Showing papers by "Jean-Pierre Macquart published in 2019"
Australia Telescope National Facility1, Swinburne University of Technology2, Curtin University3, Institute for the Physics and Mathematics of the Universe4, University of California, Santa Cruz5, Pontifical Catholic University of Valparaíso6, Macquarie University7, University of Sydney8, University of Washington9, California Polytechnic State University10, University of Western Australia11, United States Naval Research Laboratory12, W.M. Keck Observatory13, University of California, Los Angeles14, Inter-University Centre for Astronomy and Astrophysics15, Australian National University16, ASTRON17
TL;DR: In this paper, the authors reported the interferometric localization of the single-pulse fast radio burst (FRB 180924) to a position 4 kiloparsecs from the center of a luminous galaxy at redshift 0.3214.
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 individual 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.
357 citations
Institute for the Physics and Mathematics of the Universe1, University of California, Santa Cruz2, Curtin University3, University of Washington4, Swinburne University of Technology5, Australia Telescope National Facility6, Macquarie University7, North Carolina State University8, Gwangju Institute of Science and Technology9, University of Sydney10, Pontifical Catholic University of Valparaíso11
TL;DR: In this article, the authors reported the detection of a fast radio burst (FRB 181112), localized with arcsecond precision, that passes through the halo of a foreground galaxy.
Abstract: Present-day galaxies are surrounded by cool and enriched halo gas extending for hundreds of kiloparsecs. This halo gas is thought to be the dominant reservoir of material available to fuel future star formation, but direct constraints on its mass and physical properties have been difficult to obtain. We report the detection of a fast radio burst (FRB 181112), localized with arcsecond precision, that passes through the halo of a foreground galaxy. Analysis of the burst shows that the halo gas has low net magnetization and turbulence. Our results imply predominantly diffuse gas in massive galactic halos, even those hosting active supermassive black holes, contrary to some previous results.
179 citations
Institute for the Physics and Mathematics of the Universe1, University of California, Berkeley2, Curtin University3, University of Washington4, Swinburne University of Technology5, Commonwealth Scientific and Industrial Research Organisation6, Macquarie University7, North Carolina State University8, Gwangju Institute of Science and Technology9, University of Sydney10, Pontifical Catholic University of Valparaíso11
TL;DR: In this article, the authors reported the detection of a fast radio burst (FRB 181112) with arcsecond precision, which passes through the halo of a foreground galaxy.
Abstract: Present-day galaxies are surrounded by cool and enriched halo gas extending to hundreds of kiloparsecs. This halo gas is thought to be the dominant reservoir of material available to fuel future star formation, but direct constraints on its mass and physical properties have been difficult to obtain. We report the detection of a fast radio burst (FRB 181112) with arcsecond precision, which passes through the halo of a foreground galaxy. Analysis of the burst shows the halo gas has low net magnetization and turbulence. Our results imply predominantly diffuse gas in massive galactic halos, even those hosting active supermassive black holes, contrary to some previous results.
144 citations
87 citations
TL;DR: In this paper, the authors reported the detection of repeat bursts from the source of FRB 171019, one of the brightest fast radio bursts (FRBs) detected in the Australian Square Kilometre Array Pathfinder (ASKAP) fly's eye survey.
Abstract: We report the detection of repeat bursts from the source of FRB 171019, one of the brightest fast radio bursts (FRBs) detected in the Australian Square Kilometre Array Pathfinder (ASKAP) fly's eye survey. Two bursts from the source were detected with the Green Bank Telescope in observations centered at 820 MHz. The repetitions are a factor of $\sim 590$ fainter than the ASKAP-discovered burst. All three bursts from this source show no evidence of scattering and have consistent pulse widths. The pulse spectra show modulation that could be evidence for either steep spectra or patchy emission. The two repetitions were the only ones found in an observing campaign for this FRB totaling 1000 hr, which also included ASKAP and the 64-m Parkes radio telescope, over a range of frequencies (720$-$2000 MHz) at epochs spanning two years. The inferred scaling of repetition rate with fluence of this source agrees with the other repeating source, FRB 121102. The detection of faint pulses from FRB 171019 shows that at least some FRBs selected from bright samples will repeat if follow-up observations are conducted with more sensitive telescopes.
