Search for: All records

Abstract This paper presents the first public data release (DR1) of the FRB Line-of-sight Ionization Measurement From Lightcone AAOmega Mapping (FLIMFLAM) survey, a wide field spectroscopic survey targeted on the fields of 10 precisely localized fast radio bursts (FRBs). DR1 encompasses spectroscopic data for 10,468 galaxy redshifts across 10 FRB fields withz < 0.4, covering approximately 26 deg²of the sky in total. FLIMFLAM is composed of several layers, encompassing the “wide” (covering ∼degree or >10 Mpc scales), “narrow” (several arcminutes or ∼Mpc), and integral field unit (“IFU”; ∼arcminute or ∼100 kpc) components. The bulk of the data comprises spectroscopy from the Two Degree Field-AAOmega instrument on the 3.9 m Anglo-Australian Telescope, while most of the narrow and IFU data was achieved using an ensemble of 8–10 m class telescopes. We summarize the information on our selected FRB fields, the criteria for target selection, methodologies employed for data reduction, spectral analysis processes, and an overview of our data products. An evaluation of our data reveals an average spectroscopic completeness of 48.43%, with over 80% of the observed targets having secure redshifts. Additionally, we describe our approach to generating angular masks and calculating the target selection functions, setting the stage for the impending reconstruction of the matter density field. 

Abstract Long-period radio transients are an emerging class of extreme astrophysical events of which only three are known. These objects emit highly polarized, coherent pulses of typically a few tens of seconds duration, and minutes to approximately hour-long periods. Although magnetic white dwarfs and magnetars, either isolated or in binary systems, have been invoked to explain these objects, a consensus has not emerged. Here we report on the discovery of ASKAP J193505.1+214841.0 (henceforth ASKAP J1935+2148) with a period of 53.8 minutes showing 3 distinct emission states—a bright pulse state with highly linearly polarized pulses with widths of 10–50 seconds; a weak pulse state that is about 26 times fainter than the bright state with highly circularly polarized pulses of widths of approximately 370 milliseconds; and a quiescent or quenched state with no pulses. The first two states have been observed to progressively evolve over the course of 8 months with the quenched state interspersed between them suggesting physical changes in the region producing the emission. A constraint on the radius of the source for the observed period rules out an isolated magnetic white-dwarf origin. Unlike other long-period sources, ASKAP 1935+2148 shows marked variations in emission modes reminiscent of neutron stars. However, its radio properties challenge our current understanding of neutron-star emission and evolution. 

Abstract The Macquart relation describes the correlation between the dispersion measure (DM) of fast radio bursts (FRBs) and the redshiftzof their host galaxies. The scatter of the Macquart relation is sensitive to the distribution of baryons in the intergalactic medium including those ejected from galactic halos through feedback processes. The variance of the distribution in DMs from the cosmic web (DM_cosmic) is parameterized by a fluctuation parameterF. In this work, we present a new measurement ofFusing 78 FRBs of which 21 have been localized to host galaxies. Our analysis simultaneously fits for the Hubble constantH₀and the DM distribution due to the FRB host galaxy. We find that the fluctuation parameter is degenerate with these parameters, most notablyH₀, and use a uniform prior onH₀to measure ${\log }_{10}F>-0.86$at the 3σconfidence interval and a new constraint on the Hubble constant $H_0={85.3}_{-8.1}^{+9.4}\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}$. Using a synthetic sample of 100 localized FRBs, the constraint on the fluctuation parameter is improved by a factor of ∼2. Comparing ourFmeasurement to simulated predictions from cosmological simulation (IllustrisTNG), we find agreement between redshifts 0.4 <z andz< 2.0. However, atz< 0.4, the simulations underpredictF, which we attribute to the rapidly changing extragalactic DM excess distribution at low redshift. 

Abstract Identification and follow-up observations of the host galaxies of fast radio bursts (FRBs) not only help us understand the environments in which the FRB progenitors reside, but also provide a unique way of probing the cosmological parameters using the dispersion measures (DMs) of FRBs and distances to their origin. A fundamental requirement is an accurate distance measurement to the FRB host galaxy, but for some sources viewed through the Galactic plane, optical/near-infrared spectroscopic redshifts are extremely difficult to obtain due to dust extinction. Here we report the first radio-based spectroscopic redshift measurement for an FRB host galaxy, through detection of its neutral hydrogen (Hi) 21 cm emission using MeerKAT observations. We obtain an Hi–based redshift ofz= 0.0357 ± 0.0001 for the host galaxy of FRB 20230718A, an apparently nonrepeating FRB detected in the Commensal Real-time ASKAP Fast Transients survey and localized at a Galactic latitude of –0.°367. Our observations also reveal that the FRB host galaxy is interacting with a nearby companion, which is evident from the detection of an Hibridge connecting the two galaxies. A subsequent optical spectroscopic observation confirmed an FRB host galaxy redshift of 0.0359 ± 0.0004. This result demonstrates the value of Hito obtain redshifts of FRBs at low Galactic latitudes and redshifts. Such nearby FRBs whose DMs are dominated by the Milky Way can be used to characterize these components and thus better calibrate the remaining cosmological contribution to dispersion for more distant FRBs that provide a strong lever arm to examine the Macquart relation between cosmological DM and redshift. 

