ORCID Profile
0000-0002-5851-5264
Current Organisations
University of Tasmania
,
CSIRO Astronomy and Space Science
,
CSIRO
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 3 Research Topics
ANZSRC Field of Research (FoR)
Astronomical and Space Sciences | Astronomical and Space Instrumentation
ANZSRC Socio-Economic Objective (SEO)
Related Links
Publications
WALLABY early science - V. ASKAP H I imaging of the Lyon Group of Galaxies 351
Publisher: Oxford University Press (OUP)
Date: 06-2019
Abstract: We present an H i study of the galaxy group LGG 351 using Widefield ASKAP L-band Legacy All-sky Blind Survey (WALLABY) early science data observed with the Australian Square Kilometre Array Pathfinder (ASKAP). LGG 351 resides behind the M 83 group at a velocity range (cz) of ∼3500–4800 km s−1 within the rich Hydra-Centaurus overdensity region. We detect 40 sources with the discovery of a tidally interacting galaxy pair and two new H i sources that are not presented in previous optical catalogues. 23 out of 40 sources have new redshifts derived from the new H i data. This study is the largest WALLABY sub-s le to date and also allows us to further validate the performance of ASKAP and the data reduction pipeline askapsoft. Extended H i emission is seen in six galaxies indicating interaction within the group, although no H i debris is found. We also detect H i in a known ultra-faint dwarf galaxy (dw 1328−29), which demonstrates that it is not a satellite of the M 83 group as previously thought. In conjunction with multiwavelength data, we find that our galaxies follow the atomic gas fraction and baryonic Tully–Fisher scaling relations derived from the GALEX Arecibo SDSS Survey. In addition, majority of our galaxies fall within the star formation main sequence indicating inefficiency of gas removal processes in this loose galaxy group.
e-VLBI observations of GRB 080409 afterglow with an Australasian radio telescope network
Publisher: IOP Publishing
Date: 11-2016
LUNASKA neutrino search with the Parkes and ATCA telescopes
Publisher: AIP
Date: 2013
DOI: 10.1063/1.4807514
A Keplerian disk with a four-arm spiral birthing an episodically accreting high-mass protostar
Publisher: Springer Science and Business Media LLC
Date: 27-02-2023
The first resolved imaging of milliarcsecond-scale jets in Circinus X-1
Publisher: Oxford University Press (OUP)
Date: 22-11-2011
A lunar radio experiment with the Parkes radio telescope for the LUNASKA project
Publisher: Elsevier BV
Date: 05-2015
PKS 1954–388: RadioAstron Detection on 80,000 km Baselines and Multiwavelength Observations
Publisher: Cambridge University Press (CUP)
Date: 2017
DOI: 10.1017/PASA.2017.16
Abstract: We present results from a multiwavelength study of the blazar PKS 1954–388 at radio, UV, X-ray, and gamma-ray energies. A RadioAstron observation at 1.66 GHz in June 2012 resulted in the detection of interferometric fringes on baselines of 6.2 Earth-diameters. This suggests a source frame brightness temperature of greater than 2 × 10 12 K, well in excess of both equipartition and inverse Compton limits and implying the existence of Doppler boosting in the core. An 8.4-GHz TANAMI VLBI image, made less than a month after the RadioAstron observations, is consistent with a previously reported superluminal motion for a jet component. Flux density monitoring with the Australia Telescope Compact Array confirms previous evidence for long-term variability that increases with observing frequency. A search for more rapid variability revealed no evidence for significant day-scale flux density variation. The ATCA light-curve reveals a strong radio flare beginning in late 2013, which peaks higher, and earlier, at higher frequencies. Comparison with the Fermi gamma-ray light-curve indicates this followed ~ 9 months after the start of a prolonged gamma-ray high-state—a radio lag comparable to that seen in other blazars. The multiwavelength data are combined to derive a Spectral Energy Distribution, which is fitted by a one-zone synchrotron-self-Compton (SSC) model with the addition of external Compton (EC) emission.
The first VLBI image of an infrared-faint radio source
Publisher: EDP Sciences
Date: 17-09-2008
Very long baseline interferometry detection of an Infrared-Faint Radio Source
Publisher: Oxford University Press (OUP)
Date: 16-06-2007
Potential kick velocity distribution of black hole X-ray binaries and implications for natal kicks
Publisher: Oxford University Press (OUP)
Date: 30-08-2019
Abstract: We use very long baseline interferometry to measure the proper motions of three black hole X-ray binaries (BHXBs). Using these results together with data from the literature and Gaia DR2 to collate the best available constraints on proper motion, parallax, distance, and systemic radial velocity of 16 BHXBs, we determined their three-dimensional Galactocentric orbits. We extended this analysis to estimate the probability distribution for the potential kick velocity (PKV) a BHXB system could have received on formation. Constraining the kicks imparted to BHXBs provides insight into the birth mechanism of black holes (BHs). Kicks also have a significant effect on BH–BH merger rates, merger sites, and binary evolution, and can be responsible for spin–orbit misalignment in BH binary systems. 75 per cent of our systems have potential kicks $\\gt 70\\, \\rm {km\\,s^{-1}}$. This suggests that strong kicks and hence spin–orbit misalignment might be common among BHXBs, in agreement with the observed quasi-periodic X-ray variability in their power density spectra. We used a Bayesian hierarchical methodology to analyse the PKV distribution of the BHXB population, and suggest that a unimodal Gaussian model with a mean of 107 $\\pm \\,\\,16\\, \\rm {km\\,s^{-1}}$ is a statistically favourable fit. Such relatively high PKVs would also reduce the number of BHs likely to be retained in globular clusters. We found no significant correlation between the BH mass and PKV, suggesting a lack of correlation between BH mass and the BH birth mechanism. Our python code allows the estimation of the PKV for any system with sufficient observational constraints.
