The ATLAS-SPT radio survey of cluster galaxies

Using a high-performance computing cluster to mosaic 4,787 pointings, we have imaged the 100 sq. deg. South Pole Telescope (SPT) deep-field at 2.1 GHz using the Australian Telescope Compact Array to an rms of 80 mJy and a resolution of 8". Our goal is to generate an independent sample of radio-selected galaxy clusters to study how the radio properties compare with cluster properties at other wavelengths, over a wide range of redshifts in order to construct a timeline of their evolution out to z ~ 1:3. A preliminary analysis of the source catalogue suggests there is no spatial correlation between the clusters identified in the SPT-SZ catalogue and our wide-angle tail galaxies

Real-time event-based unsupervised feature consolidation and tracking for space situational awareness

Earth orbit is a limited natural resource that hosts a vast range of vital space-based systems that support the international community's national, commercial and defence interests. This resource is rapidly becoming depleted with over-crowding in high demand orbital slots and a growing presence of space debris. We propose the Fast Iterative Extraction of Salient targets for Tracking Asynchronously (FIESTA) algorithm as a robust, real-time and reactive approach to optical Space Situational Awareness (SSA) using Event-Based Cameras (EBCs) to detect, localize, and track Resident Space Objects (RSOs) accurately and timely. We address the challenges of the asynchronous nature and high temporal resolution output of the EBC accurately, unsupervised and with few tune-able parameters using concepts established in the neuromorphic and conventional tracking literature. We show this algorithm is capable of highly accurate in-frame RSO velocity estimation and average sub-pixel localization in a simulated test environment to distinguish the capabilities of the EBC and optical setup from the proposed tracking system. This work is a fundamental step toward accurate end-to-end real-time optical event-based SSA, and developing the foundation for robust closed-form tracking evaluated using standardized tracking metrics

Odin observations of H2O in the Galactic Centre

The Odin satellite has been used to detect emission and absorption in the 557-GHz H2O line in the Galactic Centre towards the Sgr A* Circumnuclear Disk (CND), and the Sgr A +20 km/s and +50 km/s molecular clouds. Strong broad H2O emission lines have been detected in all three objects. Narrow H2O absorption lines are present at all three positions and originate along the lines of sight in the 3-kpc Spiral Arm, the -30 km/s Spiral Arm and the Local Sgr Spiral Arm. Broad H2O absorption lines near -130 km/s are also observed, originating in the Expanding Molecular Ring. A new molecular feature (the ``High Positive Velocity Gas'' - HPVG) has been identified in the positive velocity range of ~ +120 to +220 km/s, seen definitely in absorption against the stronger dust continuum emission from the +20 km/s and +50 km/s clouds and possibly in emission towards the position of Sgr A* CND. The 548-GHz H2_18O isotope line towards the CND is not detected at the 0.02 K (rms) level.Comment: 5 pages, 3 figures, accepted by A&A, special Odin Letters issu

Understanding the origin and impact of relativistic cosmic particles with very-high-energy gamma-rays

This white paper briefly summarizes the importance of the study of relativistic cosmic rays, both as a constituent of our Universe, and through their impact on stellar and galactic evolution. The focus is on what can be learned over the coming decade through ground-based gamma-ray observations over the 20 GeV to 300 TeV range

A deep spectromorphological study of the γ -ray emission surrounding the young massive stellar cluster Westerlund 1

