Centre for Astronomy

Project Description: A number of ultra-cool dwarfs (the dimmest red dwarf stars and brown dwarfs, which are essentially “failed” stars) have been unexpectedly detected as radio sources in the last decade. Four of them produce strong periodic radio pulses. Our collaboration has now shown that several of these pulsing dwarfs are also periodically variable in optical photometry, and that the detected optical periods match the periods of the radio pulses, which have been associated with the short rotation periods of the dwarfs. Our development and extended usage of the GUFI (Galway Ultra Fast Imager) photometric camera on the 1.8m VATT telescope (Mt. Graham, Arizona) was the largest enabling factor in this breakthrough. For one dwarf, it was established that the optical and radio periodic variability are probably a consequence of magnetically-driven auroral processes. However, other causes (magnetic cool star-spots and atmospheric dust clouds) must also be considered. The student will conduct observing campaigns with GUFI , and analyse the photometric timeseries data (and re-analyse existing GUFI data) using newer "Optimum Aperture" & "Lucky Phot" techniques, in order to investigate the ubiquity, the stability (in both period and amplitude), and the cause(s) of the periodic optical variability in radio detected dwarfs.

Project Description: At present, the School of Physics/Centre for Astronomy operates the Imbusch Observatory on campus. This is a convenient location for undergrads and the public to get to – its main purposes are teaching and public outreach – but it is badly affected by urban light pollution. A dark-sky location somewhere in Connemara would be preferable for a second NUIG astronomical observatory. But choosing the best site is complex, with many constraints and metrics to consider – not just light pollution, but also financial, logistical, legal/planning, access, travel-time, a preference for altitude and an open aspect – and some of these constraints are actually in competition with each other. Obtaining accurate metrics data for our region (sky darkness etc.) will be a key component of this project. In parallel, the project will develop a tool to assign variable weights to these factors, combine, and colour-code the data by GIS (Geographical Information Systems) techniques as "heat" gradients on a map. Thus, the impact of different factors can be easily explored - the map will instantly regenerate from new weightings. The tool produced will be useful globally – users will simply assign their own locally-determined data, choose their weightings and generate maps for their own region.

Project Description: Globular star clusters are unique “labs in the sky”. The rich ecology of populations that we have studied in them includes several classes of variable stars (RR Lyrae, Type II Cepheids, Blue Stragglers), close binary stars, millisecond pulsars, and even an extra-solar planet. In pursuing these objects, we have developed parallel-processing deconvolution software, and shown that performing deconvolution of Hubble Space Telescope (HST) images yields more accurate detection and measurement (astrometry) of the stars in the crowded centres of the clusters, revealing milli-arcsecond motions of the stars over time. Meanwhile, precise image-matching methods have enabled us to photometrically discover and characterize new variable stars in globulars . This project will extend these methods to new targets, mining the HST archive to conduct a variability census in the most difficult and crowded cluster centres - where many new variable announcements have never been independently verified, and identifications/classifications have sometimes been ambiguous, so there is a need for a consistent, precise treatment on "known" variables - in addition to the scope for further new discoveries. Specific science goals include long-timebase monitoring for secular changes. Analysis will also be performed on simulated cluster images, to benchmark the techniques.

Project Description: The success of websites like DxOmark.com and DPreview.com shows that there is clearly a huge demand in the imaging/photography markets for independently produced sensor performance data. However, these sites tend to focus on relatively qualitative comparisons and unscientific test subjects, and they entirely neglect some key performance factors like long exposure dark noise, manipulation of bit depth, and the noise-skewing effects of internal bias subtraction in many camera models. This project will integrate methods for more rigorous characterization, through photon-transfer curves etc. Where data is zero-clipped (due to internal bias subtraction), new statistical methods will be developed for recovery of the noise measures. Working through the new industrial liaison officer for the College of Science, mutually beneficial partnerships will be forged with local suppliers for access to test/demo units, in return for good publicity and the kudos of academic-civic cooperation, which is a strategic goal of the university. Development of a mobile test rig would be the most effective way to quickly collect project data at supplier premises.

Project Description: Over a hundred astrophysical sources of Very-High-Energy gamma radiation (VHE, E>100GeV) are currently known, including nearby supernova remnants, and distant active galactic nuclei. Our research involves using the VERITAS telescope array (see veritas.sao.arizona.edu) to study these objects to help uncover how they produce radiation with such incredible energies. VHE gamma-rays observations can also be used to make more general measurements of the extragalactic background light, Lorentz invariance, and to search for dark matter. VHE gamma-rays produce cascades of relativistic electrons in the atmosphere and VERITAS can detect the very brief flashes (nanosecond) of optical Cherenkov light emitted by these cascades. Sophisticated multi-view image analysis techniques are used to reject a large background of charged cosmic ray initiated cascades. Sample MSc project: Observations of VHE gamma-ray emission from a nearby radio galaxy. This project involves the analysis of a large existing data base. Sample PhD project: Familiarisation with the VERITAS data analysis procedure; observations at the VERITAS site; participation in a major VERITAS science project such as constraining the extragalactic background light using VHE observations of AGN.

