26 research outputs found
Deep Synoptic Array Science: Implications of Faraday Rotation Measures of Localized Fast Radio Bursts
Faraday rotation measures (RMs) of fast radio bursts (FRBs) offer the
prospect of directly measuring extragalactic magnetic fields. We present an
analysis of the RMs of ten as yet non-repeating FRBs detected and localized to
host galaxies by the 110-antenna Deep Synoptic Array (DSA-110). We combine this
sample with published RMs of 15 localized FRBs, nine of which are repeating
sources. For each FRB in the combined sample, we estimate the host-galaxy
dispersion measure (DM) contributions and extragalactic RM. We find compelling
evidence that the extragalactic components of FRB RMs are often dominated by
contributions from the host-galaxy interstellar medium (ISM). Specifically, we
find that both repeating and as yet non-repeating FRBs show a correlation
between the host-DM and host-RM in the rest frame, and we find an
anti-correlation between extragalactic RM (in the observer frame) and redshift
for non-repeaters, as expected if the magnetized plasma is in the host galaxy.
Important exceptions to the ISM origin include a dense, magnetized circum-burst
medium in some repeating FRBs, and the intra-cluster medium (ICM) of host or
intervening galaxy clusters. We find that the estimated ISM magnetic-field
strengths, , are characteristically larger than those inferred from
Galactic radio pulsars. This suggests either increased ISM magnetization in FRB
hosts in comparison with the Milky Way, or that FRBs preferentially reside in
regions of increased magnetic-field strength within their hosts
Deep Synoptic Array Science: Polarimetry of 25 New Fast Radio Bursts Provides Insights into their Origins
We report on a full-polarization analysis of the first 25 as yet
non-repeating FRBs detected at 1.4 GHz by the 110-antenna Deep Synoptic Array
(DSA-110) during commissioning observations. We present details of the data
reduction, calibration, and analysis procedures developed for this novel
instrument. The data have 32 s time resolution and sensitivity to Faraday
rotation measures (RMs) between rad m. RMs are detected for
20 FRBs with magnitudes ranging from rad m. FRBs are
found to have high () linear-polarization fractions. The remaining
FRBs exhibit significant circular polarization (), or are either
partially depolarized () or unpolarized (). We investigate the
mechanism of depolarization, disfavoring stochastic RM variations within a
scattering screen as a dominant cause. Polarization-state and possible RM
variations are observed in the four FRBs with multiple sub-components, but only
one other FRB shows a change in polarization state. We combine the DSA-110
sample with polarimetry of previously published FRBs, and compare the
polarization properties of FRB sub-populations and FRBs with Galactic pulsars.
Although FRBs are typically far more polarized than the average profiles of
Galactic pulsars, and exhibit greater spread in polarization fractions than
pulsar single pulses, we find a remarkable similarity between FRB polarization
fractions and the youngest (characteristic ages yr) pulsars. Our
results support a scenario wherein FRB emission is intrinsically highly
linearly polarized, and where propagation effects within progenitor
magnetospheres can result in conversion to circular polarization and
depolarization. Young pulsar emission and magnetospheric-propagation geometries
may form a useful analogy for the origin of FRB polarization.Comment: 43 pages, 17 figure
Deep Synoptic Array science I: discovery of the host galaxy of FRB 20220912A
We report the detection and interferometric localization of the repeating
fast radio burst (FRB) source FRB 20220912A during commissioning observations
with the Deep Synoptic Array (DSA-110). Two bursts were detected from FRB
20220912A, one each on 2022 October 18 and 2022 October 25. The best-fit
position is (R.A. J2000, decl. J2000) = (23:09:04.9, +48:42:25.4), with a 90%
confidence error ellipse of arcsec and arcsec in right ascension
and declination respectively. The two bursts have disparate polarization
properties and temporal profiles. We find a Faraday rotation measure that is
consistent with the low value of rad m reported by CHIME/FRB. The
DSA-110 localization overlaps with the galaxy PSO J347.2702+48.7066 at a
redshift , which we identify as the likely host. PSO
J347.270248.7066 has a stellar mass of approximately ,
modest internal dust extinction, and a star-formation rate likely in excess of
yr. The host-galaxy contribution to the dispersion
measure is likely pc cm. The FRB 20220912A source is
therefore likely viewed along a tenuous plasma column through the host galaxy.Comment: 10 pages, 7 figures, 2 tables, submitted to AAS Journal
Integrated genomic analyses of ovarian carcinoma
