CJClancy William James

Clancy William James

Curtin University
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Clancy William James has a total of 1000 co-authors. Here are the top co-authors by number of shared publications:

Latest Publications

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    A fast radio burst at redshift 2, three billion years after the Big Bang

    by Manisha Caleb, Themiya Nanayakkara, Benjamin W. Stappers, Inés Pastor-Marazuela, Ilya S. Khrykin, Karl Glazebrook, Nicolas Tejos, J. Xavier Prochaska, Kaustubh Rajwade, Lluis Mas-Ribas, et al.

    Fast radio bursts (FRBs) are millisecond-duration radio transients from extragalactic sources. Their frequency and polarization properties are affected by plasma and magnetic fields along the line of sight to Earth. We report radio observations of FRB 20240304B and near-infrared follow-up to identify its host galaxy. The host is a low-mass, clumpy, star-forming galaxy at redshift 2.148 ± 0.0013, corresponding to 3 billion years after the Big Bang. This FRB occurred during the peak of cosmic star formation and probes ionized gas over approximately 80% of cosmic history. The highly scattered burst emission implies that there is a population of FRBs that are undetected by current surveys.

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    Detecting H i absorption in FRB spectra: Modern prospects and scientific utility

    by Hugh Roxburgh, Marcin Glowacki, Apurba Bera, Clancy James

    Fast radio bursts (FRBs) emit broadband radio emission that may, in rare cases, encode atomic hydrogen (H i ) absorption signals as they traverse the interstellar medium of their host galaxies. Though considered in the early FRB literature, the demanding observational prerequisites and the rarity of suitable events have meant that no thorough search for H i absorption in FRB spectra has yet been undertaken. Here, we present an updated systematic analysis assessing the likelihood of modern facilities to detect such absorption features. As a proof of concept, we search for absorption in the spectrum of the bright ASKAP-localised FRB 20211127I, finding a 3 sigma 3 σ $3\sigma$ opacity upper limit of 0.51. While this test case offers little constraining power, we find that narrow FRBs with fluences exceeding 20/70/150 Jy ms observed with MeerKAT/ASKAP/DSA can probe opacities below 0.1 – a regime in which absorption detections become physically meaningful. We further highlight that stacking thousands of bursts from hyperactive repeaters with FAST offers a very powerful avenue towards detection. Finally, we discuss the broad scientific potential of such detections, including constraints on extragalactic H i spin temperatures, a means to physically probe the environment surrounding the progenitor, and a path towards disentangling host galaxy contributions to dispersion and scattering.

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    Updating the PATH framework with FRB host galaxy models

    by C.W. James, N. Loudas, M. Woodland, B. C. Andersen, J. X. Prochaska, J.L. Hoffmann, L. Marnoch, S. D. Ryder

    Over a hundred fast radio burst (FRB) host galaxies have now been identified, enabling both comparisons of host redshift with FRB dispersion measure to study the cosmological distribution of ionised gas, and analyses of host properties in order to identify FRB progenitors. The standard method for determining the most likely FRB host galaxy in an optical image is the Bayesian framework Probabilistic Association of Transients to their Hosts (PATH), which accounts for uncertainties in the radio localisation, and simplified prior distributions on the host being observable. In this work we extend PATH, incorporating physically-motivated priors that are based on expectations about FRB host galaxy magnitudes. We develop three different models for the apparent r-band magnitude distribution based on an FRB’s expected host galaxy redshift, P ( m r | z ) and combine these with expectations for redshift based on an FRB’s dispersion measure, P ( z |DM). We fit the parameters of these prior models using host galaxy candidates for 32 FRBs detected by the Australian SKA Pathfinder (ASKAP) in incoherent sum (ICS) mode by the Commensal Real-time ASKAP Fast Transients (CRAFT) survey. Employing PATH with the new priors on the host magnitudes, we find increased confidence in the most probable hosts of all ASKAP ICS FRB host galaxies. All three models predict similar distributions of FRB host magnitudes at low redshift ( z ∼ 0.1), and we confirm previous results that the true FRB host galaxy distribution is fainter than expected for a star-formation-weighted distribution (p-value of 0.12%). However, a mass-weighted distribution provides an even worse fit (p-value of 10 −9 ). Tests against more FRBs in the z > 0.5 range, where the models differ, and extensions of the models to account for e.g. host metallicity, may help to resolve these uncertainties in the FRB host distribution.

