Research

Savilian Professor of Astronomy: Professor Joe Silk

Philip Wetton Professor of Astrophysics & Chair of Oxford Physics: Professor Roger Davies

Head of Astrophysics: Professor Steve Rawlings

Research at Oxford spans a wide range of astronomy and astrophysics, from the largest scales in the Universe to observational work on stars and the interstellar medium. Astrophysics research is carried out in two sub-departments of physics: Astrophysics and Theoretical physics. There are good opportunities for graduate students studying for the D.Phil research degree (equivalent to Ph.D.). Applications for graduate study in astrophysics are considered jointly by the two sub-departments. Both sub-departments are situated close to each other on the Keble Road site, close to the centre of Oxford and the University Parks.

Oxford Astrophysics has been successful in attracting long-term Royal Society, PPARC Advanced and other Senior Research Fellows funded by a grant from the Leverhulme Trust. PPARC grants support research into cosmology and extragalactic astrophysics, theoretical cosmology and in astronomical instrumentation. We are taking a major role in the construction of the UK-Japan near-infrared, fibre-fed, multi-object spectrograph, FMOS, for the 8m Subaru telescope. Oxford is also a partner in consortia designing and building second generation instruments for the European Southern Observatory's VLT and the Gemini telescopes, notably KMOS, MUSE, WFMOS and ExAOC. We have also won a Marie Curie Excellence Grant from the European Commission for realising SWIFT, a novel integral field spectrograph. Oxford was the coordinating node for CMBNET, a European network for collaborative research into the cosmic microwave background, and for the Early Universe European network for particle cosmology. Oxford also is a node in the European networks on Type Ia Supernovae (theory and observation).

Oxford astrophysicists are very successful in gaining observing time on observing facilities, including 8m class telescopes ( Gemini, Subaru, and VLT) and the Hubble Space Telescope for optical and infrared observations, as well as facilities spanning the electromagnetic spectrum from X-ray ( XMM-Newton), far-infrared (Spitzer), sub-millimetre (JCMT) through to radio (VLA) wavelengths. The UK Gemini Support Group is located at Oxford. In theoretical astrophysics, there are strong programmes in the area of galaxy dynamics, cosmology, galaxy formation, dark matter and the cosmic microwave background radiation. The appointment of Professor Roger Davies has led to an expansion in astronomical instrumentation.

1. Observational cosmology and galaxies

M Bureau, K Blundell, G Cotter, G Dalton, R Davies, I Hook, R Johnson, L Miller, S Rawlings, N Thatte.

1.1 Introduction

Theory provides predictions of the spectrum of fluctuations in the matter distribution of the Universe, but testing these predictions by making observations is by no means straightforward. The matter fluctuations may be traced by making surveys of galaxies, clusters of galaxies, quasars or radio sources. Determination of the three-dimensional structure of the Universe requires surveys covering a large fraction of the observable Universe, and these surveys must account for a variety of biases and projection effects. Problems encountered range from those that are conceptually simple but observationally challenging - such as the requirement of redshift information for a large number of objects - to those that are subtle such as the distortions due to gravitational lensing of distant objects by the intervening matter distribution. At Oxford we are, for example, studying the structure of the Universe using Type Ia Supernovae. The present paradigm for galaxy formation and evolution has galaxies assembling in their dark matter halos as these merge to form ever more massive objects over cosmic time. The Hubble Space Telescope (HST) has shown us that galaxy interactions and mergers were more common in the distant past and that these events are frequently associated with star formation episodes. How the luminous components of galaxies come to have their present appearance, why some have disks and others do not and when the major star forming episodes occurred are some of the central goals of our observational work on galaxy evolution. In addition to using normal and active galaxies as cosmological probes, there are a number of programmes at Oxford which aim to improve our understanding of how active galaxies work. Key questions include: why do only some active galaxies develop powerful radio-emission; what is the link between extranuclear star formation and nuclear activity; is there a link between the mass and structure of the host galaxy and the type of nuclear activity; why were there large changes in the space density of active galaxies with cosmic time? These programmes require observations at all wavebands, and often at the high angular resolution offered by Very Long Baseline Interferometry at radio wavelengths or the HST in the infrared, optical and ultraviolet wavebands.