A Search for H 2 O Maser Emission in Southern Active Galactic Nuclei and Star‐forming Galaxies: Discovery of a Maser in the Edge‐on Galaxy IRAS F01063−8034
Publisher: American Astronomical Society
Date: 02-2002
DOI: 10.1086/324383
Methanol Masers as Tracers of Circumstellar Disks
Publisher: American Astronomical Society
Date: 20-11-1998
DOI: 10.1086/306373
GASKAP-HI pilot survey science I: ASKAP zoom observations of Hi emission in the Small Magellanic Cloud
Publisher: Cambridge University Press (CUP)
Date: 2022
DOI: 10.1017/PASA.2021.59
Abstract: We present the most sensitive and detailed view of the neutral hydrogen ( ${\\rm H\\small I}$ ) emission associated with the Small Magellanic Cloud (SMC), through the combination of data from the Australian Square Kilometre Array Pathfinder (ASKAP) and Parkes (Murriyang), as part of the Galactic Australian Square Kilometre Array Pathfinder (GASKAP) pilot survey. These GASKAP-HI pilot observations, for the first time, reveal ${\\rm H\\small I}$ in the SMC on similar physical scales as other important tracers of the interstellar medium, such as molecular gas and dust. The resultant image cube possesses an rms noise level of 1.1 K ( $1.6\\,\\mathrm{mJy\\ beam}^{-1}$ ) $\\mathrm{per}\\ 0.98\\,\\mathrm{km\\ s}^{-1}$ spectral channel with an angular resolution of $30^{\\prime\\prime}$ ( ${\\sim}10\\,\\mathrm{pc}$ ). We discuss the calibration scheme and the custom imaging pipeline that utilises a joint deconvolution approach, efficiently distributed across a computing cluster, to accurately recover the emission extending across the entire ${\\sim}25\\,\\mathrm{deg}^2$ field-of-view. We provide an overview of the data products and characterise several aspects including the noise properties as a function of angular resolution and the represented spatial scales by deriving the global transfer function over the full spectral range. A preliminary spatial power spectrum analysis on in idual spectral channels reveals that the power law nature of the density distribution extends down to scales of 10 pc. We highlight the scientific potential of these data by comparing the properties of an outflowing high-velocity cloud with previous ASKAP+Parkes ${\\rm H\\small I}$ test observations.
Organometallic complexes for nonlinear optics. Part 29. Quadratic and cubic hyperpolarizabilities of stilbenylethynyl–gold and -ruthenium complexes
Publisher: Elsevier BV
Date: 07-2003
HI emission and absorption in nearby, gas-rich galaxies-II. Sample completion and detection of intervening absorption in NGC 5156
Publisher: Oxford University Press (OUP)
Date: 12-02-2016
Fringes on the EVN MkIV data processor at JIVE
Publisher: Elsevier BV
Date: 11-1999
e-VLBI observations of Circinus X-1: monitoring of the quiescent and flaring radio emission on au scales
Publisher: Oxford University Press (OUP)
Date: 17-05-2011
Water masers accompanying OH and methanol masers in star formation regions
Publisher: Oxford University Press (OUP)
Date: 05-2010
Do RadioAstron detections correlate with flaring states? An initial study of seven southern AGN
Publisher: Elsevier BV
Date: 2020
Detection statistics of the RadioAstron AGN survey
Publisher: Elsevier BV
Date: 2020
FIRST PARALLAX MEASUREMENTS TOWARD A 6.7 GHz METHANOL MASER WITH THE AUSTRALIAN LONG BASELINE ARRAY—DISTANCE TO G 339.884−1.259.
Publisher: American Astronomical Society
Date: 28-05-2015
HOPS: The H$_2$O Southern Galactic Plane Survey
Publisher: EDP Sciences
Date: 2011
DOI: 10.1051/EAS/1152021
Erratum: Discovery of H I gas in a young radio galaxy at z = 0.44 using the Australian Square Kilometre Array Pathfinder
Publisher: Oxford University Press (OUP)
Date: 31-12-2016
High‐Resolution Mid‐Infrared Imaging of G339.88−1.26
Publisher: American Astronomical Society
Date: 2002
DOI: 10.1086/324273
Limit on the ultrahigh-energy neutrino flux from lunar observations with the Parkes radio telescope
Publisher: American Physical Society (APS)
Date: 09-03-2015
LUNASKA experiments using the Australia Telescope Compact Array to search for ultrahigh energy neutrinos and develop technology for the lunar Cherenkov technique
Publisher: American Physical Society (APS)
Date: 26-02-2010
PKS 2250–351: A giant radio galaxy in Abell 3936
Publisher: Cambridge University Press (CUP)
Date: 2020
DOI: 10.1017/PASA.2019.49
Abstract: We present a detailed analysis of the radio galaxy PKS $2250{-}351$ , a giant of 1.2 Mpc projected size, its host galaxy, and its environment. We use radio data from the Murchison Widefield Array, the upgraded Giant Metre-wavelength Radio Telescope, the Australian Square Kilometre Array Pathfinder, and the Australia Telescope Compact Array to model the jet power and age. Optical and IR data come from the Galaxy And Mass Assembly (GAMA) survey and provide information on the host galaxy and environment. GAMA spectroscopy confirms that PKS $2250{-}351$ lies at $z=0.2115$ in the irregular, and likely unrelaxed, cluster Abell 3936. We find its host is a massive, ‘red and dead’ elliptical galaxy with negligible star formation but with a highly obscured active galactic nucleus dominating the mid-IR emission. Assuming it lies on the local M – $\\sigma$ relation, it has an Eddington accretion rate of $\\lambda_{\\rm EDD}\\sim 0.014$ . We find that the lobe-derived jet power (a time-averaged measure) is an order of magnitude greater than the hotspot-derived jet power (an instantaneous measure). We propose that over the lifetime of the observed radio emission ( ${\\sim} 300\\,$ Myr), the accretion has switched from an inefficient advection-dominated mode to a thin disc efficient mode, consistent with the decrease in jet power. We also suggest that the asymmetric radio morphology is due to its environment, with the host of PKS $2250{-}351$ lying to the west of the densest concentration of galaxies in Abell 3936.
