arcseconds.
2. Host Galaxy Characterization: The host of FRB 180924 is identified as a massive lenticular or early-type spiral galaxy with a stellar mass of approximately $2.2 \times 10^{10}$ solar masses and a minimal star formation rate, suggesting minimal ongoing stellar production. This discovery marks a stark contrast to the host galaxy of the only other accurately localized FRB before this paper, FRB 121102, which resides in a low-mass, high star-formation rate dwarf galaxy.
3. Burst Properties: The detected burst, with a dispersion measure (DM) of 361.42 pc cm$^-3$, exhibits a strong spectral modulation similar to previously discovered FRBs. Interestingly, the burst shows significant linear polarization with a modest rotation measure (RM), indicative of minimal magnetic field interactions along its path.
4. Cosmological and Astrophysical Implications: The results suggest that FRBs can serve as effective probes of the intergalactic medium, primarily serving to map the distribution of baryonic matter, which constitutes about 4% of the universe's energy density but often remains unaccounted for. This is corroborated by the alignment of the FRB's integrated electron column density with cosmic web models.

Contrasts with Previous FRBs

While FRB 121102, a repeating burst, was located in a star-forming dwarf galaxy, the non-repeating FRB 180924 emerged from an environment with vastly different galactic properties. This presents potential evidence for multiple progenitor classes of FRBs and poses critical questions regarding the environments conducive to FRB generation. The absence of repeated emissions from FRB 180924, despite rigorous observational campaigns, adds to this growing complexity.

Future Directions

This localization achievement hints at the vast potential of FRBs as tools for exploring cosmological phenomena. Future research may focus on identifying additional FRBs within entirely different galactic environments to better understand their origins and propagation mechanisms. Enhanced localization capabilities will also facilitate studies on the role of magnetic fields in intergalactic media and help refine existing cosmological models.

In summary, this paper significantly advances our understanding of FRBs, introducing novel techniques for precise localization and presenting compelling evidence of the varied astrophysical nature of FRB host galaxies. Further studies leveraging these methods could yield transformative insights into the universe's baryonic matter distribution and the enigmatic origins of fast radio bursts.