Since 2009, ICRAR’s scientists have made valuable discoveries and advancements to techniques for studying the Universe. These achievements have played a key part in our rapid growth into an internationally-renowned centre of astronomy research. The following recent highlights are extracted from a recent Annual Report.
Galaxy Assembly and Evolution
SoFiA – A new neutral hydrogen detection tool
ICRAR scientists, Tobias Westmeier, Martin Meyer and Attila Popping, with CSIRO collaborators, developed a new tool for detecting hydrogen in galaxies, which will be integrated with the WALLABY (ASKAP) survey of half a million galaxies. Hydrogen comprises roughly 90% of the Universe’s non-dark matter material and therefore is a reliable indicator of mass within galaxies. SoFiA is a neutral hydrogen source finding and parameterisation pipeline that combines all the algorithms created within the group over the last few years, including wavelet denoising, spatial and spectral smoothing and spectral profile fitting.
Discovery of young galaxy groups through H-alpha emissions
The SINGG (Survey of Ionisation in Neutral Gas Galaxies) team, led by Professor Gerhardt Meurer, discovered that 15 previously identified sources are, in fact, groups of four or more galaxies rather than individual galaxies. The SINGG team used H-alpha emission (a spectral line of hydrogen) observations from the set of Parkes neutral hydrogen (HI) sources to distinguish the galaxies. Since H-alpha is an indicator of young stars and star formation, this finding is noteworthy because groups of galaxies are usually gas poor and have few young, star forming galaxies. This work demonstrated the usefulness of using H-alpha observations with neutral hydrogen (HI) detections as a technique for identifying groups of young galaxies.
New stacking technique to improve neutral hydrogen maps
A new technique of combining hydrogen signals from distant galaxies was developed by ICRAR PhD graduate Jacinta Delhaize. The spectral stacking technique provides a more comprehensive map of neutral hydrogen in the Universe, the most abundant non-dark matter material in the Universe. More complete neutral hydrogen studies will improve galaxy mapping, and our understanding of their formation and evolution, thereby guiding and amplifying the value of future telescope surveys, including the SKA.
Mapping of the Universe’s filamentary structure, the discovery of cosmic tendrils and the two-phase evolution of galaxies
The multi-wavelength GAMA survey, led by ICRAR Professor Simon Driver, has made several outstanding advancements in understanding the nearby Universe. The survey combines several ground and space-based telescope observations to create unprecedented coverage of the electromagnetic spectrum. Due to the broad range of wavelengths emitted by cosmic processes, GAMA has formed a more comprehensive view of the Universe, including mapping its filamentary structure, the discovery of tendrils – short strings of faint galaxies previously thought to be empty space, and the discovery that galaxies have evolved through two distinct phases – a “hot” rapid collapse phase and a lengthy “cold” infall phase.
Validation and refinement of dark matter models
The Computational Theory group has been instrumental in shedding light on the distribution and nature of dark matter. The group confirmed the most statistically robust method for testing dark matter models and found that gravitational forces between satellite galaxies and dark matter substructures are more common in Cold Dark Matter (CDM) models than Warm Dark Matter (WDM) models. PhD candidate Steven Murray, Dr Chris Power & Dr Aaron Robotham developed a python package and web application for calculating the dark matter halo mass function in common cosmologies, and used it to conclude that that the key uncertainty in the function arises from uncertainties in the fitting functions and not the cosmological parameters employed.
Evidence that current galaxy morphologies and content is strongly dependent on star formation rate in the early Universe
Galaxy formation simulations by Dr Chris Power and his team showed that the star formation rate in the early Universe played an important role in the suite of galaxy morphologies and gas content of the Universe today. Predictions of the detectability of the gaseous cosmic web for ASKAP, MWA and the SKA have been made by ICRAR collaborators using cosmological hydrodynamical simulations which will be important for guiding and validating these surveys. A mapping that will allow diffuse emission from the cosmic web to be included in future galaxy catalogues has also been developed.
Leader in the search for Fast Radio Bursts and detection of refractive and scintillation effects in the interstellar medium
ICRAR have been a major participant in the international race to detect and localise a Fast Radio Burst – a millisecond pulse of emission – one of this decade’s most significant radio astronomy challenges. The first fast radio burst was detected in “real-time” (the detected burst happened billions of years ago but was so far away that the emission only just reached Earth!) in 2014 by a PhD student with the Parkes radio telescope. With its high time-resolution, sensitivity and field of view, the MWA is primed to detect several more fast radio bursts and give valuable insight into extremely distant and energetic cosmic events.
The MWA recently detected and made the lowest-frequency scintillation studies of pulsar, PSR J0437-4715, which is important in high-precision timing with applications to the detection of gravitational waves. The study has identified signatures from diffractive and refractive scintillation effects in the interstellar medium (ISM).
Several existing Gamma Ray Burst (GRB) emission mechanism theories dismissed by discovery of anomalous properties from a GRB
ICRAR research fellow Dr Peter Curran was part of a team that observed anomalous properties from one of the Universe’s most energetic events. Gamma-Ray Burst (GRB) 121024A was found to emit radiation 1000 times more polarised (oriented in a single direction) than expected from the dying star’s collapse into a black hole. This finding rules out many existing theories of GRB emission mechanisms and also points to some new ones.
First discovery of radio jet emissions from a stellar-mass black hole outside our galaxy
A team of ICRAR researchers discovered radio jet emissions from a black hole only 10 times the mass of our Sun consuming matter at an excessively high rate. ICRAR researchers Dr James Miller-Jones, Dr Natasha Hurley-Walker, Dr Jean-Pierre Macquart and Dr John Morgan used a range of telescopes to study the relationship between X-ray and radio emission from the black hole of a newly discovered Ultraluminous X-Ray Source (ULX) in our neighbouring galaxy, Andromeda. Their study concluded the source was a stellar-mass black hole feeding at an abnormally fast rate and was the first time radio jet emissions had been detected from a stellar-mass black hole outside our galaxy.
High angular resolution radio astronomy
First publications from SKA-precursor, ASKAP, and first demonstration of optical fibre link between MRO and Perth
The High Angular Resolution Radio Astronomy group assisted the first publications from ASKAP and AuScope (a geodesy and astronomy radio telescope array in Tasmania, Western Australia and the Northern Territory) and the first demonstration of the optical fibre link between the Murchison Radio-astronomy Observatory and Perth. The group also produced six wide-field Very Long Baseline Interferometry (VLBI) publications demonstrating the enhanced capability of wide-field VLBI. One of these publications presented improved imaging and estimates of star formation and supernova rates in starburst galaxy, NGC 253.