LUNASKA experiment observational limits on UHE neutrinos from Centaurus A and the Galactic Centre
Publisher: Oxford University Press (OUP)
Date: 24-09-2010
A single fast radio burst localized to a massive galaxy at cosmological distance.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 09-08-2019
Abstract: Fast radio bursts (FRBs) are brief radio emissions from distant astronomical sources. Some are known to repeat, but most are single bursts. Nonrepeating FRB observations have had insufficient positional accuracy to localize them to an in idual host galaxy. We report the interferometric localization of the single-pulse FRB 180924 to a position 4 kiloparsecs from the center of a luminous galaxy at redshift 0.3214. The burst has not been observed to repeat. The properties of the burst and its host are markedly different from those of the only other accurately localized FRB source. The integrated electron column density along the line of sight closely matches models of the intergalactic medium, indicating that some FRBs are clean probes of the baryonic component of the cosmic web.
Mitochondrial DNA haplotypes induce differential patterns of DNA methylation that result in differential chromosomal gene expression patterns
Publisher: Springer Science and Business Media LLC
Date: 11-09-2017
DOI: 10.1038/CDDISCOVERY.2017.62
Abstract: Mitochondrial DNA copy number is strictly regulated during development as naive cells differentiate into mature cells to ensure that specific cell types have sufficient copies of mitochondrial DNA to perform their specialised functions. Mitochondrial DNA haplotypes are defined as specific regions of mitochondrial DNA that cluster with other mitochondrial sequences to show the phylogenetic origins of maternal lineages. Mitochondrial DNA haplotypes are associated with a range of phenotypes and disease. To understand how mitochondrial DNA haplotypes induce these characteristics, we used four embryonic stem cell lines that have the same set of chromosomes but possess different mitochondrial DNA haplotypes. We show that mitochondrial DNA haplotypes influence changes in chromosomal gene expression and affinity for nuclear-encoded mitochondrial DNA replication factors to modulate mitochondrial DNA copy number, two events that act synchronously during differentiation. Global DNA methylation analysis showed that each haplotype induces distinct DNA methylation patterns, which, when modulated by DNA demethylation agents, resulted in skewed gene expression patterns that highlight the effectiveness of the new DNA methylation patterns established by each haplotype. The haplotypes differentially regulate α -ketoglutarate, a metabolite from the TCA cycle that modulates the TET family of proteins, which catalyse the transition from 5-methylcytosine, indicative of DNA methylation, to 5-hydroxymethylcytosine, indicative of DNA demethylation. Our outcomes show that mitochondrial DNA haplotypes differentially modulate chromosomal gene expression patterns of naive and differentiating cells by establishing mitochondrial DNA haplotype-specific DNA methylation patterns.
γ-ray emission in radio galaxies under the VLBI scope
Publisher: EDP Sciences
Date: 09-2020
DOI: 10.1051/0004-6361/202038236
Abstract: Aims. This is the second paper in our series studying the evolution of parsec-scale radio emission in radio galaxies in the Southern Hemisphere. Following our study of the radio and high-energy properties of γ -ray-emitting sources, here we investigate the kinematic and spectral properties of the parsec-scale jets of radio galaxies that have not yet been detected by the Fermi Large Area Telescope ( Fermi -LAT) instrument on board NASA’s Fermi Gamma-ray Space Telescope. For many sources, these results represent the first milliarcsecond resolution information in the literature. These studies were conducted within the framework of the Tracking Active Nuclei with Austral Milliarcsecond Interferometry (TANAMI) monitoring program and in the context of high-energy γ -ray observations from Fermi -LAT. Methods. We took advantage of the regular 8.4 GHz and 22.3 GHz Very Long Baseline Interferometry (VLBI) observations provided by the TANAMI monitoring program, and explored the kinematic properties of six γ -ray-faint radio galaxies. We complemented this with ∼8.5 years of Fermi -LAT data, deriving updated upper limits on the γ -ray emission from this subs le of TANAMI radio galaxies. We included publicly available VLBI kinematics of γ -ray-quiet radio galaxies monitored by the MOJAVE program and performed a consistent Fermi -LAT analysis. We combined these results with those from our previous paper to construct the largest s le of radio galaxies with combined VLBI and γ -ray measurements to date. The connection between parsec-scale jet emission and high-energy properties in the misaligned jets of radio galaxies was explored. Results. For the first time, we report evidence of superluminal motion up to β app = 3.6 in the jet of the γ -ray-faint radio galaxy PKS 2153−69. We find a clear trend of higher apparent speed as a function of distance from the jet core, which indicates that the jet is still being accelerated on scales of tens of parsecs, or ∼10 5 R s , corresponding to the end of the collimation and acceleration zone in nearby radio galaxies. We find evidence of subluminal apparent motion in the jets of PKS 1258−321 and IC 4296, and no measurable apparent motion for PKS 1549−79, PKS 1733−565, and PKS 2027−308. For all these sources, TANAMI provides the first multi-epoch kinematic analysis on parsec scales. We then compare the VLBI properties of γ -ray-detected and undetected radio galaxies, and find that the two populations show a significantly different distribution of median core flux density, and, possibly, of median core brightness temperature. In terms of correlation between VLBI and γ -ray properties, we find a significant correlation between median core flux density and γ -ray flux, but no correlation with typical Doppler boosting indicators such as median core brightness temperature and core dominance. Conclusions. Our study suggests that high-energy emission from radio galaxies is related to parsec-scale radio emission from the inner jet, but is not driven by Doppler boosting effects, in contrast to the situation in their blazar counterparts. This implies that γ -ray loudness does not necessarily reflect a higher prevalence of boosting effects.