Abstract We present a sample of nine fast radio bursts (FRBs) from which we derive magnetic field strengths of the host galaxies represented by normal,z< 0.5 star-forming galaxies with stellar massesM_*≈ 10⁸–10^10.5M_⊙. 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 a significant positive correlation (Spearman test probabilityP_S< 0.05) found between the RM and the estimated host dispersion measure (DM_host; with Spearman rank correlation coefficientr_S= +0.75). For these nine galaxies, we estimate their magnetic field strengths projected along the sight line ∣B_∥∣, finding a low median value of 0.5μG. This implies the magnetic fields of our sample of hosts are weaker than those characteristic of the solar neighborhood (≈6μG), but relatively consistent with a lower limit on the observed range of ≈2–10μG for star-forming disk galaxies, especially as we consider reversals in theB-field, and that we are only probing B_∥. 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 a 95% confidence interval. Upcoming FRB surveys will provide hundreds of new FRBs with high-precision localizations, RMs, and imaging follow-up to support further investigation into the magnetic fields of a diverse population ofz< 1 galaxies. 

ABSTRACT Fast radio bursts (FRBs) are transient radio signals of extragalactic origins that are subjected to propagation effects such as dispersion and scattering. It follows then that these signals hold information regarding the medium they have traversed and are hence useful as cosmological probes of the Universe. Recently, FRBs were used to make an independent measure of the Hubble constant H0, promising to resolve the Hubble tension given a sufficient number of detected FRBs. Such cosmological studies are dependent on FRB population statistics, cosmological parameters, and detection biases, and thus it is important to accurately characterize each of these. In this work, we empirically characterize the sensitivity of the Fast Real-time Engine for Dedispersing Amplitudes (FREDDA) which is the current detection system for the Australian Square Kilometre Array Pathfinder (ASKAP). We coherently redisperse high-time resolution data of 13 ASKAP-detected FRBs and inject them into FREDDA to determine the recovered signal-to-noise ratios as a function of dispersion measure. We find that for 11 of the 13 FRBs, these results are consistent with injecting idealized pulses. Approximating this sensitivity function with theoretical predictions results in a systematic error of 0.3 km s−1 Mpc−1 on H0 when it is the only free parameter. Allowing additional parameters to vary could increase this systematic by up to $$\sim 1\,$$ km s−1 Mpc−1. We estimate that this systematic will not be relevant until ∼400 localized FRBs have been detected, but will likely be significant in resolving the Hubble tension. 

ABSTRACT The HTRU-S Low Latitude survey data within 1° of the Galactic Centre (GC) were searched for pulsars using the Fast Folding Algorithm (FFA). Unlike traditional Fast Fourier Transform (FFT) pipelines, the FFA optimally folds the data for all possible periods over a given range, which is particularly advantageous for pulsars with low-duty cycles. For the first time, a search over acceleration was included in the FFA to improve its sensitivity to binary pulsars. The steps in dispersion measure (DM) and acceleration were optimized, resulting in a reduction of the number of trials by 86 per cent. This was achieved over a search period range from 0.6 to 432-s, i.e. 10 per cent of the observation time (4320s), with a maximum DM of 4000 pc cm−3 and an acceleration range of ±128 m s−2. The search resulted in the re-detections of four known pulsars, including a pulsar that was missed in the previous FFT processing of this survey. This result indicates that the FFA pipeline is more sensitive than the FFT pipeline used in the previous processing of the survey within our parameter range. Additionally, we discovered a 1.89-s pulsar, PSR J1746-2829, with a large DM, located 0.5 from the GC. Follow-up observations revealed that this pulsar has a relatively flat spectrum (α = −0.9 ± 0.1) and has a period derivative of ∼1.3 × 10−12 s s−1, implying a surface magnetic field of ∼5.2 × 1013 G and a characteristic age of ∼23 000 yr. While the period, spectral index, and surface magnetic field strength are similar to many radio magnetars, other characteristics such as high linear polarization are absent. 

Fast radio bursts (FRBs) are millisecond-duration pulses of radio emission originating from extragalactic distances. Radio dispersion is imparted on each burst by intervening plasma, mostly located in the intergalactic medium. In this work, we observe the burst FRB 20220610A and localize it to a morphologically complex host galaxy system at redshift 1.016 ± 0.002. The burst redshift and dispersion measure are consistent with passage through a substantial column of plasma in the intergalactic medium and extend the relationship between those quantities measured at lower redshift. The burst shows evidence for passage through additional turbulent magnetized plasma, potentially associated with the host galaxy. We use the burst energy of 2 × 10⁴²erg to revise the empirical maximum energy of an FRB. 

Informal learning has the potential to play an important role in helping children develop a life-long interest in STEM (Science, Technology, Engineering, and Mathematics). The goal of this review is to synthesize the evidence regarding the features of effective informal learning, provide effective ways to support learning within these contexts, and illustrate that cooking is an optimal opportunity for informal STEM learning. We review evidence demonstrating that the most effective informal learning activities are authentic, social and collaborative experiences that tap into culturally-relevant practices and knowledge, although there are limitations to each. We propose that cooking provides a context for authentic, culturally-relevant learning opportunities and includes natural supports for learning and engagement. Specifically, cooking provides many opportunities to apply STEM content (e.g., measuring and chemical reactions) to an existing foundation of knowledge about food. Cooking is also a family-based learning opportunity that exists across cultures, allows for in-home mentoring, and requires no specialized materials (beyond those available in most homes). It may help overcome some limitations in informal STEM learning, namely scalability. Finally, cooking provides immediate, tangible (and edible) results, promoting interest and supporting long-term engagement.