87 citations
TL;DR: In this paper, the authors reported the detection of repeat bursts from the source of FRB 171019, one of the brightest fast radio bursts (FRBs) detected in the Australian Square Kilometre Array Pathfinder (ASKAP) fly's eye survey.
Abstract: We report the detection of repeat bursts from the source of FRB 171019, one of the brightest fast radio bursts (FRBs) detected in the Australian Square Kilometre Array Pathfinder (ASKAP) fly's eye survey. Two bursts from the source were detected with the Green Bank Telescope in observations centered at 820 MHz. The repetitions are a factor of $\sim 590$ fainter than the ASKAP-discovered burst. All three bursts from this source show no evidence of scattering and have consistent pulse widths. The pulse spectra show modulation that could be evidence for either steep spectra or patchy emission. The two repetitions were the only ones found in an observing campaign for this FRB totaling 1000 hr, which also included ASKAP and the 64-m Parkes radio telescope, over a range of frequencies (720$-$2000 MHz) at epochs spanning two years. The inferred scaling of repetition rate with fluence of this source agrees with the other repeating source, FRB 121102. The detection of faint pulses from FRB 171019 shows that at least some FRBs selected from bright samples will repeat if follow-up observations are conducted with more sensitive telescopes.
72 citations
TL;DR: In this paper, the authors extend the maximum-likelihood methods for estimating the source-count distribution of fast radio burst (FRB) fluences, using detected and threshold signal-to-noise ratios applied to all FRBs in a sample without regard to a completeness threshold.
Abstract: The slope of the source-count distribution of fast radio burst (FRB) fluences, $\alpha$, has been estimated using a variety of methods. Hampering all attempts have been the low number of detected FRBs, and the difficulty of defining a completeness threshold for FRB surveys. In this work, we extend maximum-likelihood methods for estimating $\alpha$, using detected and threshold signal-to-noise ratios applied to all FRBs in a sample without regard to a completeness threshold. Using this method with FRBs detected by the Parkes radio telescope, we find $\alpha=-1.18 \pm 0.24$ (68\% confidence interval, C.I.), i.e.\ consistent with a non-evolving Euclidean distribution ($\alpha=-1.5$). Applying these methods to the Australian Square Kilometre Array Pathfinder (ASKAP) Commensal Real-time ASKAP Fast Transients (CRAFT) FRB survey finds $\alpha=-2.2 \pm 0.47$ (68\% C.I.). A full maximum-likelihood estimate finds an inconsistency with the Parkes rate with a p-value of 0.86\% ($2.6\, \sigma$). If not due to statistical fluctuations or biases in Parkes data, this is the first evidence for deviations from a pure power law in the integral source-count distribution of FRBs. It is consistent with a steepening of the integral source-count distribution in the fluence range 5--40\,Jy\,ms, for instance due to a cosmological population of FRB progenitors evolving more rapidly than the star-formation rate, and peaking in the redshift range 1--3.
55 citations
TL;DR: In this paper, the distances of molecular clouds at high Galactic latitudes were derived from parallax and G band extinction measurements in the second Gaia data release, Gaia DR2.
Abstract: We report the distances of molecular clouds at high Galactic latitudes (|b|>10$^\circ$) derived from parallax and G band extinction (A$_{\rm G}$) measurements in the second Gaia data release, Gaia DR2. Aided by Bayesian analyses, we determined distances by identifying the breakpoint in the extinction A$_{\rm G}$ towards molecular clouds and using the extinction A$_{\rm G}$ of Gaia stars around molecular clouds to confirm the breakpoint. We use nearby star-forming regions, such as Orion, Taurus, Cepheus, and Perseus, whose distances are well-known to examine the reliability of our method. By comparing with previous results, we found that the molecular cloud distances derived from this method are reliable. The systematic error in the distances is approximately 5%. In total, 52 molecular clouds have their distances well determined, most of which are at high Galactic latitudes, and we provide reliable distances for 13 molecular clouds for the first time.
53 citations
TL;DR: In this article, the distances of molecular clouds at high Galactic latitudes (|b | > 10°) derived from parallax and G -band extinction (A G ) measurements in the second Gaia data release, Gaia DR2.