Deep space debris—Detection of potentially hazardous asteroids and objects from the southern hemisphere
Publisher: Frontiers Media SA
Date: 23-05-2023
DOI: 10.3389/FRSPT.2023.1162915
Abstract: Space debris are composed of both natural and human made objects, some in near Earth orbits while others are passing through deep space. Asteroids may represent one form of near Earth and deep space debris. In this article we report on a set of asteroid observations from the southern hemisphere. We indicate that Apollo and Aten class asteroids represent another form of deep space debris of a potentially hazardous nature to orbiting spacecraft and/or Earth based locations. We also show some of the operational challenges, types of facilities and the importance of geographic ersity, that is, necessary for detecting, observing and characterising asteroids, especially PHA’s. For many years, space agencies and institutions have observed and monitored near Earth asteroids and objects (NEO’s) using high gain radio frequency antennas and optical telescopes in the northern hemisphere (GSSR, Arecibo, Catalina, Pan-STARRS, Atlas and Linear) 1) However a regular operational system to monitor the southern skies does not have the same level of maturity and is where a percentage of asteroids and various human made objects are not detected until they pass into northern skies. To fill that gap the Southern Hemisphere Asteroid Radar Program (SHARP) 2) located in Australia uses available antenna time on either a 70 or 34 m beam waveguide antenna located at the Canberra Deep Space Communication Complex (CDSCC) to transmit a Doppler compensated continuous radio wave at 2.114 GHz (14.2 cm) and 7.15945 GHz (4.2 cm) toward the NEO and receive its echoes at the 64 m Parkes or 6 m × 22 m Australia Telescope Compact Array (ATCA) antennas at Narrabri in Australia. This mode of NEO observation is termed a deep space bistatic radar. The southern hemisphere program has also recently been joined by the 12 m University of Tasmania antennas at Hobart (Tasmania) and Katherine (Northern Territory). Combining SHARPS bistatic radar with small optical apertures located at the University of New South Wales (UNSW) and University of Western Australia (UWA) allows combined optical/RF NEO detections. Whilst sub-metre class optical instruments have contributed independently to asteroid detection over decades, the use of coordinated small 0.3–0.5 m instruments synchronized to large asteroid radars offers an observational flexibility and adaptability when larger optical systems 3) are dedicated to other forms of professional optical astronomy. Since 2015, SHARP has illuminated and tracked over 30 NEO’s ranging in diameter from 7 to 5000 m at ranges of 0.1–18 lunar distances (LD) from Australia.
Author Correction: A Keplerian disk with a four-arm spiral birthing an episodically accreting high-mass protostar
Publisher: Springer Science and Business Media LLC
Date: 16-03-2023
Radio and gamma-ray properties of extragalactic jets from the TANAMI sample
Publisher: EDP Sciences
Date: 04-05-2016
Discovery of H I gas in a young radio galaxy at z = 0.44 using the Australian Square Kilometre Array Pathfinder
Publisher: Oxford University Press (OUP)
Date: 24-08-2015
ANTARES constrains a blazar origin of two IceCube PeV neutrino events
Publisher: EDP Sciences
Date: 30-03-2015
Global e-VLBI observations of the gamma-ray narrow line Seyfert 1 PMN J0948+0022
Publisher: EDP Sciences
Date: 02-03-2011
Spectropolarimetric Analysis of FRB 181112 at Microsecond Resolution: Implications for Fast Radio Burst Emission Mechanism
Publisher: American Astronomical Society
Date: 12-03-2020
The Rapid ASKAP Continuum Survey I: Design and first results
Publisher: Cambridge University Press (CUP)
Date: 2020
DOI: 10.1017/PASA.2020.41
Abstract: The Rapid ASKAP Continuum Survey (RACS) is the first large-area survey to be conducted with the full 36-antenna Australian Square Kilometre Array Pathfinder (ASKAP) telescope. RACS will provide a shallow model of the ASKAP sky that will aid the calibration of future deep ASKAP surveys. RACS will cover the whole sky visible from the ASKAP site in Western Australia and will cover the full ASKAP band of 700–1800 MHz. The RACS images are generally deeper than the existing NRAO VLA Sky Survey and Sydney University Molonglo Sky Survey radio surveys and have better spatial resolution. All RACS survey products will be public, including radio images (with $\\sim$ 15 arcsec resolution) and catalogues of about three million source components with spectral index and polarisation information. In this paper, we present a description of the RACS survey and the first data release of 903 images covering the sky south of declination $+41^\\circ$ made over a 288-MHz band centred at 887.5 MHz.
An ultra-wide bandwidth (704 to 4 032 MHz) receiver for the Parkes radio telescope
Publisher: Cambridge University Press (CUP)
Date: 2020
DOI: 10.1017/PASA.2020.2
Abstract: We describe an ultra-wide-bandwidth, low-frequency receiver recently installed on the Parkes radio telescope. The receiver system provides continuous frequency coverage from 704 to 4032 MHz. For much of the band ( ${\\sim}60\\%$ ), the system temperature is approximately 22 K and the receiver system remains in a linear regime even in the presence of strong mobile phone transmissions. We discuss the scientific and technical aspects of the new receiver, including its astronomical objectives, as well as the feed, receiver, digitiser, and signal processor design. We describe the pipeline routines that form the archive-ready data products and how those data files can be accessed from the archives. The system performance is quantified, including the system noise and linearity, beam shape, antenna efficiency, polarisation calibration, and timing stability.
Status and strategies of current LUNASKA lunar Cherenkov observations with the Parkes radio telescope
Publisher: Elsevier BV
Date: 2012
High-velocity OH megamasers in IRAS 20100−4156: evidence for a supermassive black hole
Publisher: Oxford University Press (OUP)
Date: 06-05-2016
DOI: 10.1093/MNRAS/STW974
TANAMI monitoring of Centaurus A: The complex dynamics in the inner parsec of an extragalactic jet
Publisher: EDP Sciences
Date: 09-2014
The TANAMI Multiwavelength Program: Dynamic spectral energy distributions of southern blazars
Publisher: EDP Sciences
Date: 28-06-2016
The structure of the PA28–20S proteasome complex from Plasmodium falciparum and implications for proteostasis
Publisher: Springer Science and Business Media LLC
Date: 05-08-2019
DOI: 10.1038/S41564-019-0524-4
Abstract: The activity of the proteasome 20S catalytic core is regulated by protein complexes that bind to one or both ends. The PA28 regulator stimulates 20S proteasome peptidase activity in vitro, but its role in vivo remains unclear. Here, we show that genetic deletion of the PA28 regulator from Plasmodium falciparum (Pf) renders malaria parasites more sensitive to the antimalarial drug dihydroartemisinin, indicating that PA28 may play a role in protection against proteotoxic stress. The crystal structure of PfPA28 reveals a bell-shaped molecule with an inner pore that has a strong segregation of charges. Small-angle X-ray scattering shows that disordered loops, which are not resolved in the crystal structure, extend from the PfPA28 heptamer and surround the pore. Using single particle cryo-electron microscopy, we solved the structure of Pf20S in complex with one and two regulatory PfPA28 caps at resolutions of 3.9 and 3.8 Å, respectively. PfPA28 binds Pf20S asymmetrically, strongly engaging subunits on only one side of the core. PfPA28 undergoes rigid body motions relative to Pf20S. Molecular dynamics simulations support conformational flexibility and a leaky interface. We propose lateral transfer of short peptides through the dynamic interface as a mechanism facilitating the release of proteasome degradation products.