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    Fast radio bursts in the era of the Vera C. Rubin Observatory’s Legacy Survey of Space and Time

    by C. W. James, B. Smith, K. Dage, A. L. Chies Santos, K. W. Bannister, M. Caleb, J. F. Crenshaw, A. T. Deller, K. G. Lee, L. Marnoch, et al.

    Comparing the redshifts of fast radio burst (FRB) host galaxies to FRB dispersion measures has unlocked a new probe of the cosmological distribution of ionised gas. However, the necessary optical observations to identify FRB hosts and measure their redshifts are becoming increasingly onerous. Here, we analyse the ability of the Legacy Survey of Space and Time (LSST), being conducted by the Vera C. Rubin Observatory, to identify FRB host galaxies, and the utility of LSST photometric redshifts for FRB cosmology. By combining a model of FRB host galaxy r -band magnitudes, m Subscript r m r $m_r$ , with predictions for the FRB z–DM distribution, we create a method to predict the m Subscript r Baseline left parenthesis z right parenthesis m r ( z ) $m_r(z)$ distribution for the host galaxies of FRBs detected by radio surveys. We then predict these distributions for the coherent modes of the Australian Square Kilometre Array Pathfinder (ASKAP) and MeerKAT. We find that even a single visit with Rubin will be able to identify 65% of FRB host galaxies detected by ASKAP’s coherent upgrade, ‘CRACO’; while the final 10 year co-added images will identify 81% of those from MeerKAT’s tied array beams. We find that estimated photo-z errors result in a decreased precision of only 7% on upper H 0 H 0 $H_0$ for ASKAP’s CRACO system. The impact of missing faint FRB hosts, however, will degrade sensitivity to upper H 0 H 0 $H_0$ by 47% or 62% when combined with photo-z errors. All told, Rubin’s LSST will be an incredibly powerful survey for facilitating FRB cosmology, although supplemental observations may be useful for particularly faint and distant host galaxies.

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    Constraining FRB microstructure with polarised shot noise

    by Joel C. F. Balzan, Apurba Bera, Clancy W. James, Bradley W. Meyers

    We present FIRES , a polarised shot-noise (PSN) framework that models fast radio burst (FRB) dynamic spectra as the incoherent superposition of Gaussian microshots with varying polarisation angles (PAs). Applied to the CRAFT bursts FRB 20191001A and FRB 20240318A, FIRES can reproduce key spectro-polarimetric behaviours seen in these data: scattering suppresses PA variability on the trailing edge, while the leading edge preferentially retains intrinsic structure when sufficient signal-to-noise is present. We quantify this behaviour using the PA variance ratio script upper R Subscript psi R ψ $\mathcal{R}_\psi$ and explore the joint plane of measured linear polarisation fraction normal upper Pi Subscript upper L Π L $\Pi_L$ versus PA variance to identify allowed regions of microshot number N , intrinsic PA dispersion sigma Subscript psi σ ψ $\sigma_\psi$ , and intrinsic linear fraction normal upper Pi Subscript upper L comma 0 Π L , 0 $\Pi_{L,0}$ at fixed signal-to-noise. This restricts these combinations permitted within the adopted shot-noise framework. For FRB 20191001A, the data are consistent with an extended parameter space, reflecting degeneracies between intrinsic PA structure, microshot superposition, scattering, finite sampling, noise, and the assumed microshot-property distributions. FRB 20240318A occupies a more restricted region, favouring fewer microshots and larger intrinsic PA dispersion. By combining an emission-mechanism-independent forward-modeling framework with minimal assumptions and observational constraints, FIRES facilitates qualitative and quantitative exploration of how microshot superposition, scattering, finite sampling, and noise can shape observed FRB polarimetry under the PSN model.