1.1.1 New galaxy surveys

Our group is working on a number of surveys of large-scale structure as traced by galaxies and clusters of galaxies, both nearby and distant. The aim of this research is to study the formation and evolution of galaxies and their large-scale distribution. One of these surveys used the two-degree field (2dF) facility at the Anglo-Australian Telescope, which allows simultaneous measurement of the spectra of several hundred galaxies over that field. The Anglo-Australian 2dF Redshift Survey measured redshifts for 250,000 galaxies; this provided the first three-dimensional measurements of galaxy clustering on the large scales that may be studied at early cosmic epochs by measuring fluctuations in the microwave background. As we probe the galaxy distribution to fainter magnitude limits, the study of galaxy clustering is affected by the evolutionary histories of the galaxies themselves, as we see more distant objects at earlier times. The combined effects of cosmological redshift and galaxy evolution imply that multicolour surveys of faint galaxies are required to trace the evolution of galaxy clustering. We are in the process of constructing a deep wide-field optical and infra-red survey of faint galaxies. This will be used to identify candidate clusters of galaxies at a range of cosmological epochs, which will be followed up using the new generation of 8-m. telescopes to study the evolution of galaxies and galaxy clustering.

Local galaxies can be studied with greater precision and linear resolution than high redshift galaxies allowing us to make connections between their structure, dynamics and star-formation history. Our work seeks to characterise and model local galaxies as a function of luminosity, environment and Hubble type. In this work we apply the latest instrumental techniques that allow us to take a spectrum at every point in a galaxy simultaneously (using Integral Field Spectrographs, IFS) to produce a map of the velocity field and composition of the gas and stars. We are also able to estimate the age of the stars that dominate the integrated light. A few galaxies have core regions with stellar kinematics that are completely decoupled from those of the rest of the galaxy and this is taken as an indication of a past merger, but when did it occur? NGC4365, shown in the figure, is a good example.

SAURON data on the galaxy NGC 4365.

The velocity map shows that, this otherwise ordinary galaxy is rolling around its long axis but the central regions are rotating roughly perpendicular to this! The lower right panel shows that the strength of the H-beta Balmer absorption line is constant across the entire galaxy, both the decoupled core and main body. This shows that the stars in both components are the same age. It is very likely that the decoupled kinematics arose from a merger but character of the stars tells us this happened 12-14 Gyrs ago in the initial star forming event and that the galaxy has been quiescent since. The core is a remnant of the formation process, not the result of a late merger. Thus by measuring both the kinematics and the ages of the stellar population we are able to deduce the evolutionary history of galaxies. That work used the purpose built SAURON spectrograph on the William Herschel Telescope with which we are pursuing an extensive survey. We plan to use IFS on the 8m Gemini and VLT telescopes to extend this work to higher redshift galaxies and into the infrared allowing us to "age" and "weigh" distant galaxies to test the assembly paradigm directly. Through this work we have developed precise techniques for determining the mass-to-light ratio of galaxies, their ages and compositions all of which can be adapted to measure the evolution of galaxies directly by studying the galaxy population in groups and clusters at high redshift. We know that the galaxy population in dense regions of the universe is quite different from that in regions of average density but we do not know why. Through statistical studies of galaxies in different environments over a range of redshift we can eliminate candidate mechanisms. We use the luminosity in X-rays to signal the presence of a true physical association at high redshift and to determine the local density of the intergalactic medium. By using multiple object spectroscopy at both optical and infrared wavelengths we can assemble large galaxy samples for this work.

Further information - Martin Bureau & SAURON

1.1.8 Measuring the effects of Dark Energy using type Ia Supernovae

The use of Type Ia supernovae as standard candles has provided evidence that the expansion of the Universe is accelerating. Work is now underway to understand the nature of the mysterious "Dark Energy" driving this acceleration. To do this involves collecting an unprecendented sample of high-redshift supernova with better quality photometric and spectroscopic data. Researchers in Oxford are working in collaboration with colleagues around the world on major surveys, in particular the Supernova Legacy Survey to find and study distant supernovae, using the world's leading observational facilities. Recently we have been looking at the details of the spectra of distant supernovae and comparing them with their nearby counterparts, in order to search for possible signs of evolution in the population. This is an important test because the use of Type Ia supernovae for cosmology hinges on the assumption that the populations are similar and that Type Ia supernovae can be calibrated as "standard candles" out to redshifts of around one.

