S. Neuhold

Bio: S. Neuhold is an academic researcher from Australia Telescope National Facility. The author has contributed to research in topics: Fast radio burst & Redshift. The author has an hindex of 4, co-authored 5 publications receiving 319 citations. Previous affiliations of S. Neuhold include ASTRON.

A single fast radio burst localized to a massive galaxy at cosmological distance

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.

A single fast radio burst localized to a massive galaxy at cosmological distance

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.

ASKAP advancements in beamformer and correlator optical backplane technology

Abstract: The Australian Square Kilometre Array Pathfinder (ASKAP) is an array of 36-antennas located in Western Australia. Each antenna is outfitted with a 192-port phased array feeds (PAF) which targets wide field of view radio astronomy. Both PAFs and Correlators require backplanes to cross connect data inputs; in the case of a PAF its 192-ports into the Beamformer, and then for the Correlator its 36-antenna inputs. For ASKAP these digital cross connect communications require approximately 300Tbps - the aim is to do this as efficiently as possible (power, cabling, RFI and programming.). This paper explores existing solutions and also describes advancements in the second generation ASKAP hardware using optical backplane technology. These technology steps will become critical for SKA which will consist of many orders of magnitude more antennas than ASKAP, and may also potentially use PAF technology.

Australian SKA Pathfinder: Digital signal processing implementation and early engineering test array results

Abstract: The Boolardy Engineering Test Array (BETA) is the first prototype of the Australian Square Kilometer Array Pathfinder (ASKAP), a new radio telescope that is pioneering the use of Phased Array Feed (PAF) technology in radio astronomy to provide instantaneous wide field-ofview imaging. BETA consists of six 12 meter parabolic antennas, each equipped with a 188-element PAF at the focus and a signal processing system capable of imaging an instantaneous 7 square degree field-of-view with a bandwidth of 300MHz at a resolution of 18kHz. In this paper we describe the architecture of the digital signal processing chain and its implementation on reconfigurable hardware based on Field-Programmable Gate Array (FPGA) technology. We present early engineering results taken by the instrument during commissioning trials at the Murchison Radio Observatory (MRO) in remote Western Australia. In particular, we present the first multi-beam image of an astronomical source captured with a PAFbased interferometer.

A bright millisecond-duration radio burst from a Galactic magnetar

Abstract: Magnetars are highly magnetized young neutron stars that occasionally produce enormous bursts and flares of X-rays and gamma-rays. Of the approximately thirty magnetars currently known in our Galaxy and Magellanic Clouds, five have exhibited transient radio pulsations. Fast radio bursts (FRBs) are millisecond-duration bursts of radio waves arriving from cosmological distances. Some have been seen to repeat. A leading model for repeating FRBs is that they are extragalactic magnetars, powered by their intense magnetic fields. However, a challenge to this model has been that FRBs must have radio luminosities many orders of magnitude larger than those seen from known Galactic magnetars. Here we report the detection of an extremely intense radio burst from the Galactic magnetar SGR 1935+2154 using the Canadian Hydrogen Intensity Mapping Experiment (CHIME) FRB project. The fluence of this two-component bright radio burst and the estimated distance to SGR 1935+2154 together imply a 400-800 MHz burst energy of $\sim 3 \times 10^{34}$ erg, which is three orders of magnitude brighter than those of any radio-emitting magnetar detected thus far. Such a burst coming from a nearby galaxy would be indistinguishable from a typical FRB. This event thus bridges a large fraction of the radio energy gap between the population of Galactic magnetars and FRBs, strongly supporting the notion that magnetars are the origin of at least some FRBs.

A fast radio burst associated with a Galactic magnetar.

