Fast radio burst event rate counts - I. Interpreting the observations

The fluence distribution of the fast radio burst (FRB) population (the 'source count' distribution, N ( > F) αF α ), is a crucial diagnostic of its distance distribution, and hence the progenitor evolutionary history. We critically reanalyse current estimates of the FRB source count distribution. We demonstrate that the Lorimer burst (FRB 010724) is subject to discovery bias, and should be excluded from all statistical studies of the population. We re-examine the evidence for flat, α > -1, source count estimates based on the ratio of single-beam to multiple-beam detections with the Parkes multibeam receiver, and show that current data imply only a very weak constraint of α ≲ -1.3. A maximum-likelihood analysis applied to the portion of the Parkes FRB population detected above the observational completeness fluence of 2 Jy ms yields α = -2.6 -1.3 +0.7 . Uncertainties in the location of each FRB within the Parkes beam render estimates of the Parkes event rate uncertain in both normalizing survey area and the estimated post-beam-corrected completeness fluence; this uncertainty needs to be accounted for when comparing the event rate against event rates measured at other telescopes

FRB event rate counts - II. Fluence, redshift, and dispersion measure distributions

We examine how the various observable statistical properties of the fast radio burst (FRB) population relate back to their fundamental physical properties in amodel-independent manner. We analyse the flux density and fluence distributions of FRBs as a tool to investigate their luminosity distance distribution and the evolution of their prevalence throughout cosmic history. We examine in detail particular scenarios in which the burst population follows some power of the cosmic star formation rate. FRBs present an important additional measurable over source counts of existing cosmological populations, namely the dispersion measure. Based on the known redshift of FRB121102 (the repeater) we expect at least 50 per cent of the dispersion measure to be attributable to the intergalactic medium and hence it can be used as a proxy for distance. We develop the framework to interpret the dispersion measure distribution, and investigate how the effect of Helium reionization in the intergalactic medium is evident in this distribution. Examination of existing data suggests that the FRB luminosity function is flatter than a critical slope, making FRBs easily detectable to large distances; in this regime the reduction in flux density with distance is outweighed by the increase in the number of bright bursts within the search volume

Ultra- and Hyper-compact HII regions at 20 GHz

We present radio and infrared observations of 4 hyper-compact HII regions and 4 ultra-compact HII regions in the southern Galactic plane. These objects were selected from a blind survey for UCHII regions using data from two new radio surveys of the southern sky; the Australia Telescope 20 GHz survey (AT20G) and the 2nd epoch Molonglo Galactic Plane Survey (MGPS-2) at 843 MHz. To our knowledge, this is the first blind radio survey for hyper- and ultra-compact HII regions. We have followed up these sources with the Australia Telescope Compact Array to obtain H70-alpha recombination line measurements, higher resolution images at 20 GHz and flux density measurements at 30, 40 and 95 GHz. From this we have determined sizes and recombination line temperatures as well as modeling the spectral energy distributions to determine emission measures. We have classified the sources as hyper-compact or ultra-compact on the basis of their physical parameters, in comparison with benchmark parameters from the literature. Several of these bright, compact sources are potential calibrators for the Low Frequency Instrument (30-70 GHz) and the 100-GHz channel of the High Frequency Instrument of the Planck satellite mission. They may also be useful as calibrators for the Australia Telescope Compact Array, which lacks good non-variable primary flux calibrators at higher frequencies and in the Galactic plane region. Our spectral energy distributions allow the flux densities within the Planck bands to be determined, although our high frequency observations show that several sources have excess emission at 95 GHz (3 mm) that can not be explained by current models.Comment: 13 pages, 7 figures, accepted for publication in MNRA

The Planck-ATCA Co-eval Observations (PACO) project: the bright sample

The Planck-ATCA Co-eval Observations (PACO) have provided flux density measurements of well defined samples of AT20G radio sources at frequencies below and overlapping with Planck frequency bands, almost simultaneously with Planck observations. We have observed with the Australia Telescope Compact Array (ATCA) a total of 482 sources in the frequency range between 4.5 and 40 GHz in the period between July 2009 and August 2010. Several sources were observed more than once. In this paper we present the aims of the project, the selection criteria, and the observation and data reduction procedures. We also discuss the data in total intensity for a complete sample of 189 sources with S(20 GHz)>500 mJy, Galactic latitude |b|>5deg, and declination <-30deg, and some statistical analysis of the spectral behaviour and variability of this sample, referred to as the "bright PACO sample". Finally we discuss how these data could be used to transfer absolute calibrations to ground based telescopes using the CMB dipole calibrated flux densities measured by the Planck satellite, and we provide some test fluxes on bright calibrators.Comment: 15 pages, 11 figure. Accepted for publication on MNRAS. Catalogue availabl

Joe Pawsey and the Founding of Australian Radio Astronomy

This open access book is a biography of Joseph L. Pawsey. It examines not only his life but the birth and growth of the field of radio astronomy and the state of science itself in twentieth century Australia. The book explains how an isolated continent with limited resources grew to be one of the leaders in the study of radio astronomy and the design of instruments to do so. Pawsey made a name for himself in the international astronomy community within a decade after WWII and coined the term radio astronomy. His most valuable talent was his ability to recruit and support bright young scientists who became the technical and methodological innovators of the era, building new telescopes from the Mills Cross and Chris (Christiansen) Cross to the Parkes radio telescope. The development of aperture synthesis and the controversy surrounding the cosmological interpretation of the first major survey which resulted in the Sydney research group's disagreements with Nobel laureate Martin Ryle play major roles in this story. This book also shows the connections among prominent astronomers like Oort, Minkowski, Baade, Struve, famous scientists in the UK such as J.A. Ratcliffe, Edward Appleton and Henry Tizard, and the engineers and physicists in Australia who helped develop the field of radio astronomy. Pawsey was appointed the second Director of the National Radio Astronomy Observatory (Green Bank, West Virginia) in October 1961; he died in Sydney at the age of 54 in late November 1962. Upper level students, scientists and historians will find the information, much of it from primary sources, relevant to any study of Joseph L. Pawsey or radio astronomy. This is an open access book