Measurement of the Rate Distribution of the Population of Repeating Fast Radio Bursts: Implications for Progenitor Models
Publisher: American Astronomical Society
Date: 22-05-2020
Which bright fast radio bursts repeat?
Publisher: Oxford University Press (OUP)
Date: 16-05-2020
Abstract: A handful of fast radio bursts (FRBs) are now known to repeat. However, the question remains – do they all? We report on an extensive observational c aign with the Australian Square Kilometre Array Pathfinder (ASKAP), Parkes, and Robert C. Byrd Green Bank Telescope, searching for repeat bursts from FRBs detected by the Commensal Real-time ASKAP Fast Transients survey. In 383.2 h of follow-up observations covering 27 FRBs initially detected as single bursts, only two repeat bursts from a single FRB, FRB 171019, were detected, which have been previously reported by Kumar et al. We use simulations of repeating FRBs that allow for clustering in burst arrival times to calculate new estimates for the repetition rate of FRB 171019, finding only slight evidence for incompatibility with the properties of FRB 121102. Our lack of repeat bursts from the remaining FRBs set limits on the model of all bursts being attributable to repeating FRBs. Assuming a reasonable range of repetition behaviour, at most 60 per cent (90 per cent confidence limit) of these FRBs have an intrinsic burst distribution similar to FRB 121102. This result is shown to be robust against different assumptions on the nature of repeating FRB behaviour, and indicates that if indeed all FRBs repeat, the majority must do so very rarely.
A common fold mediates vertebrate defense and bacterial attack
Publisher: American Association for the Advancement of Science (AAAS)
Date: 14-09-2007
Abstract: Proteins containing membrane attack complex erforin (MACPF) domains play important roles in vertebrate immunity, embryonic development, and neural-cell migration. In vertebrates, the ninth component of complement and perforin form oligomeric pores that lyse bacteria and kill virus-infected cells, respectively. However, the mechanism of MACPF function is unknown. We determined the crystal structure of a bacterial MACPF protein, Plu-MACPF from Photorhabdus luminescens , to 2.0 angstrom resolution. The MACPF domain reveals structural similarity with poreforming cholesterol-dependent cytolysins (CDCs) from Gram-positive bacteria. This suggests that lytic MACPF proteins may use a CDC-like mechanism to form pores and disrupt cell membranes. Sequence similarity between bacterial and vertebrate MACPF domains suggests that the fold of the CDCs, a family of proteins important for bacterial pathogenesis, is probably used by vertebrates for defense against infection.
TANAMI: Tracking Active Galactic Nuclei with Austral Milliarcsecond Interferometry
Publisher: EDP Sciences
Date: 02-2018
DOI: 10.1051/0004-6361/201731455
Abstract: Context. TANAMI is a multiwavelength program monitoring active galactic nuclei (AGN) south of − 30° declination including high-resolution very long baseline interferometry (VLBI) imaging, radio, optical/UV, X-ray, and γ -ray studies. We have previously published first-epoch8.4 GHz VLBI images of the parsec-scale structure of the initial s le. In this paper, we present images of 39 additional sources. The full s le comprises most of the radio- and γ -ray brightest AGN in the southern quarter of the sky, overlapping with the region from which high-energy ( 100 TeV) neutrino events have been found. Aims. We characterize the parsec-scale radio properties of the jets and compare them with the quasi-simultaneous Fermi /LAT γ -ray data. Furthermore, we study the jet properties of sources which are in positional coincidence with high-energy neutrino events compared to the full s le. We test the positional agreement of high-energy neutrino events with various AGN s les. Methods. TANAMI VLBI observations at 8.4 GHz are made with southern hemisphere radio telescopes located in Australia, Antarctica, Chile, New Zealand, and South Africa. Results. Our observations yield the first images of many jets below − 30° declination at milliarcsecond resolution. We find that γ -ray loud TANAMI sources tend to be more compact on parsec-scales and have higher core brightness temperatures than γ -ray faint jets, indicating higher Doppler factors. No significant structural difference is found between sources in positional coincidence with high-energy neutrino events and other TANAMI jets. The 22 γ -ray brightest AGN in the TANAMI sky show only a weak positional agreement with high-energy neutrinos demonstrating that the 100 TeV IceCube signal is not simply dominated by a small number of the γ -ray brightest blazars. Instead, a larger number of sources have to contribute to the signal with each in idual source having only a small Poisson probability for producing an event in multi-year integrations of current neutrino detectors.
Survival in a population sample is predicted by proportions of lymphocyte subsets.
Publisher: Elsevier BV
Date: 04-2003
DOI: 10.1016/S0047-6374(03)00021-6
Abstract: Comparisons of lymphocyte subsets show that the ratio of CD4 to CD8 is usually greater than one. Inversion of this ratio was found to predict survival in a Swedish octogenarian s le (n=27 deaths), although in idual lymphocyte subsets did not predict survival. We have examined these relationships in a larger s le (n=153 deaths). Inversion of the CD4 to CD8 ratio was present in 16% of the s le and predicted survival when adjusted for age but not when adjusted for sex. For in idual lymphocyte subsets, higher CD4 and CD19 percentages were associated with better survival, but only the CD19 percentage remained significant when adjusted for age and sex.