Abstract: We report the distances of molecular clouds at high Galactic latitudes (|b | > 10°) derived from parallax and G -band extinction (A G ) measurements in the second Gaia data release, Gaia DR2. Aided by Bayesian analyses, we determined distances by identifying the breakpoint in the extinction A G toward molecular clouds and using the extinction A G of Gaia stars around molecular clouds to confirm the breakpoint. We used nearby star-forming regions, such as Orion, Taurus, Cepheus, and Perseus, whose distances are well known to examine the reliability of our method. By comparing with previous results, we found that the molecular cloud distances derived from this method are reliable. The systematic error in the distances is approximately 5%. In total, 52 molecular clouds have well-determined distances, most of which are at high Galactic latitudes, and we provide reliable distances for 13 molecular clouds for the first time.
52 citations
Australia Telescope National Facility1, Swinburne University of Technology2, Curtin University3, University of California, Santa Cruz4, Institute for the Physics and Mathematics of the Universe5, Pontifical Catholic University of Valparaíso6, Macquarie University7, University of Sydney8, University of Washington9, California Polytechnic State University10, University of Western Australia11, United States Naval Research Laboratory12, W.M. Keck Observatory13, University of California, Los Angeles14, Inter-University Centre for Astronomy and Astrophysics15, Australian National University16, ASTRON17
TL;DR: Interferometric localization of the single-pulse FRB 180924 to a position 4 kiloparsecs from the center of a luminous galaxy at redshift 0.3214 indicates that some FRBs are clean probes of the baryonic component of the cosmic web.
Abstract: Fast Radio Bursts (FRBs) are brief radio emissions from distant astronomical sources. Some are known to repeat, but most are single bursts. Non-repeating FRB observations have had insufficient positional accuracy to localize them to an individual host galaxy. We report the interferometric localization of the single pulse FRB 180924 to a position 4 kpc 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 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.
45 citations
West Virginia University1, University of Sussex2, University of Cambridge3, Australia Telescope National Facility4, Swinburne University of Technology5, University of Massachusetts Amherst6, Millennium Institute7, Andrés Bello National University8, Pontifical Catholic University of Valparaíso9, University of Manchester10, Chinese Academy of Sciences11, University of KwaZulu-Natal12, Harvard University13
TL;DR: In this article, a targeted search for fast radio bursts near the core of the Virgo cluster using the Australian Square Kilometer Array Pathfinder telescope was described, and one burst, FRB 180417, was discovered during 300 hr of observations, with dispersion measure DM $=474.52$ (at 68\% confidence limit), and the minimum luminosity, $L_{\rm min}\gtrsim 2\times 10^{40}$ erg s$^{-1}$
Abstract: The rate of fast radio bursts (FRBs) in the direction of nearby galaxy clusters is expected to be higher than the mean cosmological rate if intrinsically faint FRBs are numerous. In this paper, we describe a targeted search for faint FRBs near the core of the Virgo cluster using the Australian Square Kilometer Array Pathfinder telescope. During 300 hr of observations, we discovered one burst, FRB 180417, with dispersion measure DM $=474.8$ cm$^{-3}$pc. The FRB was promptly followed up by several radio telescopes for 27 h, but no repeat bursts were detected. An optical follow-up of FRB 180417 using the PROMPT5 telescope revealed no new sources down to an $R$-band magnitude of 20.1. We argue that FRB 180417 is likely behind the Virgo cluster as the Galactic and intracluster DM contribution are small compared to the DM of the FRB, and there are no galaxies in the line of sight. The non-detection of FRBs from Virgo constrains the faint-end slope, $\alpha<1.52$ (at 68\% confidence limit), and the minimum luminosity, $L_{\rm min}\gtrsim 2\times 10^{40}$ erg s$^{-1}$ (at 68\% confidence limit), of the FRB luminosity function assuming cosmic FRB rate of $10^4$ FRBs sky$^{-1}$ day$^{-1}$ with flux above 1 Jy located out to redshift of 1. Further FRB surveys of galaxy clusters with high-sensitivity instruments will tighten the constraints on the faint end of the luminosity function and, thus, are strongly encouraged.
TL;DR: In this paper, the authors presented a calculation of the sensitivity and total exposure of the survey that detected the first 20 radio bursts, using the pulsars B1641-45 and B0833-45 as calibrators.