Joe Pawsey and the Founding of Australian Radio Astronomy

This open access book is a biography of Joseph L. Pawsey. It examines not only his life but the birth and growth of the field of radio astronomy and the state of science itself in twentieth century Australia. The book explains how an isolated continent with limited resources grew to be one of the leaders in the study of radio astronomy and the design of instruments to do so. Pawsey made a name for himself in the international astronomy community within a decade after WWII and coined the term radio astronomy. His most valuable talent was his ability to recruit and support bright young scientists who became the technical and methodological innovators of the era, building new telescopes from the Mills Cross and Chris (Christiansen) Cross to the Parkes radio telescope. The development of aperture synthesis and the controversy surrounding the cosmological interpretation of the first major survey which resulted in the Sydney research group's disagreements with Nobel laureate Martin Ryle play major roles in this story. This book also shows the connections among prominent astronomers like Oort, Minkowski, Baade, Struve, famous scientists in the UK such as J.A. Ratcliffe, Edward Appleton and Henry Tizard, and the engineers and physicists in Australia who helped develop the field of radio astronomy. Pawsey was appointed the second Director of the National Radio Astronomy Observatory (Green Bank, West Virginia) in October 1961; he died in Sydney at the age of 54 in late November 1962. Upper level students, scientists and historians will find the information, much of it from primary sources, relevant to any study of Joseph L. Pawsey or radio astronomy. This is an open access book

Australia Telescope Search for Cosmic Microwave Background Anisotropy

We have made an 8.7 GHz image of a sky region with a resolution of 8 arcmin and high brightness sensitivity using the Australia Telescope Compact Array (ATCA). in an ultra compact configuration. The foreground discrete-source confusion was estimated from observations with higher resolution at the same frequency and in a scaled array at a lower frequency. Following the subtraction of the foreground confusion, the field shows no features in excess of the instrument noise. This limits the CMB anisotropy flat-band power to Q_flat < 23.6 microK with 95 per cent confidence; the ATCA filter function F_l in multipole l-space peaks at l_eff = 4700 and has half maximum values at l = 3350 and 6050.Comment: Tex, 10 pages with 7 embedded figures, uses mn.tex accepted for publication in MNRA

The properties of extragalactic radio sources selected at 20 GHz

We present some first results on the variability, polarization and general properties of radio sources selected in a blind survey at 20 GHz, the highest frequency at which a sensitive radio survey has been carried out over a large area of sky. Sources with flux densities above 100 mJy in the AT20G Pilot Survey at declination -60 to -70 were observed at up to three epochs during 2002-4, including near-simultaneous measurements at 5, 8 and 18 GHz in 2003. Of the 173 sources detected, 65% are candidate QSOs, BL Lac objects or blazars, 20% galaxies and 15% faint (b > 22 mag) optical objects or blank fields. On a 1-2 year timescale, the general level of variability at 20 GHz appears to be low. For the 108 sources with good-quality measurements in both 2003 and 2004, the median variability index at 20 GHz was 6.9% and only five sources varied by more than 30% in flux density. Most sources in our sample show low levels of linear polarization (typically 1-5%), with a median fractional polarization of 2.3% at 20 GHz. There is a trend for fainter sources to show higher fractional polarization. At least 40% of sources selected at 20GHz have strong spectral curvature over the frequency range 1-20 GHz. We use a radio `two-colour diagram' to characterize the radio spectra of our sample, and confirm that the radio-source population at 20 GHz (which is also the foreground point-source population for CMB anisotropy experiments like WMAP and Planck) cannot be reliably predicted by extrapolating the results of surveys at lower frequencies. As a result, direct selection at 20 GHz appears to be a more efficient way of identifying 90 GHz phase calibrators for ALMA than the currently-proposed technique of extrapolation from all-sky surveys at 1-5 GHz.Comment: 14-page paper plus 5-page data table. Replaced with published versio

Comparison of the Parkes and FAST FRB DM distribution

We model the fast radio burst (FRB) dispersion measure (DM) distribution for the Five-hundred-meter Aperture Spherical Telescope (FAST) and compare this with the four FRBs published in the literature to date. We compare the DM distribution of Parkes and FAST, taking advantage of the similarity between their multibeam receivers. Notwithstanding the limited sample size, we observe a paucity of events at low DM for all evolutionary models considered, resulting in a sharp rise in the observed cumulative distribution function in the region of 1000 pc cm-3 ≲ DM ≲2000 pc cm-3. These traits could be due to statistical fluctuations (0.12 ≤ p ≤ 0.22), a complicated energy distribution or break in an energy distribution power law, spatial clustering, observational bias, or outliers in the sample (e.g. an excessive DMHost as recently found for FRB 20190520B). The energy distribution in this regime is unlikely to be adequately constrained until further events are detected. Modelling suggests that FAST may be well placed to discriminate between redshift evolutionary models and to probe the helium ionization signal of the intergalactic medium