Detection of compact radio emission from Circinus X-1 with the first Southern hemisphere e-VLBI experiment
Publisher: Oxford University Press (OUP)
Date: 09-2007
Status report and future prospects on LUNASKA lunar observations with ATCA
Publisher: Elsevier BV
Date: 06-2009
A heatwave of accretion energy traced by masers in the G358-MM1 high-mass protostar
Publisher: Springer Science and Business Media LLC
Date: 13-01-2020
e-VLBI observations of GHz-peaked spectrum radio sources in nearby galaxies from the AT20G survey
Publisher: Oxford University Press (OUP)
Date: 21-08-2009
Parkes full polarization spectra of OH masers - I. Galactic longitudes 350° through the Galactic Centre to 41°
Publisher: Oxford University Press (OUP)
Date: 07-03-2013
DOI: 10.1093/MNRAS/STT239
Probing the microarcsecond structure of the Circinus megamasers through diffractive interstellar scintillation
Publisher: Oxford University Press (OUP)
Date: 02-2009
Parkes full polarization spectra of OH masers - II. Galactic longitudes 240° to 350°
Publisher: Oxford University Press (OUP)
Date: 07-02-2014
DOI: 10.1093/MNRAS/STU046
Extremely band-limited repetition from a fast radio burst source
Publisher: Oxford University Press (OUP)
Date: 05-11-2020
Abstract: The fast radio burst (FRB) population is observationally ided into sources that have been observed to repeat and those that have not. There is tentative evidence that the bursts from repeating sources have different properties than the non-repeating ones. In order to determine the occurrence rate of repeating sources and characterize the nature of repeat emission, we have been conducting sensitive searches for repetitions from bursts detected with the Australian Square Kilometre Array Pathfinder (ASKAP) with the 64-m Parkes radio telescope, using the recently commissioned Ultra-wideband Low (UWL) receiver system, over a band spanning 0.7–4.0 GHz. We report the detection of a repeat burst from the source of FRB 20190711A. The detected burst is 1 ms wide and has a bandwidth of just 65 MHz. We find no evidence of any emission in the remaining part of the 3.3 GHz UWL band. While the emission bandwidths of the ASKAP and UWL bursts show ν−4 scaling consistent with a propagation effect, the spectral occupancy is inconsistent with diffractive scintillation. This detection rules out models predicting broad-band emission from the FRB 20190711A source and puts stringent constraints on the emission mechanism. The low spectral occupancy highlights the importance of sub-banded search methods in detecting FRBs.
Parallaxes of 6.7-GHz methanol masers towards the G 305.2 high-mass star formation region
Publisher: Oxford University Press (OUP)
Date: 08-11-2016
Parkes observations for project P958 semester 2018APRS_07
Publisher: CSIRO
Date: 2018
Methanol masers and their environment at high resolution
Publisher: Oxford University Press (OUP)
Date: 11-1998
VLBI Observations of the Type I b/c Supernova 2009bb
Publisher: American Astronomical Society
Date: 15-11-2010
The Peculiar X-Ray Transient IGR J16358-4726
Publisher: American Astronomical Society
Date: 02-02-2004
DOI: 10.1086/382210
Crystalline Silicate Emission in the Protostellar Binary Serpens SVS 20
Publisher: American Astronomical Society
Date: 20-08-2005
DOI: 10.1086/431548
Faint Repetitions from a Bright Fast Radio Burst Source
Publisher: American Astronomical Society
Date: 17-12-2019
A survey of the Galactic plane for 6.7-GHz methanol masers - I. l=325 deg-335 deg b=-0.˚53-0.˚53
Publisher: Oxford University Press (OUP)
Date: 11-05-1996
The 6-GHz multibeam maser survey – II. Statistical analysis and Galactic distribution of 6668-MHz methanol masers
Publisher: Oxford University Press (OUP)
Date: 17-04-2017
DOI: 10.1093/MNRAS/STX887
The Detection of an Extremely Bright Fast Radio Burst in a Phased Array Feed Survey
Publisher: American Astronomical Society
Date: 22-05-2017
First search for low-frequency CH with a Square Kilometre Array precursor telescope
Publisher: Cambridge University Press (CUP)
Date: 2020
DOI: 10.1017/PASA.2020.48
Abstract: The diatomic free radical methylidyne (CH) is an important tracer of the interstellar medium, and the study of it was critical to our earliest understanding of star formation. Although it is detectable across the electromagnetic spectrum, observations at radio frequencies allow for a study of the kinematics of the diffuse and dense gas in regions of new star formation. There is only two published (single-dish) detections of the low-frequency hyperfine transitions between 700 and 725 MHz, despite the precise frequencies being known. These low-frequency transitions are of particular interest as they are shown in laboratory experiments to be more sensitive to magnetic fields than their high-frequency counterparts (with more pronounced Zeeman splitting). In this work, we take advantage of the radio quiet environment and increased resolution of the Australian Square Kilometre Array Pathfinder ( ASKAP ) over previous searches to make a pilot interferometric search for CH at 724.7883 MHz (the strongest of the hyperfine transitions) in RCW 38. We found the band is clean of radio frequency interference, but we did not detect the signal from this transition to a five-sigma sensitivity limit of 0.09 Jy, which corresponds to a total column density upper limit of 1.9 $\\times 10^{18}$ cm –2 for emission and 1.3 $\\times 10^{14}$ cm –2 for absorption with an optical depth limit of 0.95. Achieved within 5 h of integration, this column density sensitivity should have been adequate to detect the emission or absorption in RCW 38, if it had similar properties to the only previous reported detections in W51.
First Detection of Two Near‐Earth Asteroids With a Southern Hemisphere Planetary Radar System
Publisher: American Geophysical Union (AGU)
Date: 11-2017
DOI: 10.1002/2017RS006398
A comprehensive search for extragalactic 6.7-GHz methanol masers
Publisher: Oxford University Press (OUP)
Date: 02-1998
ASKAP detection of periodic and elliptically polarized radio pulses from UV Ceti
Publisher: Oxford University Press (OUP)
Date: 28-06-2019
Abstract: Active M dwarfs are known to produce bursty radio emission, and multiwavelength studies have shown that solar-like magnetic activity occurs in these stars. However, coherent bursts from active M dwarfs have often been difficult to interpret in the solar activity paradigm. We present Australian Square Array Pathfinder (ASKAP) observations of UV Ceti at a central frequency of 888 MHz. We detect several periodic, coherent pulses occurring over a time-scale consistent with the rotational period of UV Ceti. The properties of the pulsed emission show that they originate from the electron cyclotron maser instability, in a cavity at least 7 orders of magnitude less dense than the mean coronal density at the estimated source altitude. These results confirm that auroral activity can occur in active M dwarfs, suggesting that these stars mark the beginning of the transition from solar-like to auroral magnetospheric behaviour. These results demonstrate the capabilities of ASKAP for detecting polarized, coherent bursts from active stars and other systems.
