28 research outputs found
First Constraints on Compact Dark Matter from Fast Radio Burst Microstructure
Despite existing constraints, it remains possible that up to of all
dark matter is comprised of compact objects, such as the black holes in the
10-100\,M range whose existence has been confirmed by LIGO. The strong
gravitational lensing of transients such as FRBs and GRBs has been suggested as
a more sensitive probe for compact dark matter than intensity fluctuations
observed in microlensing experiments. Recently ASKAP has reported burst
substructure down to s timescales in FRBs in the redshift range
. We investigate here the implications of this for the detectability
of compact dark matter by FRBs. We find that a sample size of FRBs
would be required to constrain compact dark matter to less than the existing
35 limit with 95 confidence, if it were distributed along Gpc-long FRB sightlines through the cosmic web. Conversely, existing
constraints on the fraction of compact dark matter permit as many as 1 in
of all FRBs to exhibit micro-lensed burst
structure. Approximately FRBs intercepting halos within kpc
would be required to exclude the fraction of compact dark matter in each
intercepted halo to a similar level. Furthermore, we consider the cumulative
effects of lensing of the FRB signal by a macroscopic dark matter distribution.
We conclude that lensing from a uniform distribution of compact objects is
likely not observable, but suggest that FRBs may set meaningful limits on
power-law distributions of dark matter.Comment: 3 Figures, 1 tabl
A search for supernova-like optical counterparts to ASKAP-localised Fast Radio Bursts
Fast radio bursts (FRBs) are millisecond-scale radio pulses, which originate
in distant galaxies and are produced by unknown sources. The mystery remains
partially because of the typical difficulty in localising FRBs to host
galaxies. Accurate localisations delivered by the Commensal Real-time ASKAP
Fast Transients (CRAFT) survey now provide an opportunity to study the host
galaxies and potential transient counterparts of FRBs at a large range of
wavelengths. In this work, we investigate whether the first three FRBs
accurately localised by CRAFT have supernova-like transient counterparts. We
obtained two sets of imaging epochs with the Very Large Telescope for three
host galaxies, one soon after the burst detection and one several months later.
After subtracting these images no optical counterparts were identified in the
associated FRB host galaxies, so we instead place limits on the brightness of
any potential optical transients. A Monte Carlo approach, in which supernova
light curves were modelled and their base properties randomised, was used to
estimate the probability of a supernova associated with each FRB going
undetected. We conclude that Type Ia and IIn supernovae are unlikely to
accompany every apparently non-repeating FRB.Comment: 7 pages, 3 figures. Accepted to Astronomy & Astrophysics on 03 June
202
The low density and magnetization of a massive galaxy halo exposed by a fast radio burst
Present-day galaxies are surrounded by cool and enriched halo gas extending
to 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) with arcsecond
precision, which passes through the halo of a foreground galaxy. Analysis of
the burst shows 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.Comment: Published in Science on 2019 September 26; Main (3 figures; 1 Table)
+ Supp (12 figures; 7 Tables
Limits on precursor and afterglow radio emission from a fast radio burst in a star-forming galaxy
We present a new fast radio burst at 920 MHz discovered during commensal
observations conducted with the Australian Square Kilometre Array Pathfinder
(ASKAP) as part of the Commensal Real-time ASKAP Fast Transients (CRAFT)
survey. FRB 191001 was detected at a dispersion measure (DM) of 506.92(4) pc
cm and its measured fluence of 143(15) Jy ms is the highest of the
bursts localized to host galaxies by ASKAP to date. The sub-arcsecond
localisation of the FRB provided by ASKAP reveals that the burst originated in
the outskirts of a highly star-forming spiral in a galaxy pair at redshift
. Radio observations show no evidence for a compact persistent
radio source associated with the FRB 191001 above a flux density of Jy.