Further information - Isobel Hook

Type Ia supernova SN 1994D in the galaxy NGC 4526, observed by the HST.

2. Theoretical extragalactic astrophysics and cosmology

J Binney*, S Kay, S Khochfar, J Magorrian*, P Ferreira, J Silk

This group's research concerns the dynamics under gravity of all astrophysical systems that are not extremely relativistic. It includes the formation of large scale structure in the Universe, the formation of galaxies, galaxy evolution, the dynamics of the Milky Way and other galaxies, gravitational lensing and the long term evolution of the Solar System. Much of this research is driven by observations from the new generation of telescopes and instruments, including the HST and preparation for future missions, such as ALMA, PLANCK, NGST, and the new generation of cosmic microwave background experiments. The modelling involves both analytical and numerical work, with modern theories of non-linear dynamics playing a unifying role.

2.1 The cosmic microwave background

The origin of large-scale structure may be probed by studying trace fluctuations in the cosmic microwave background. These are imprinted by primordial irregularities in density that grew by gravitational instability in the early Universe. The increasingly refined measurements of anisotropies that have been detected over a range of angular scales are beginning to constrain and even challenge theoretical models. Planned radio and submillimetre wavelength experiments using telescopes on balloons (the recent BOOMERANG experiments), satellites (MAP in 2001- and Planck from 2007) and ground-based interferometer arrays will approach a level of sensitivity that will definitively measure many, if not all, cosmological parameters with unprecedented precision. One of the major uncertainties is that of foregrounds, both galactic and extragalactic, which need to be evaluated in order to enhance the precision of such measurements. Simulations of sky maps will be one of the activities that will be undertaken at Oxford. In a complementary attack on large-scale structure, the deep galaxy redshift surveys now underway and which will obtain of order a million redshifts have the sensitivity to probe large-scale power in density fluctuations in the nearby Universe. The physical scales that are studied in this way overlap with the power spectrum inferred at high redshift from mapping of the cosmic microwave background, and combination of the two approaches will provide new insights into models for large-scale structure. On small angular scales, early formation of galaxy clusters, radio galaxies and quasars inevitably provide energy input into the intergalactic medium and generate fine- scale temperature anisotropies. Understanding the detailed nature of such signatures will help define a goal for new generations of experiments and satellite missions.

2.2 Galaxy formation

Understanding how galaxies form and unravelling the nature of the origin of the large-scale structure of the Universe are key unresolved issues in cosmology. A focus of our research includes the study of galaxy formation and evolution. The challenge of galaxy formation theory is to account for the fossilised properties of galaxies, such as morphologies, scaling relations, and chemical abundances, as well as the evolution of these properties with redshift. The star formation histories of disk and elliptical galaxies and their high redshift counterparts provide vital clues to galactic evolution. Semi-analytical techniques can be applied to yield global star formation rates in disk galaxies and evolve nearby galaxies backwards in time. Galaxy mergers induce ultraluminous starbursts, and study of such phenomena, including the roles of infall, galactic winds and active nuclei, provides insight into spheroid formation. An improved understanding of protogalaxy evolution will have profound implications for understanding chemical evolution and for interpreting far infrared and submillimetre observations of star- forming galaxies in the distant Universe.