Abstract: Since their discovery in 20071, much effort has been devoted to uncovering the sources of the extragalactic, millisecond-duration fast radio bursts (FRBs)2. A class of neutron stars known as magnetars is a leading candidate source of FRBs3,4. Magnetars have surface magnetic fields in excess of 1014 gauss, the decay of which powers a range of high-energy phenomena5. Here we report observations of a millisecond-duration radio burst from the Galactic magnetar SGR 1935+2154, with a fluence of 1.5 ± 0.3 megajansky milliseconds. This event, FRB 200428 (ST 200428A), was detected on 28 April 2020 by the STARE2 radio array6 in the 1,281–1,468 megahertz band. The isotropic-equivalent energy released in FRB 200428 is 4 × 103 times greater than that of any radio pulse from the Crab pulsar—previously the source of the brightest Galactic radio bursts observed on similar timescales7. FRB 200428 is just 30 times less energetic than the weakest extragalactic FRB observed so far8, and is drawn from the same population as the observed FRB sample. The coincidence of FRB 200428 with an X-ray burst9–11 favours emission models that describe synchrotron masers or electromagnetic pulses powered by magnetar bursts and giant flares3,4,12,13. The discovery of FRB 200428 implies that active magnetars such as SGR 1935+2154 can produce FRBs at extragalactic distances. Observations of the fast radio burst FRB 200428 coinciding with X-rays from the Galactic magnetar SGR 1935+2154 indicate that active magnetars can produce fast radio bursts at extragalactic distances.

A repeating fast radio burst source localized to a nearby spiral galaxy

Abstract: Fast radio bursts (FRBs) are brief, bright, extragalactic radio flashes1,2. Their physical origin remains unknown, but dozens of possible models have been postulated3. Some FRB sources exhibit repeat bursts4–7. Although over a hundred FRB sources have been discovered8, only four have been localized and associated with a host galaxy9–12, and just one of these four is known to emit repeating FRBs9. The properties of the host galaxies, and the local environments of FRBs, could provide important clues about their physical origins. The first known repeating FRB, however, was localized to a low-metallicity, irregular dwarf galaxy, and the apparently non-repeating sources were localized to higher-metallicity, massive elliptical or star-forming galaxies, suggesting that perhaps the repeating and apparently non-repeating sources could have distinct physical origins. Here we report the precise localization of a second repeating FRB source6, FRB 180916.J0158+65, to a star-forming region in a nearby (redshift 0.0337 ± 0.0002) massive spiral galaxy, whose properties and proximity distinguish it from all known hosts. The lack of both a comparably luminous persistent radio counterpart and a high Faraday rotation measure6 further distinguish the local environment of FRB 180916.J0158+65 from that of the single previously localized repeating FRB source, FRB 121102. This suggests that repeating FRBs may have a wide range of luminosities, and originate from diverse host galaxies and local environments. Only one repeating fast radio burst has been localized, to an irregular dwarf galaxy; now another is found to come from a star-forming region of a nearby spiral galaxy.

A census of baryons in the Universe from localized fast radio bursts.

Abstract: More than three-quarters of the baryonic content of the Universe resides in a highly diffuse state that is difficult to detect, with only a small fraction directly observed in galaxies and galaxy clusters1,2. Censuses of the nearby Universe have used absorption line spectroscopy3,4 to observe the ‘invisible’ baryons, but these measurements rely on large and uncertain corrections and are insensitive to most of the Universe’s volume and probably most of its mass. In particular, quasar spectroscopy is sensitive either to the very small amounts of hydrogen that exist in the atomic state, or to highly ionized and enriched gas4–6 in denser regions near galaxies7. Other techniques to observe these invisible baryons also have limitations; Sunyaev–Zel’dovich analyses8,9 can provide evidence from gas within filamentary structures, and studies of X-ray emission are most sensitive to gas near galaxy clusters9,10. Here we report a measurement of the baryon content of the Universe using the dispersion of a sample of localized fast radio bursts; this technique determines the electron column density along each line of sight and accounts for every ionized baryon11–13. We augment the sample of reported arcsecond-localized14–18 fast radio bursts with four new localizations in host galaxies that have measured redshifts of 0.291, 0.118, 0.378 and 0.522. This completes a sample sufficiently large to account for dispersion variations along the lines of sight and in the host-galaxy environments11, and we derive a cosmic baryon density of $${\varOmega }_{{\rm{b}}}={0.051}_{-0.025}^{+0.021}{h}_{70}^{-1}$$ (95 per cent confidence; h70 = H0/(70 km s−1 Mpc−1) and H0 is Hubble’s constant). This independent measurement is consistent with values derived from the cosmic microwave background and from Big Bang nucleosynthesis19,20. The baryon density determined along the lines of sight to localized fast radio bursts is consistent with that determined from the cosmic microwave background and required by Big Bang nucleosynthesis.