Project Description: The Atacama Large Millimetre Array (ALMA) in the Chilean desert has now begun operations. This is perhaps the largest ground based international scientific project of the decade. ALMA will revolutionise our ability to observe star and planet formation. High resolution molecular line data will reveal the innermost regions of star forming clouds for the first time. The principal aim of this research programme is to use our unique molecular line radiative transfer code (MOLecular LIne Explorer - MOLLIE) to characterise, model and reproduce ALMA molecular spectral line data from a wide variety of astrophysical sources, in particular star and planet forming molecular clouds and disks. MOLLIE will be used to model the rich and complex data that ALMA will produce. This will allow us to determine the physical conditions deep in these clouds and further our understanding of the star and planet formation process.

Project Description: The most massive stars are rare in number but disproportionately influential in the evolution of galaxies. Their winds, ultraviolet radiation fields and rapid evolution to supernovae greatly disturb the local environment, out of which thousands of low mass, sun-like stars will also be forming. These effects are mixed in that the sweep of shock waves on nearby molecular gas can trigger a new burst of star formation but can also disrupt individual star forming clouds or their protoplanetary disks. This project will investigate the process by which newly formed massive stars disrupt the thousands of low mass stars forming alongside them. The competing processes of ionization-led erosion and external pressure crushing on protostars will be modeled to estimate the amount of gas that will form a star and protoplanetary disk. The response of protostellar objects to the passage of a supernova blast wave will also be modelled. Depending on their evolutionary state, the shock could accelerate their collapse, disrupt their outer layers or even disperse them completely. At all stages, the models will be compared directly with observations, particularly from the new immense, globally funded, Atacama Large Millimetre Array (ALMA) that will examine the internal structure of star forming regions in unprecedented detail.

Project Description: The principal aim of this research programme is to comprehensively understand the peculiar emission properties of the HCN molecular spectrum, particularly when observed towards star forming clouds. The research will be to characterise, model and reproduce the HCN spectrum so as to allow this astronomical tracer species to be used to its full potential. The proposal is very timely since the first observations from the 1 billion dollar Atacama Large Millimetre Array (ALMA) in the Chilean desert are now well underway. This is perhaps the largest ground based international scientific project of the next decade and will revolutionise our ability to observe the star and planet formation process. HCN will be one of the key tracer species that will routinely used as an observational tool. This project will fully open up the HCN window on the universe allowing observations to be fully and correctly interpreted for the first time.

Project Description: Pulsars, rapidly rotating neutron stars, were first detected nearly fifty years ago. Since then, despite a wealth of observational material we still have no comprehensive picture for how they work. Understanding pulsar emission is important as it has both physics and astrophysics. For physics pulsars are environments for extremes – the highest known magnetic fields, strong gravity (and thus providing important tests of general relativity), very high energy plasmas. For astrophysics pulsars represent the end of a stars life and will help us understand the number of neutron stars and hence rate of type two supernovae. The Galway group has interests in a number of different areas of pulsar astrophysics all of which are suitable for a PhD project.

1. Optical observations of pulsars and pulsar systems using a combination of instruments ranging from our own GASP, the Padua group’s Iqueye instrument, BVIT on the South African Large telescope. These observations – primarily looking at the polarisation of the light from the pulsar - will be complemented by Hubble Space telescope and other observatory instruments to understand both the emission mechanism and the location of this emission within the pulsar’s magnetosphere.
2. Gamma ray observations of pulsars using the Fermi and Integral satellites. In particular we want to extend our work on gamma ray polarisation studies.
3. Continued development of our theoretical/computational programme looking at the development of particle-in-cell simulations of a pulsar’s plasma and/or the reverse engineering code to map the pulsars magnetosphere using polarisation observations.
4. Development of the GASP polarimeter – this will involve mainly optical design and construction of a new variant of the GASP polarimeter in particular to determine the absolute limitations of the 2-D division of amplitude polarimetry method.

All of these projects will involve collaborations with groups in France, Germany, Italy and Poland. Projects (1- 3) would be more straightforward for Physics with Astrophysics students although any good physics student could develop the necessary skills. Project 4 is suitable for Applied Physics and Physics with Astrophysics students.