2.3 Dark matter

The frontier of particle physics is beyond the TeV energy range of current generations of accelerators but in the realm of the energy scales of supersymmetry or grand unification, or even quantum gravity. The interface of cosmology and particle physics plays a critical role in motivating such research. These seemingly diverse realms coincide in the Big Bang cosmology, which provides a unique particle accelerator that operates up to energies of 1019 GeV. The study of the early Universe thus provides a unique laboratory for searching for relics from very early epochs for testing ideas from such theories as grand unification and supergravity. Perhaps the most important development has been that of the inflationary cosmology, which may solve a number of outstanding problems that have puzzled cosmologists for over half a century. These include the isotropy of the Universe, its size, its homogeneity on large scales and its lack of homogeneity on small scales, and the paucity of bizarre relics such as monopoles. Predictions of inflationary cosmology, such as the origin and spectrum of density fluctuations and the distribution and composition of dark matter, are important to the understanding of galaxy formation and sensitively depend on the details of the correct particle theory. The particle relics from the beginning of the Universe may surround us today in the form of dark matter in galaxy halos. One current study explores the hypothesis that the dark matter in our galactic halo and in the halos of nearby galaxies consists of massive stable relic particles which occasionally annihilate to produce a substantial flux of sub-GeV cosmic ray antiprotons, high energy gamma-rays and neutrinos with unique spectral signatures.

2.4 Galaxy dynamics

Having used Sauron or a similar instrument to obtain a kinematical map of a galaxy, what does the map tell us about the galaxy's mass distribution? This question is surprisingly difficult to answer, even for the simplest case of a perfectly spherical galaxy. Nowadays the standard way to attack it is by using an extension of Schwarzschild's orbit-superposition method. Much of the focus at Oxford, however, has been on developing a more powerful scheme that makes use of the fact that, when viewed in action-angle co-ordinates, stellar motions are particularly simple, with the stars moving on three-dimensional tori. Action-angle variables are the natural starting points for perturbation theory. Over the last decade the Oxford Torus Project has been developing the tools necessary to apply these ideas to the construction of detailed models of real galaxies. In addition, we also work on applications and refinements of the more traditional Schwarzschild method.

One of the more striking results to have come out of these and other models is that most reasonably large galaxies harbour so-called `supermassive' black holes at their centres. In addtion to our work on black hole demographics, we also carry out more theoretical investigations into the effects these black holes have on their host galaxies. For example, how do single and multiple black holes affect the distribution of stars in the surrounding bulge? When two galaxies merge, do their black holes merge too? Our work on these problems involves N-body simulation as well as more analytical approaches.

Further information

2.5 The Milky Way

The Oxford workers are engaged in a long term project towards a comprehensive understanding of the Milky Way. Over the last decade, Binney and co-workers have been developing a new method (the Oxford Torus Project) to analyse the stellar kinematics of nearby stars. When stellar motion is viewed in a six-dimensional phase space of positions and momenta, it is particularly simple. The stars move on three-dimensional tori. This feature is preserved under slow adiabatic perturbations. By adjusting the distributions of stars on tori, models are obtained for the interpretation of the kinematics of stars in the Milky Way. Another area undergoing rapid development is the study of the Bulge of the Milky Way. The DIRBE instrument that flew on the COBE satellite provided the most detailed picture to date of the Galactic Bulge. This is evidently asymmetric; for example, the infrared light distribution is brighter towards positive longitudes than negative longitudes. This was striking confirmation of a viewpoint earlier advanced in Oxford and elsewhere that the Milky Way galaxy is barred, with the near-side of the bar lying towards positive longitudes. A major effort (the Oxford Bar Project) aims at developing a series of stellar dynamical models of the inner Galaxy and using them to interpret the radial velocity and proper motion data towards the Galactic Centre. The microlensing surveys are a very new and important source of information on the Milky Way. So far the dynamical implications for our galaxy are not well understood, and Binney has been in the forefront of the struggle to understand these data using models developed both for the dark halo and the Bulge.

3. Stellar Astrophysics

J Bell-Burnell, S Justham, A Lynas-Gray, J Miller, P Podsiadlowski.

3.1 Theoretical stellar astophysics: the evolution of single and binary stars

Two of the major areas of stellar research involve the study of the late evolution of stars leading to supernova explosions and the modelling of binaries, in particular those containing compact objects. One major objective is to understand the origin of the diversity of observed supernovae, the role various factors such as binarity, metallicity and rotation play and their implications for galaxy evolution models. This includes Type Ia supernovae which have been used as important cosmological distance candles despite the fact that the physics of these explosions are yet poorly understood. Similarly, very little is presently known about the progenitors and the central engine of gamma-ray bursts, the largest explosions in the Universe. In the area of compact binary evolution, we are particularly interested in studying the evolution of low- and intermediate-mass X-ray binaries and their relation ot millisecond pulsars, and binaries containing black holes and their possible relation to ultraluminous X-ray sources in external galaxies. We also attempt to understand the physics of stars, including the Sun, through the technique of astero- and helioseismology.