A catalogue of molecular aberrations that cause ovarian cancer is critical for developing and deploying therapies that will improve patients’ lives. The Cancer Genome Atlas project has analysed messenger RNA expression, microRNA expression, promoter methylation and DNA copy number in 489 high-grade serous ovarian adenocarcinomas and the DNA sequences of exons from coding genes in 316 of these tumours. Here we report that high-grade serous ovarian cancer is characterized by TP53 mutations in almost all tumours (96%); low prevalence but statistically recurrent somatic mutations in nine further genes including NF1, BRCA1, BRCA2, RB1 and CDK12; 113 significant focal DNA copy number aberrations; and promoter methylation events involving 168 genes. Analyses delineated four ovarian cancer transcriptional subtypes, three microRNA subtypes, four promoter methylation subtypes and a transcriptional signature associated with survival duration, and shed new light on the impact that tumours with BRCA1/2 (BRCA1 or BRCA2) and CCNE1 aberrations have on survival. Pathway analyses suggested that homologous recombination is defective in about half of the tumours analysed, and that NOTCH and FOXM1 signalling are involved in serous ovarian cancer pathophysiology.National Institutes of Health (U.S.) (Grant U54HG003067)National Institutes of Health (U.S.) (Grant U54HG003273)National Institutes of Health (U.S.) (Grant U54HG003079)National Institutes of Health (U.S.) (Grant U24CA126543)National Institutes of Health (U.S.) (Grant U24CA126544)National Institutes of Health (U.S.) (Grant U24CA126546)National Institutes of Health (U.S.) (Grant U24CA126551)National Institutes of Health (U.S.) (Grant U24CA126554)National Institutes of Health (U.S.) (Grant U24CA126561)National Institutes of Health (U.S.) (Grant U24CA126563)National Institutes of Health (U.S.) (Grant U24CA143882)National Institutes of Health (U.S.) (Grant U24CA143731)National Institutes of Health (U.S.) (Grant U24CA143835)National Institutes of Health (U.S.) (Grant U24CA143845)National Institutes of Health (U.S.) (Grant U24CA143858)National Institutes of Health (U.S.) (Grant U24CA144025)National Institutes of Health (U.S.) (Grant U24CA143866)National Institutes of Health (U.S.) (Grant U24CA143867)National Institutes of Health (U.S.) (Grant U24CA143848)National Institutes of Health (U.S.) (Grant U24CA143843)National Institutes of Health (U.S.) (Grant R21CA135877
Patterns of linkage disequilibrium and association mapping in diploid alfalfa (M. sativa L.)
Deep Synoptic Array Science: A Massive Elliptical Host Among Two Galaxy-cluster Fast Radio Bursts
The stellar population environments that are associated with fast radio burst (FRB) sources provide important insights for developing their progenitor theories. We expand the diversity of known FRB host environments by reporting two FRBs in massive galaxy clusters that were discovered by the Deep Synoptic Array (DSA-110) during its commissioning observations. FRB 20220914A has been localized to a star-forming, late-type galaxy at a redshift of 0.1139 with multiple starbursts at lookback times less than ∼3.5 Gyr in the A2310 galaxy cluster. Although the host galaxy of FRB 20220914A is similar to typical FRB hosts, the FRB 20220509G host stands out as a quiescent, early-type galaxy at a redshift of 0.0894 in the A2311 galaxy cluster. The discovery of FRBs in both late- and early-type galaxies adds to the body of evidence that the FRB sources have multiple formation channels. Therefore, even though FRB hosts are typically star-forming, there must exist formation channels that are consistent with old stellar population in galaxies. The varied star formation histories of the two FRB hosts that we report here indicate a wide delay-time distribution of FRB progenitors. Future work in constraining the FRB delay-time distribution, using the methods that we develop herein, will prove crucial in determining the evolutionary histories of FRB sources
Deep Synoptic Array Science: Implications of Faraday Rotation Measures of Fast Radio Bursts Localized to Host Galaxies
Faraday rotation measures (RMs) of fast radio bursts (FRBs) offer the prospect of directly measuring extragalactic magnetic fields. We present an analysis of the RMs of 10 as yet nonrepeating FRBs detected and localized to host galaxies with robust redshift measurements by the 63-antenna prototype of the Deep Synoptic Array (DSA-110). We combine this sample with published RMs of 15 localized FRBs, nine of which are repeating sources. For each FRB in the combined sample, we estimate the host-galaxy dispersion measure (DM) contributions and extragalactic RM. We find compelling evidence that the extragalactic components of FRB RMs are often dominated by contributions from the host-galaxy interstellar medium (ISM). Specifically, we find that both repeating and as yet nonrepeating FRBs show a correlation between the host DM and host RM in the rest frame, and we find an anticorrelation between extragalactic RM (in the observer frame) and redshift for nonrepeaters, as expected if the magnetized plasma is in the host galaxy. Important exceptions to the ISM origin include a dense, magnetized circumburst medium in some repeating FRBs, and the intracluster medium of host or intervening galaxy clusters. We find that the estimated ISM magnetic-field strengths, , are characteristically ∼1–2 μ G larger than those inferred from Galactic radio pulsars. This suggests either increased ISM magnetization in FRB hosts in comparison with the Milky Way, or that FRBs preferentially reside in regions of increased magnetic-field strength within their hosts