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    A particle detector array deployed to the Murchison Widefield Array in Inyarrimanha Ilgari Bundara, the Murchison Radio-astronomy Observatory

    by J. Edwin Dickinson, Justin D. Bray, David Kenney, Tom Booler, John Edgley, David Emrich, Amir R. Forouzan, Tegan Gould, Andrew McPhail, Paul Roberts, et al.

    We report the design and functionality of the Murchison Widefield Array Particle Detector Array (MWA PDA), an array of eight particle scintillation detectors deployed to Inyarrimanha Ilgari Bundara, the Murchison Radio-astronomy Observatory (MRO). The purpose of the instrument is to identify cosmic ray extensive air showers (EAS) occurring over the core of the MWA radio telescope and generate a trigger to allow radio data on the event to be captured and analysed. The system also acts as a pathfinder for a much larger instrument to be deployed in the core of the low-frequency component of the Square Kilometre Array, SKA-Low, by the SKA’s ultra-high-energy particles science working group. Here, we describe the instrument and associated infrastructure, which has been verified to comply with the strict radio-frequency emissions requirements of the MRO, and was deployed in November 2024. We present calibration data, which demonstrates the ability of each detector to identify individual atmospheric muons at the expected rate, and we characterise the temperature dependence of the system. We describe a sample of 35 500 EAS identified using multi-detector coincidence over a 13-d period, and show how the detector data can be used to reconstruct the arrival directions and approximate energies of these events. We conclude that the particle detector array can reliably trigger on and reconstruct EAS contained within the $\sim$ $103 \times 90$ m $^2$ core region, arriving within 20 $^{\circ}$ of zenith, at primary cosmic ray energies above $\sim$ 4 PeV. We have also verified that the detector array can generate triggers, allowing the capture of radio data from the MWA correlator for offline analysis.

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    The Low-mass Dwarf Host Galaxy of Nonrepeating FRB 20230708A

    by August R. Muller, Alexa C. Gordon, Stuart D. Ryder, Alexandra G. Mannings, J. Xavier Prochaska, Keith W. Bannister, A. Bera, Shivani Bhandari, N. D. R. Bhat, Adam T. Deller, et al.

    We present Very Large Telescope/X-Shooter spectroscopy for the host galaxies of 12 fast radio bursts (FRBs) detected by the Australian SKA Pathfinder observed through the “Fast and Unbiased FRB Host Galaxy (FURBY)” Large Programme at the European Southern Observatory, which imposes strict selection criteria on the included FRBs and their host galaxies to produce a homogeneous and well-defined sample. We describe the data reduction and analysis of these spectra and report their redshifts, line-emission fluxes, and derived host properties. From the present sample, this paper focuses on the faint host of FRB 20230708A ( m R = 22.53 ± 0.02) identified at low redshift ( z = 0.1050). This indicates an intrinsically very low-luminosity galaxy ( L ≈ 10 8 L ⊙ ), making it the lowest-luminosity nonrepeating FRB host to date by a factor of ∼3 and slightly dimmer than the lowest-luminosity host for repeating FRBs. Our spectral energy distribution fitting analysis reveals a low stellar mass ( M * ≈ 10 8.0 M ⊙ ), low star formation rate (SFR ≈ 0.04 M ⊙ yr −1 ), and very low metallicity( 12 + log ( O / H ) ∼ ( 8.0 − 8.3 ) ), distinct from the more massive galaxies (log( M / M ⊙ ) ∼ 10) that are commonly identified for nonrepeating FRBs. Its discovery demonstrates that FRBs can arise in the faintest, metal-poor galaxies of the Universe. In turn, this suggests that at least one FRB progenitor channel must include stars (or their remnants) created in very low metallicity environments. This indicates better prospects for detecting FRBs from the high- z Universe where young, low-mass galaxies proliferate.