Further information

3.1.1 Supernovae

There are two fundamentally different types of supernovae: thermonuclear explosions which occur when a white dwarf is pushed above its maximum mass of 1.4 solar masses (the Chandrasekhar limit) and which leads to the complete disruption of the star (referred to as a ÔType Ia supernovaÕ), and core-collapse supernovae which take place when the core of a massive star has exhausted all of its nuclear fuel. In the latter case, the core of the star collapses to leave a compact remnant, a neutron star or in some cases a black hole. A small fraction of the energy released in the collapse is deposited in the envelope, leading to an explosion and the bright, spectacular display we refer to as a supernova. The appearance of the supernova, however, depends sensitively on the pre-supernova structure of the envelope and hence the starÕs evolutionary history in a binary. The various binary interactions (mass loss, mass accretion and merging) can fundamentally change the structure of a massive star and may thereby account for many of the observational supernova sub-classes.

We are particularly interested in applying this theory to two of the most interesting nearby supernovae of our generation, SN 1987A and SN 1993J. SN 1987A was the first naked-eye supernova since KeplerÕs supernova in 1604 and is a highly anomalous supernova. Contrary to what had been predicted, the progenitor was a blue supergiant instead of a red supergiant, and is surrounded by a spectacular, but very complex, nebula consisting of three bright rings (seen most clearly with recent HST images) and has various chemical anomalies in its envelope. At the moment, these anomalies can be best explained if the progenitor originally was in a binary and has merged with its companion in the not-too-distant past. We are actively modelling all the detailed physical processes involved in the merging of two massive stars, in particular the dynamical evolution of the system in the merger phase, the associated anomalous nucleosynthesis and the dynamical ejection of part of the envelope, presumably producing the triple-ring nebula around the supernova.

The progenitor of SN 1993J on the other hand seems to have been a star mainly consisting of helium and heavier elements with a very small hydrogen-rich envelope. This again suggests that it was a member of a binary and that it lost most of its hydrogen-rich envelope by mass transfer. In both cases, future observations and theoretical calculations will be required to confirm or refute the suggested binary connections.

Type Ia supernovae have recently been used as cosmological distance candles (See Section 1.1.9) to measure the curvature of the Universe. At face value, the results suggest an accelerating Universe, a dramatic break from the previous picture. However, these results do not take into account possible evolutionary changes in the population of Type Ia supernova progenitors. Considering that there is no agreement on what the progenitor systems of these supernovae actually are, this seriously weakens the cosmological argument. We are presently studying various types of binary systems proposed as progenitors for Type Ia supernovae and model the evolution of the population of these progenitors since the early Universe, using binary population synthesis methods.

Hypernovae are a rare, new supernova type, first identified in 1998, which are much more energetic than a normal supernova and are probably caused by the collapse of a rapidly rotating helium star to a stellar-mass black hole. Some hypernovae are observationally known to be related to gamma-ray bursts, the most violent and most energetic events known in the Universe. Again our main interest is in understanding what type of stellar system can produce the progenitors of these spectacular events.