Context. Young massive stellar clusters are extreme environments and potentially provide the means for efficient particle acceleration. Indeed, they are increasingly considered as being responsible for a significant fraction of cosmic rays (CRs) that are accelerated within the Milky Way. Westerlund 1, the most massive known young stellar cluster in our Galaxy, is a prime candidate for studying this hypothesis. While the very-high-energy γ-ray source HESS J1646-458 has been detected in the vicinity of Westerlund 1 in the past, its association could not be firmly identified. Aims. We aim to identify the physical processes responsible for the γ-ray emission around Westerlund 1 and thus to understand the role of massive stellar clusters in the acceleration of Galactic CRs better. Methods. Using 164 h of data recorded with the High Energy Stereoscopic System (H.E.S.S.), we carried out a deep spectromorphological study of the γ-ray emission of HESS J1646-458. We furthermore employed H I and CO observations of the region to infer the presence of gas that could serve as target material for interactions of accelerated CRs. Results. We detected large-scale (~2 diameter) γ-ray emission with a complex morphology, exhibiting a shell-like structure and showing no significant variation with γ-ray energy. The combined energy spectrum of the emission extends to several tens of TeV, and it is uniform across the entire source region. We did not find a clear correlation of the γ-ray emission with gas clouds as identified through H I and CO observations. Conclusions. We conclude that, of the known objects within the region, only Westerlund 1 can explain the majority of the γ-ray emission. Several CR acceleration sites and mechanisms are conceivable and discussed in detail. While it seems clear that Westerlund 1 acts as a powerful particle accelerator, no firm conclusions on the contribution of massive stellar clusters to the flux of Galactic CRs in general can be drawn at this point

AST/RO : lessons from a decade of sub-mm astronomy at the South Pole

AST/RO spent over a decade at the South Pole, observing submillimetre-wave emission from the interstellar medium. We outline some of the lessons learned and experience gained that may be relevant to future Antarctic projects. Small submillimetre-wave telescopes, on the excellent sites provided by the Antarctic plateau, have very strong large-area mapping capabilities, together with the potential for ground-based THz observations. Highlighted technical aspects include AST/RO’s lack of icing problems and availability of warm space

Gas temperatures in Orion B North

We present observations of two formaldehyde transitions towards 14 clumps in the Orion B North complex; the ratio of these transitions is an indicator of the kinetic temperature of the molecular gas. The spectra show narrow-line components with temperatures 20–30 K, and broader components with rather higher temperatures

Multimessenger Astronomy in Practice

The first non-electromagnetic messengers from space were discovered in the early 20th century, but it is only now that multimessenger astronomy is coming into its own. The aim of Multimessenger Astronomy in Practice is to aid an astronomer who is new to research in a particular area of multimessenger astronomy. Covering electromatic radiation from radio through to gamma-rays, and moving on to neutrino, cosmic-ray and gravitational wave astronomy, it gives the reader an overview of the celestial objects detected in each region, the unique methods used to measure them, as well as the principles and methods of data collection, calibration, reduction and analysis. Further chapters cover dark matter, the multimessenger search for extraterrestrial intelligence (SETI), and data science with machine learning. The book will help educate astronomy students taking a multimessenger approach, and add to the knowledge of professional astronomers about what is available in today's multimessenger toolbox

Principles of Multimessenger Astronomy

Astronomy has traditionally relied on capturing photons from cosmic sources to be able to understand the universe. During the 20th and 21st centuries, different messengers have been added to the astronomer's toolset: cosmic rays, neutrinos, and most recently gravitational waves. Each of these messengers opens a new window on the universe, and a modern astronomer must be familiar with them. The goal of this book is to provide a broad understanding of these messengers and their relationship to each other. The unique physics of each messenger is introduced, as well as the physics of their detection and interpretation. An additional focus is the discussion of techniques and topics that are common to more than one messenger. Principles of Multimessenger Astronomy is designed to be both an introduction and reference to modern astronomy

Astrophysics from Antarctica: Proceedings of the 288th Symposium of the International Astronomical Union held in Beijing, China, August 20-24, 2012

The remarkable environment of Antarctica offers many advantages for astronomical observations. Over the past two decades this field of scientific endeavour has developed dramatically and Antarctic-based observatories now regularly contribute to front line astrophysical research. This volume presents the Proceedings from the first ever International Astronomical Union Symposium to be held on the subject. After describing our knowledge of the special environment for Antarctic astronomy, it covers the following principal science areas: measuring the cosmic microwave background radiation; neutrino detection; cosmogenic signatures from the ice and atmosphere; submillimetre and terahertz astronomy; and optical and infrared astronomy. Each topic begins with reviews covering the field and the science being undertaken in it, followed by descriptions of the experiments, the telescopes and the results obtained. Another special feature surveys Antarctic stations and the astronomical facilities they contain. The volume concludes by considering the future for astronomical research in Antarctica