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    Estimation of intrinsic fast radio burst width and scattering distributions from CRAFT data

    by Clancy William James, Jordan Luke Hoffmann, J. Xavier Prochaska, Marcin Glowacki

    The intrinsic width and scattering distributions of fast radio bursts (FRBs) inform on their emission mechanism and local environment, and act as a source of detection bias and, hence, an obfuscating factor when performing FRB population and cosmological studies. Here, we utilise a sample of 29 FRBs with measured high-time-resolution properties and known redshift, which were detected using the Australian Square Kilometre Array Pathfinder (ASKAP) by the Commensal Real-time ASKAP Fast Transients Survey (CRAFT), to model these distributions. Using this sample, we estimate the completeness bias of intrinsic width and scattering measurements and fit the underlying, de-biased distributions in the host rest-frame. In no case do our model fits prefer a down-turn at high values of the intrinsic distributions of either parameter in the 0.01–40 ms range probed by the data. Rather, when assuming a spectral scattering index of $\alpha = -4$ , we find that the intrinsic scattering distribution at 1 GHz is consistent with a log-uniform distribution above 0.04 ms and that this functional form is strongly favoured over the lognormal descriptions used by previous works. We also find that the intrinsic width distribution rises as a Gaussian in log-space in the 0.03 – 0.3 ms range, with a log-uniform distribution above that slightly preferred to a lognormal distribution. This confirms previous works suggesting that FRB observations are currently strongly width- and scattering-limited, and we encourage FRB searches to be extended to higher values of time-width. It also implies a bias in FRB host galaxy studies, although the form of that bias is uncertain. Finally, we find that our updated width and scattering models – when implemented in the zDM code – produces $\sim$ 10% more FRBs at redshift $z=1$ than at $z=0$ when compared to alternative width/scattering models, highlighting that these factors are important to understand when performing FRB population modelling.

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    A τ –DM Relation for Fast Radio Burst Hosts?

    by Lluis Mas-Ribas, Clancy W. James

    It has been proposed that measurements of scattering times ( τ ) from fast radio bursts (FRBs) may be used to infer the FRB host dispersion measure (DM) and its redshift. This approach relies on the existence of a correlation between τ and DM within FRB hosts such as that observed for Galactic pulsars. We assess the measurability of a τ –DM host relation through simulated observations of FRBs within the Australian Square Kilometre Array Pathfinder (ASKAP)/Commensal Real-time ASKAP Fast Transients (CRAFT) survey, taking into account instrumental effects. We show that even when the FRB hosts intrinsically follow the τ –DM relation measured for pulsars, this correlation cannot be inferred from FRB observations; this limitation arises mostly from the large variance around the average cosmic DM value given by the Macquart relation, the variance within the τ –DM relation itself, and observational biases against large τ values. We argue that theoretical relations have little utility as priors on redshift, e.g., for purposes of galaxy identification, and that the recent lack of an observed correlation between scattering and DM in the ASKAP/CRAFT survey is not unexpected, even if our understanding of a τ –DM host relation is correct.

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    I can see your halo: Constraining the MilkyWay halo DM with FRB population studies

    by Jordan Luke Hoffmann, Clancy James, Xavier Prochaska, Marcin Glowacki

    Fast radio bursts (FRBs) probe the electron column density along the line of sight and hence can be used to probe foreground structures. One such structure is the Galactic halo. In this work, we use a total of 98 high Galactic latitude ( $|b| \gt 20^\circ$ ) FRBs detected by ASKAP, Parkes, DSA, and FAST with 32 associated redshifts to constrain the dispersion measure (DM) contribution from the Galactic halo. We simultaneously fit unknown FRB population parameters, which show correlations with the Galactic halo but are not completely degenerate. We primarily use an isotropic model for the halo, but find no evidence favouring a particular halo model. We find DM $_\mathrm{MW,halo}$ = $68^{+27}_{-24}$ pc cm $^{-3}$ , which is in agreement with other results within the literature. Previous constraints on DM $_\mathrm{MW,halo}$ with FRBs have used a few, low-DM FRBs. However, this is highly subject to fluctuations between different lines of sight, and hence using a larger number of sightlines as we do is more likely to be representative of the true average contribution. Nevertheless, we show that individual FRBs can still skew the data significantly and hence will be important in the future for more precise results.

    Cited by 3
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