3.1.2 The formation and evolution of X-ray binaries and millisecond pulsars

Recent observations of the space velocities of pulsars (rapidly rotating neutron stars) have shown that when neutron stars are born in a supernova they receive very large kicks (presumably due to an asymmetry in the supernova explosion). This has important effects on the orbital parameters and the Galactic distribution of neutron stars in binaries. We are particularly interested in so-called low-mass X-ray binaries (LMXB), where a low-mass star with the mass of the Sun or less transfers matter to a neutron star, which as a result becomes a luminous X-ray source. While supernova kicks are important for understanding the formation of LMXBs in the Galactic disc, in dense stellar environments like globular clusters, other processes may be more important. For example, in globular clusters, LMXBs may form as a result of the tidal capture of a neutron star by a normal star. However, whether this is a viable process depends on the response of the normal star when the tidal energy is deposited inside the star (the tidal energy can be a large fraction of the binding energy of the star). During the LMXB phase, it is generally believed that the neutron star is spun up by accretion of matter, leaving a millisecond pulsar once the X-ray phase has ended. However, statistical comparisons between millisecond pulsars and LMXBs suggest that there are either too many millisecond pulsars relative to the number of LMXBs or that the duration of the LMXB phase has been overestimated by a large factor. This latter, more likely, possibility may be understood by irradiation effects which can dramatically change the structure of the irradiated normal star. In particular, the secondary may become inflated which leads to accelerated evolution and a shorter duration of the LMXB phase. The details of this process depend, however, on the circulation inside the secondary caused by the one-sidedness of the irradiation in a binary. This is an important problem which we are actively studying at the moment, developing both the theoretical framework and the numerical tools to tackle this problem.

One of the most important recent discoveries in this field, which indeed may challenge the above paradigm for LMXBs, is the realization that many stars in so-called Òlow-massÓ X-ray binaries originate from much more massive progenitors (e.g., Cyg X-2, Cyg X-3). Based on our recent calculations, it now seems that a large fraction, if not the majority, of low-mass X-ray binaries may actually belong to a much more massive, previously largely ignored class of intermediate- mass X-ray binaries, and that standard textbooks on the subject need to be rewritten. Apart from modelling individual systems, we use binary populations synthesis techniques to model the population of X-ray binaries (with US collaborators) and keep active collaborations with observational groups to test our predictions and improve our modelling efforts.

The formation of planets around pulsars (indeed, the first planets outside the solar system were discovered around pulsars) is a related problem of much current interest. Many massive X-ray binaries are predicted to merge in the near future. As a result of a complete merger, the neutron star sinks to the centre of the massive star forming a new hybrid object, generally referred to as a Thorne-Zytkow object (TZO). While no such TZO has yet been discovered, recent theoretical calculations predict that these objects should show anomalous surface abundances of many chemical elements which should be easily detectable spectroscopically. We are planning to use these predicted anomalies to search for these objects observationally.

3.2 Observations and modelling of stellar atmospheres

A knowledge of stellar abundances is crucial to our understanding of stellar and galactic evolution. While most stars have solar abundances or are metal-deficient with respect to the Sun, more pronounced abundance anomalies are also found. A few stars, for instance, have photospheres composed of 99% helium and 1% carbon (by numbers) with all other elements (including hydrogen) present only in trace amounts. Detailed abundance studies of stars in external galaxies (beyond the Magellanic Clouds) are becoming feasible using the HST and 10 metre class ground-based facilities. Improved techniques for the analysis of stellar spectra are under development; these take advantage of better computer hardware, numerical methods and (most important of all) recent advances in atomic and molecular physics. Synthesis of whole spectral regions with inclusion of all likely spectral features is now a viable method of approach.

Subdwarf-B (sdB) star research is of interest to investigations of stellar mass-loss, as these stars appear to represent extreme cases of near complete envelope loss during the later stages of stellar evolution. If most stars evolve through the sdB star stage, following evolution up the giant branch, understanding the envelope loss which results in sdB star formation is crucial to understanding the late stages of stellar evolution; it would also be the key to understanding chemical evolution of a galaxy or star cluster over several stellar generations. A recently published better understanding of sdB star evolution should help determine the contribution of sdB stars to the observed ultraviolet upturn in giant elliptical galaxies, with the view to its calibration as an age indicator. Following the exciting discovery of low-amplitude pulsation in seventeen sdB stars, the techniques of asteroseismology are being used to constrain stellar evolution models through a determination of envelope structure. The intention is to establish sdB star envelope structure by determining the dispersion relation of acoustic or gravity waves in surface layers, where wave scattering can be accurately computed.