Abstract: The Commensal Real-time Australian Square Kilometre Array Pathfinder Fast Transients survey is the first extensive astronomical survey using phased array feeds. Since January 2017, it has been searching for fast radio bursts in fly’s eye mode. Here, we present a calculation of the sensitivity and total exposure of the survey that detected the first 20 of these bursts, using the pulsars B1641-45 and B0833-45 as calibrators. The beamshape, antenna-dependent system noise, and the effects of radio-frequency interference and fluctuations during commissioning are quantified. Effective survey exposures and sensitivities are calculated as a function of the source counts distribution. Statistical ‘stat’ and systematics ‘sys’ effects are treated separately. The implied fast radio burst rate is significantly lower than the 37 sky−1 day−1 calculated using nominal exposures and sensitivities for this same sample by Shannon et al. (2018). At the Euclidean (best-fit) power-law index of −1.5 (−2.2), the rate is (sys) ± 3.6 (stat) sky−1 day−1 ( (sys) ± 2.8 (stat) sky−1 day−1) above a threshold of 56.6 ± 6.6(sys) Jy ms (40.4 ± 1.2(sys) Jy ms). This strongly suggests that these calculations be performed for other FRB-hunting experiments, allowing meaningful comparisons to be made between them.
TL;DR: In this article, the authors measured the spectral scaling of the pulsar scattering timescale, α, from a single observation and found that the scattered profiles of both Vela and J0742-2822 are best described by a thin screen model where the Gum Nebula likely contributes most of the observed scattering delay.
Abstract: The high sensitivity and wide frequency coverage of the Murchison Widefield Array allow for the measurement of the spectral scaling of the pulsar scattering timescale, α, from a single observation. Here we present three case studies targeted at bright, strongly scattered pulsars J0534+2200 (the Crab pulsar), J0835-4510 (the Vela pulsar), and J0742-2822. We measure the scattering spectral indices to be -3.8 ±0.2, -4.0 ±1.5, and -2.5 ±0.6 for the Crab, Vela, and J0742-2822, respectively. We find that the scattered profiles of both Vela and J0742-2822 are best described by a thin screen model where the Gum Nebula likely contributes most of the observed scattering delay. For the Crab pulsar we see characteristically different pulse shapes compared to higher frequencies, for which none of the scattering screen models we explore are found to be optimal. The presence of a finite inner scale to the turbulence can possibly explain some of the discrepancies.
TL;DR: In this paper, the authors describe the parameters of a low-frequency all-sky survey of compact radio sources using interplanetary scintillation, undertaken with the Murchison Widefield Array.
Abstract: We describe the parameters of a low-frequency all-sky survey of compact radio sources using Interplanetary Scintillation, undertaken with the Murchison Widefield Array. While this survey gives important complementary information to low-resolution survey, providing information on the sub-arsecond structure of every source, a survey of this kind has not been attempted in the era of low-frequency imaging arrays such as the Murchison Widefield Array and LOw Frequency Array. Here we set out the capabilities of such a survey, describing the limitations imposed by the heliocentric observing geometry and by the instrument itself. We demonstrate the potential for Interplanetary Scintillation measurements at any point on the celestial sphere and we show that at 160 MHz, reasonable results can be obtained within 30° of the ecliptic (2π str: half the sky). We also suggest some observational strategies and describe the first such survey, the Murchison Widefield Array Phase I Interplanetary Scintillation survey. Finally we analyse the potential of the recently upgraded Murchison Widefield Array and discuss the potential of the Square Kilometre Array-low to use Interplanetary Scintillation to probe sub-mJy flux density levels at sub-arcsecond angular resolution.
TL;DR: In this paper, the authors measured the spectral indices of the Murchison Widefield Array (MWA) for three pulsars: the Crab, Vela and J0742-2822.
Abstract: The high sensitivity and wide frequency coverage of the Murchison Widefield Array allow for the measurement of the spectral scaling of the pulsar scattering timescale, $\alpha$, from a single observation. Here we present three case studies targeted at bright, strongly scattered pulsars J0534+2200 (the Crab pulsar), J0835-4510 (the Vela pulsar) and J0742-2822. We measure the scattering spectral indices to be $-3.8\pm0.2$, $-4.0\pm1.5$, and $-2.5\pm0.6$ for the Crab, Vela, and J0742-2822, respectively. We find that the scattered profiles of both Vela and J0742-2822 are best described by a thin screen model where the Gum Nebula likely contributes most of the observed scattering delay. For the Crab pulsar we see characteristically different pulse shapes compared to higher frequencies, for which none of the scattering screen models we explore are found to be optimal. The presence of a finite inner scale to the turbulence can possibly explain some of the discrepancies.