Source Finding in the Era of the SKA (Precursors): Aegean 2.0

In the era of the SKA precursors, telescopes are producing deeper, larger images of the sky on increasingly small time-scales. The greater size and volume of images place an increased demand on the software that we use to create catalogues, and so our source finding algorithms need to evolve accordingly. In this paper, we discuss some of the logistical and technical challenges that result from the increased size and volume of images that are to be analysed, and demonstrate how the Aegean source finding package has evolved to address these challenges. In particular, we address the issues of source finding on spatially correlated data, and on images in which the background, noise, and point spread function vary across the sky. We also introduce the concept of forced or prioritised fitting

Low-Frequency Carbon Recombination Lines in the Orion Molecular Cloud Complex

We detail tentative detections of low-frequency carbon radio recombination lines from within the Orion molecular cloud complex observed at 99–129 MHz. These tentative detections include one alpha transition and one beta transition over three locations and are located within the diffuse regions of dust observed in the infrared at 100 µm, the Ha emission detected in the optical, and the synchrotron radiation observed in the radio. With these observations, we are able to study the radiation mechanism transition from collisionally pumped to radiatively pumped within the H ii regions within the Orion molecular cloud complex

A Molecular Line Survey around Orion at Low Frequencies with the MWA

The low-frequency sky may reveal some of the secrets yet to be discovered. Until recently, molecules had never been detected within interstellar clouds at frequencies below 700 MHz. Following the pilot survey toward the Galactic center at 103-133 MHz with the Murchison Widefield Array, we surveyed 400 deg2centered on the Orion KL nebula from 99 to 170 MHz. Orion is a nearby region of active star formation and known to be a chemically rich environment. In this paper, we present tentative detections of nitric oxide and its isotopologues, singularly deuterated formic acid, molecular oxygen, and several unidentified transitions. The three identified molecules are particularly interesting, as laboratory experiments have suggested that these molecules are precursors to the formation of amines

G17.8 + 16.7: A new supernova remnant

Non-thermal radio emission is detected in the region of the gamma-ray source FHES J1723.5 - 0501. The emission has an approximately circular shape 0.8° in diameter. The observations confirm its nature as a new supernova remnant, G 17.8 + 16.7. We derive constraints on the source parameters using the radio data and gamma-ray observations of the region. The distance to the object is possibly in the range 1.4-3.5 kpc. An SNR age of the order of 10 kyr is compatible with the radio and GeV features, but an older or younger SNR cannot be ruled out. A simple one-zone leptonic model naturally explains the multi-wavelength non-thermal fluxes of the source at its location outside the Galactic plane

Leading the spread and adoption of innovation at scale : an Academic Health Science Network's perspective

Background: There is virtually no limit to the number of innovations being developed, tested and piloted at any one time to improve the quality and safety of care. The perennial problem is spreading innovations that are proven to be effective on a smaller scale or under controlled conditions. Much of the literature on spread refers to the important role played by external agencies in supporting the spread of innovations. Academic Health Science Networks and the spread of innovation: External agencies can provide additional capacity and capabilities to adopter organisations, such as technical expertise, resources and tools to assist with operational issues. In England, the National Health Service (NHS) established 15 Academic Health Science Networks (AHSNs) to help accelerate the spread and adoption of innovation in healthcare. However, formal clinical-academic networks (such as AHSNs) themselves will not deliver positive, tangible outcomes on the ground (ie, evidence-based innovations embedded at scale across a system). This begs the question of how do AHSNs practically go about achieving this change successfully? We provide an AHSN’s perspective on how we conceptualise and undertake our work in leading implementation of innovation at scale. An AHSN's perspective: Our approach is a collaborative process of widening understanding of the innovation and its implementation. At its core, the implementation and spread of innovation into practice is a collective social process. Healthcare comprises complex adaptive systems, where contexts need to be negotiated for implementation to be successful. As AHSNs, we aim to lead this negotiation through facilitating knowledge exchange and production across the system to mobilise the resources and collective action necessary for achieving spread

Selecting and modelling remnant AGNs with limited spectral coverage

Quantifying the energetics and lifetimes of remnant radio-loud active galactic nuclei (AGNs) is much more challenging than for active sources due to the added complexity of accurately determining the time since the central black hole switched off. Independent spectral modelling of remnant lobes enables the derivation of the remnant ratio, Rrem (i.e. 'off-time/source age'); however, the requirement of high-frequency (≳5 GHz) coverage makes the application of this technique over large-area radio surveys difficult. In this work, we propose a new method, which relies on the observed brightness of backflow of Fanaroff-Riley type II lobes, combined with the Radio AGN in Semi-Analytic Environments (RAiSE) code, to measure the duration of the remnant phase. Sensitive radio observations of the remnant radio galaxy J2253-34 are obtained to provide a robust comparison of this technique with the canonical spectral analysis and modelling methods. We find that the remnant lifetimes modelled by each method are consistent; spectral modelling yields Rrem = 0.23 ± 0.02, compared to Rrem = 0.26 ± 0.02 from our new method. We examine the viability of applying our proposed technique to low-frequency radio surveys using mock radio source populations, and examine whether the technique is sensitive to any intrinsic properties of radio AGNs. Our results show that the technique can be used to robustly classify active and remnant populations, with the most confident predictions for the remnant ratio, and thus off-time, in the longest lived radio sources (>50 Myr) and those at higher redshifts (z > 0.1)

Discovery of a young, highly scattered pulsar PSR J1032-5804 with the Australian SKA Pathfinder

We report the discovery of a young, highly scattered pulsar in a search for highly circularly polarized radio sources as part of the Australian Square Kilometre Array Pathfinder (ASKAP) Variables and Slow Transients (VAST) survey. In follow-up observations with Murriyang/Parkes, we identified PSR J1032-5804 and measured a period of 78.7 ms, dispersion measure (DM) of 819$\pm$4 pc cm$^{-3}$, rotation measure of -2000$\pm$1 rad m$^{-2}$, and a characteristic age of 34.6 kyr. We found a pulse scattering timescale at 3 GHz of ~22 ms, implying a timescale at 1 GHz of ~3845 ms, which is the third most scattered pulsar known and explains its non-detection in previous pulsar surveys. We discuss the identification of a possible pulsar wind nebula and supernova remnant in the pulsar's local environment by analyzing the pulsar spectral energy distribution and the surrounding extended emission from multiwavelength images. Our result highlights the possibility of identifying extremely scattered pulsars from radio continuum images. Ongoing and future large-scale radio continuum surveys will offer us an unprecedented opportunity to find more extreme pulsars (e.g., highly scattered, highly intermittent, highly accelerated), which will enhance our understanding of the characteristics of pulsars and the interstellar medium.Comment: 15 pages, 10 figures, 2 tables. Accepted for publication in Ap