3 research outputs found
Fast Radio Bursts as Probes of Magnetic Fields in Galaxies at z < 0.5
We present a sample of nine Fast Radio Bursts (FRBs) from which we derive
magnetic field strengths of the host galaxies represented by normal,
star-forming galaxies with stellar masses . We find no correlation between the FRB rotation measure(RM) and
redshift which indicates that the RM values are due mostly to the FRB host
contribution. This assertion is further supported by strong correlations
(Spearman test probabilities ) found between RM and the
estimated host dispersion measure () and host-normalized
galacto-centric offset (Spearman values equal to 0.64 and -0.52). For
these nine galaxies, we estimate their magnetic field strengths projected along
the sightline finding a low median value of . This implies the
magnetic fields of our sample of hosts are weaker than those characteristic of
the Solar neighborhood (), but relatively consistent with a
lower limit on observed range of for star-forming, disk galaxies,
especially as we consider reversals in the B-field, and that we are only
probing . We compare to RMs from simulated galaxies of the
Auriga project -- magneto-hydrodynamic cosmological zoom simulations - and find
that the simulations predict the observed values to within the CI.
Upcoming FRB surveys will provide hundreds of new FRBs with high-precision
localizations, rotation measures, and imaging follow-up to support further
investigation on the magnetic fields of a diverse population of galaxies.Comment: 17 pages, 8 figures, 4 tables, Submitted to Ap
Mapping Obscured Star Formation in the Host Galaxy of FRB 20201124A
We present high-resolution 1.5--6 GHz Karl G. Jansky Very Large Array (VLA)
and () optical and infrared
observations of the extremely active repeating fast radio burst (FRB)
FRB20201124A and its barred spiral host galaxy. We constrain the location
and morphology of star formation in the host and search for a persistent radio
source (PRS) coincident with FRB20201124A. We resolve the morphology of the
radio emission across all frequency bands and measure a star formation rate SFR
yr, a factor of larger than
optically-inferred SFRs, demonstrating dust-obscured star formation throughout
the host. Compared to a sample of all known FRB hosts with radio emission, the
host of FRB20201124A has the most significant obscured star formation.
While observations show the FRB to be offset from the bar or spiral
arms, the radio emission extends to the FRB location. We propose that the FRB
progenitor could have formed (e.g., a magnetar central
engine born from the explosion of a massive star). It is still plausible,
although less likely, that the progenitor of FRB20201124A migrated from the
central bar of the host, e.g., via a runaway massive star. We further place a
limit on the luminosity of a putative PRS at the FRB position of $L_{\rm 6.0 \
GHz}\lesssim\times10^{27}^{-1}^{-1}\gtrsim 10^{5}$
yr in each model, respectively.Comment: 21 pages, 6 figures, 3 tables, Submitte
Measuring the Variance of the Macquart Relation in z-DM Modeling
The Macquart relation describes the correlation between the dispersion
measure (DM) of fast radio bursts (FRBs) and the redshift of their host
galaxies. The scatter of the Macquart relation is sensitive to the distribution
of baryons in the intergalactic medium (IGM) including those ejected from
galactic halos through feedback processes. The width of the distribution in DMs
from the cosmic web () is parameterized by a fluctuation
parameter , which is related to the cosmic DM variance by . In this work, we present a new measurement of using 78 FRBs of
which 21 have been localized to host galaxies. Our analysis simultaneously fits
for the Hubble constant and the DM distribution due to the FRB host
galaxy. We find that the fluctuation parameter is degenerate with these
parameters, most notably , and use a uniform prior on to measure
at the confidence interval and a new constraint
on the Hubble constant . Using a synthetic sample of 100 localized FRBs, the constraint on
the fluctuation parameter is improved by a factor of . Comparing our
measurement to simulated predictions from cosmological simulation
(IllustrisTNG), we find agreement between . However, at ,
the simulations underpredict which we attribute to the rapidly changing
extragalactic DM excess distribution at low redshift.Comment: Submitted to ApJ. 11 pages, 9 figures, 4 table