However, we detect diffuse synchrotron radio emission from the disk of the host
galaxy that we ascribe to ongoing star formation. FRB 191001 was also detected
as an image-plane transient in a single 10-s snapshot with a flux density of
19.3 mJy in the low-time-resolution visibilities obtained simultaneously with
CRAFT data. The commensal observation facilitated a search for repeating and
slowly varying radio emissions 8 hrs before and 1 hr after the burst. We found
no variable radio emission on timescales ranging from 1 ms to 1.4 hr. We report
our upper limits and briefly review FRB progenitor theories in the literature
which predict radio afterglows. Our data are still only weakly constraining of
any afterglows at the redshift of the FRB. Future commensal observations of
more nearby and bright FRBs will potentially provide stronger constraints.Comment: 12 pages, 6 figures, Accepted for publication in ApJ Letter
Host Galaxy Properties and Offset Distributions of Fast Radio Bursts: Implications for Their Progenitors
We present observations and detailed characterizations of five new host galaxies of fast radio bursts (FRBs) discovered with the Australian Square Kilometre Array Pathfinder (ASKAP) and localized to βΎ 1". Combining these galaxies with FRB hosts from the literature, we introduce criteria based on the probability of chance coincidence to define a subsample of 10 highly confident associations (at z = 0.03β0.52), 3 of which correspond to known repeating FRBs. Overall, the FRB-host galaxies exhibit a broad, continuous range of color (M_u β M_r = 0.9β2.0), stellar mass (M_β
= 10βΈ β 6 Γ 10ΒΉβ° M_β), and star formation rate (SFR = 0.05β10 M_β yrβ»ΒΉ) spanning the full parameter space occupied by z 99% c.l.). We measure a median offset of 3.3 kpc from the FRB to the estimated center of the host galaxies and compare the host-burst offset distribution and other properties with the distributions of long- and short-duration gamma-ray bursts (LGRBs and SGRBs), core-collapse supernovae (CC-SNe), and SNe Ia. This analysis rules out galaxies hosting LGRBs (faint, star-forming galaxies) as common hosts for FRBs (>95% c.l.). Other transient channels (SGRBs, CC-, and SNe Ia) have host-galaxy properties and offsets consistent with the FRB distributions. All of the data and derived quantities are made publicly available on a dedicated website and repository
Host Galaxy Properties and Offset Distributions of Fast Radio Bursts: Implications for their Progenitors
We present observations and detailed characterizations of five new host
galaxies of fast radio bursts (FRBs) discovered with the Australian Square
Kilometre Array Pathfinder (ASKAP) and localized to . Combining
these galaxies with FRB hosts from the literature, we introduce criteria based
on the probability of chance coincidence to define a sub-sample of 10
highly-confident associations (at ), three of which correspond to
known repeating FRBs. Overall, the FRB host galaxies exhibit a broad,
continuous range of color (), stellar mass (), and star-formation rate () spanning the full parameter space
occupied by galaxies. However, they do not track the color-magnitude,
SFR-, nor BPT diagrams of field galaxies surveyed at similar
redshifts. There is an excess of "green valley" galaxies and an excess of
emission-line ratios indicative of a harder radiation field than that generated
by star-formation alone. From the observed stellar mass distribution, we rule
out the hypothesis that FRBs strictly track stellar mass in galaxies (
c.l.). We measure a median offset of 3.3 kpc from the FRB to the estimated
center of the host galaxies and compare the host-burst offset distribution and
other properties with the distributions of long- and short-duration gamma-ray
bursts (LGRBs and SGRBs), core-collapse supernovae (CC-SNe), and Type Ia SNe.
This analysis rules out galaxies hosting LGRBs (faint, star-forming galaxies)
as common hosts for FRBs ( c.l.). Other transient channels (SGRBs, CC-
and Type Ia SNe) have host galaxy properties and offsets consistent with the
FRB distributions. All of the data and derived quantities are made publicly
available on a dedicated website and repository.Comment: Accepted for publication in ApJ. All data are publicly available at
https://frbhosts.org and https://github.com/FRBs/FRB. Version 2 of manuscript
includes updated FRB uncertainty estimate