Limits on Precursor and Afterglow Radio Emission from a Fast Radio Burst in a Star-forming Galaxy
Publisher: American Astronomical Society
Date: 24-09-2020
TANAMI blazars in the IceCube PeV-neutrino fields
Publisher: EDP Sciences
Date: 06-2014
Gamma-ray emission in radio galaxies under the VLBI scope
Publisher: EDP Sciences
Date: 07-2019
DOI: 10.1051/0004-6361/201935697
Abstract: Aims . In the framework of the multi-wavelength and very long baseline interferometry (VLBI) monitoring program TANAMI (Tracking Active Nuclei with Austral Milliarcsecond Interferometry), we study the evolution of the parsec-scale radio emission in radio galaxies in the southern hemisphere and their relationship to the γ -ray properties of the sources. Our study investigates systematically, for the first time, the relationship between the two energy regimes in radio galaxies. In this first paper, we focus on Fermi -LAT-detected sources. Methods . The TANAMI program monitors a large s le of radio-loud AGN at 8.4 GHz and 22.3 GHz with the Australian long baseline array (LBA) and associated telescopes in Antarctica, Chile, New Zealand and South Africa. We performed a kinematic analysis for five γ -ray detected radio galaxies using multi-epoch 8.4 GHz VLBI images, deriving limits on intrinsic jet parameters such as speed and viewing angle. We analyzed 103 months of Fermi -LAT data in order to study possible connections between the γ -ray properties and the pc-scale jets of Fermi -LAT-detected radio galaxies, both in terms of variability and average properties. We discuss the in idual source results and draw preliminary conclusions on s le properties including published VLBI results from the MOJAVE (Monitoring Of Jets in Active galactic nuclei with VLBA Experiments) survey, with a total of fifteen sources. Results . We find that the first γ -ray detection of Pictor A might be associated with the passage of a new VLBI component through the radio core, which appears to be a defining feature of high-energy emitting Fanaroff-Riley type II radio galaxies. We detect subluminal parsec-scale jet motions in the peculiar AGN PKS 0521−36, and we confirm the presence of fast γ -ray variability in the source down to timescales of six hours, which is not accompanied by variations in the VLBI jet. We robustly confirm the presence of significant superluminal motion, up to β app ∼ 3, in the jet of the TeV radio galaxy PKS 0625−35. Our VLBI results constrain the jet viewing angle to be θ 53°, allowing for the possibility of a closely aligned jet. Finally, by analyzing the first pc-scale multi-epoch images of the prototypical compact symmetric object (CSO) PKS 1718−649, we place an upper limit on the separation speed between the two mini-lobes. This in turn allows us to derive a lower limit on the age of the source. Conclusions. We can draw some preliminary conclusions on the relationship between pc-scale jets and γ -ray emission in radio galaxies, based on Fermi -LAT-detected sources with available multi-epoch VLBI measurements. We find that the VLBI core flux density correlates with the γ -ray flux, as seen in blazars. On the other hand, the γ -ray luminosity does not show any dependence on the core brightness temperature and core dominance, which are two common indicators of jet Doppler boosting. This seems to indicate that γ -ray emission in radio galaxies is not driven by orientation-dependent effects, as in blazars, in accordance with the unified model of jetted AGN.
Coincidence of a high-fluence blazar outburst with a PeV-energy neutrino event
Publisher: Springer Science and Business Media LLC
Date: 18-04-2016
DOI: 10.1038/NPHYS3715
The unusual multiwavelength properties of the gamma-ray source PMN J1603−4904
Publisher: EDP Sciences
Date: 30-01-2014
The Second LBA Calibrator Survey of southern compact extragalactic radio sources – LCS2
Publisher: Oxford University Press (OUP)
Date: 25-01-2019
DOI: 10.1093/MNRAS/STZ242
DiFX-2: A More Flexible, Efficient, Robust, and Powerful Software Correlator
Publisher: IOP Publishing
Date: 03-2011
DOI: 10.1086/658907
Maser emission in G 339.884-1.259
Publisher: Cambridge University Press (CUP)
Date: 09-2018
DOI: 10.1017/S1743921317010444
Abstract: We present multi–epoch VLBI observations of the methanol and water masers in the high–mass star formation region G 339.884−1.259, made using the Australian Long Baseline Array (LBA). Our sub–milliarcsecond precision measurements trace the proper motions of in idual maser features in the plane of the sky. When combined with the direct line–of–sight radial velocity ( v lsr ), these measure the 3 D gas kinematics of the associated high–mass star formation region, allowing us to probe the dynamical processes to within 1000 AU of the core.
Bistatic radar observations of near-earth asteroid (163899) 2003 SD220 from the southern hemisphere
Publisher: Elsevier BV
Date: 03-2021
The properties of extragalactic radio sources selected at 20 GHz
Publisher: Oxford University Press (OUP)
Date: 11-09-2006
Molecular line mapping of the giant molecular cloud associated with RCW 106 - I. $^13$CO
Publisher: Oxford University Press (OUP)
Date: 21-04-2006
The Statistics and Galactic Properties of the Methanol Multibeam Survey
Publisher: Cambridge University Press (CUP)
Date: 11-2009
DOI: 10.1017/S1743921310011786
Abstract: The methanol multi-beam (MMB) survey has produced the largest and most complete catalogue of Galactic 6.7-GHz methanol masers to date. 6.7-GHz methanol masers are exclusively associated with high-mass star formation, and as such provide invaluable insight into the Galactic distribution and properties of high-mass star formation regions. I present the statistical properties of the MMB catalogue and, through the calculation of kinematic distances, investigate the resolution of distance ambiguities and explore the Galactic distribution.
High time resolution and polarization properties of ASKAP-localized fast radio bursts
Publisher: Oxford University Press (OUP)
Date: 24-07-2020
Abstract: Combining high time and frequency resolution full-polarization spectra of fast radio bursts (FRBs) with knowledge of their host galaxy properties provides an opportunity to study both the emission mechanism generating them and the impact of their propagation through their local environment, host galaxy, and the intergalactic medium. The Australian Square Kilometre Array Pathfinder (ASKAP) telescope has provided the first ensemble of bursts with this information. In this paper, we present the high time and spectral resolution, full polarization observations of five localized FRBs to complement the results published for the previously studied ASKAP FRB 181112. We find that every FRB is highly polarized, with polarization fractions ranging from 80 to 100 per cent, and that they are generally dominated by linear polarization. While some FRBs in our s le exhibit properties associated with an emerging archetype (i.e. repeating or apparently non-repeating), others exhibit characteristic features of both, implying the existence of a continuum of FRB properties. When examined at high time resolution, we find that all FRBs in our s le have evidence for multiple subcomponents and for scattering at a level greater than expected from the Milky Way. We find no correlation between the erse range of FRB properties (e.g. scattering time, intrinsic width, and rotation measure) and any global property of their host galaxy. The most heavily scattered bursts reside in the outskirts of their host galaxies, suggesting that the source-local environment rather than the host interstellar medium is likely the dominant origin of the scattering in our s le.
RADIO OBSERVATIONS OF GRB 100418a: TEST OF AN ENERGY INJECTION MODEL EXPLAINING LONG-LASTING GRB AFTERGLOWS
Publisher: American Astronomical Society
Date: 27-11-2013
Parkes observations for project P958 semester 2018OCTS_BPSR_01
Publisher: CSIRO
Date: 2018
The Methanol Maser Emission in W51
Publisher: Springer Science and Business Media LLC
Date: 2005
PKS 1830−211: A Possible Compound Gravitational Lens
Publisher: American Astronomical Society
Date: 20-11-1996
DOI: 10.1086/310353
Water maser 353.273+0.641, the prime example of a class dominated by a blueshifted outflow
Publisher: Oxford University Press (OUP)
Date: 05-2008
VLBI OH maser polarimetry with the Australian Long Baseline Array: the star-forming region G340.054 0.244
Publisher: Cambridge University Press (CUP)
Date: 03-2007
DOI: 10.1017/S1743921307012574
Abstract: Until recently, high spatial resolution full Stokes maser polarimetry was the sole domain of northern interferometers and a wealth of sources in the far south remained unexplored due to a lack of suitable instrumentation having both high spatial and high velocity resolution. The Australia Telescope Long Baseline Array (LBA) has now switched to disk-based software correlation, permitting full Stokes observing in spectral line mode with velocity channels which are sufficiently narrow to s le usefully the polarization structure. To illustrate the utility of this valuable addition to radio astronomy, we present preliminary results of the first such polarimetric observation, the subject of which are the OH masers in the star-forming region G340.054–0.244.
A pilot ASKAP survey of radio transient events in the region around the intermittent pulsar PSR J1107-5907
Publisher: Oxford University Press (OUP)
Date: 14-01-2016
EVOLUTION OF THE PARSEC-SCALE STRUCTURE OF PKS 1934–638 REVISITED: FIRST SCIENCE WITH THE ASKAP AND NEW ZEALAND TELESCOPES
Publisher: American Astronomical Society
Date: 15-10-2010
The low density and magnetization of a massive galaxy halo exposed by a fast radio burst
Publisher: American Association for the Advancement of Science (AAAS)
Date: 11-10-2019
Abstract: Fast radio bursts (FRBs) are millisecond flashes of radio emission from distant galaxies. It has only recently become possible to locate single bursts precisely enough to determine the host galaxy. Prochaska et al. have observed and localized a FRB using a radio interferometer. The line of sight to the host galaxy coincidentally passes through the outskirts of a closer foreground galaxy. By analyzing the propagation of the FRB, the authors put constraints on the density and magnetization of gas in the outskirts of the foreground galaxy. The technique provides complementary information to existing methods using background quasars. Science , this issue p. 231
A census of baryons in the Universe from localized fast radio bursts
Publisher: Springer Science and Business Media LLC
Date: 27-05-2020
The ASKAP Variables and Slow Transients (VAST) Pilot Survey
Publisher: Cambridge University Press (CUP)
Date: 2021
DOI: 10.1017/PASA.2021.44
Abstract: The Variables and Slow Transients Survey (VAST) on the Australian Square Kilometre Array Pathfinder (ASKAP) is designed to detect highly variable and transient radio sources on timescales from 5 s to $\\sim\\!5$ yr. In this paper, we present the survey description, observation strategy and initial results from the VAST Phase I Pilot Survey. This pilot survey consists of $\\sim\\!162$ h of observations conducted at a central frequency of 888 MHz between 2019 August and 2020 August, with a typical rms sensitivity of $0.24\\ \\mathrm{mJy\\ beam}^{-1}$ and angular resolution of $12-20$ arcseconds. There are 113 fields, each of which was observed for 12 min integration time, with between 5 and 13 repeats, with cadences between 1 day and 8 months. The total area of the pilot survey footprint is 5 131 square degrees, covering six distinct regions of the sky. An initial search of two of these regions, totalling 1 646 square degrees, revealed 28 highly variable and/or transient sources. Seven of these are known pulsars, including the millisecond pulsar J2039–5617. Another seven are stars, four of which have no previously reported radio detection (SCR J0533–4257, LEHPM 2-783, UCAC3 89–412162 and 2MASS J22414436–6119311). Of the remaining 14 sources, two are active galactic nuclei, six are associated with galaxies and the other six have no multi-wavelength counterparts and are yet to be identified.
The gamma-ray emitting radio-loud narrow-line Seyfert 1 galaxy PKS 2004−447
Publisher: EDP Sciences
Date: 04-2016
Related Organisations
Commonwealth Scientific And Industrial Research Organisation
Location: Australia
Related Funding Activities
Linkage Infrastructure, Equipment And Facilities - Grant ID: LE200100201
Start Date: 08-2020
End Date: 08-2024
Amount: $530,000.00
Funder: Australian Research Council
View Funded Activity