4. The interstellar medium

P Roche

The interstellar medium is the repository for recycling material between tenuous, diffuse regions and dense molecular clouds where a large fraction can be cpnverted into stars where it is locked up for long periods before being ejected back into the ISM through stellar winds or other outflows. Patrick Roche is probing star forming regions to investigate the formation of low mass stars and planetary mass objects with the aim of increasing our understanding of these common, but poorly-understood members of the Galactic stellar population and the mechanisms by which they form. In turn this will give new information on the fragmentation of molecular clouds as they collapse to form stars. Fiona Riddick is completing her D.Phil thesis on the low mass H-R diagramme in the Orion nebula, which will provide estimates of the timescale for star formation and test theoretical models of very young (~1Myr) recently formed stars and brown dwarfs. Very different conditions hold in the nuclei of starburst and active galaxies, but here too interstellar material plays a key role, often girdling the galaxy nuclei and hiding them from direct view and leading to different classifications of Seyfert galaxies. New instruments on the Gemini 8-m telescopes allow us to investigate these dusty circumnuclear regions at high spatial resolution for the first time. Early results indicate that it is possible to trace cool material out to 10s of parcsec from the nucleus, and we are now extending these measurements to a larger sample of nearby galaxies.

5. Astronomical instrumentation

5.1 Infrared and visible wavelength instrumentation

G Dalton, R Davies, I Hook, I Lewis, P Roche, M Tecza, N Thatte.

The astronomical instrumentation group at Oxford has expanded rapidly in the last year, with a strong influx of new personnel and new projects. We are now involved in designing, fabricating and deploying second generation instruments at three different 8-meter class telescopes - the European Southern Observatory's Very Large Telescope (VLT), the Gemini telescopes and the Japanese Subaru telescope. In addition, Oxford hosts the UK's Gemini Support Group which seeks to assist UK observers with preparation and exploitation of their Gemini programmes, putting us in an ideal position to exploit these facilities. We are also involved in a joint OPTICON-PPARC effort to define and develop science programs for the next generation of 30 and 100 meter telescopes (ELTs). The Oxford instrumentation group have recently won a Marie Curie Excellence Grant from the European Commission for the design and realisation of SWIFT, a novel integral field spectrograph. SWIFT will provide integral field capability covering the wavelength range 0.7 to 1.0 micron. SWIFT's novelty stems from the combination of a very high throughput image slicer based integral field unit, a CCD detector with very high sensitivity at red wavelengths, and the enhanced sensitivity and resolution afforded by an adaptive optics system. It is a fast track project, to be realised over a four year timescale. A dedicated team of five researchers has already begun working on the project. SWIFT will explore the kinematics and dynamics of galaxies at moderate and high redshift, using emission lines shifted into its bandpass. Additional financial support is also available from the University.

We are the principal UK partners with Japan in the construction of a wide-field, multi-object, infrared spectrograph project (FMOS). This will be fed by a robotic fibre-optic positioning system at the prime focus of Japan's 8.3m Subaru telescope. FMOS will see first-light in early 2005, and provides an excellent opportunity for a D.Phil student to become involved in the laboratory testing and science verification phase of the instrument which will address a wide range of science programmes from brown-dwarf stars to the evolution of galaxies at high redshifts.

Together with consortium partners in Germany (MPE, Garching and USM, Munich) and the UK (Univ. of Durham, UKATC) we have won a competitive bid to design and construct KMOS, the cryogenic, multi-object, near-infrared spectrometer for the ESO VLT. KMOS will be one of the VLT's second generation instruments, and will represent UK's major contribution to VLT instrumentation. KMOS will be equipped with deployable mini integral field units, thus providing spatially resolved information of over two dozen targets within a 7 arcminute diameter field. Oxford will be responsible for the spectrograph module of KMOS, and for part of the data analysis and reduction software. KMOS is expected to be operational in 2009.

We are also involved in a large consortium that will carry out a feasibility study for WFMOS, the most challenging of the Gemini second generation instruments. WFMOS will provide simultaneous spectra of ~5000 galaxies spread over a 1.5 degree field of view, in order to answer fundamental questions about the complexity of the Universe and to determine the equation of state of dark energy. It is a very ambitious project, as it will require major modifications to the Gemini telescope, and to the way in which the Observatory is run. At present, a feasibility study is being carried out.

Through a developing link with the CLRC's Rutherford Appleton Laboratory (also involved in the FMOS project) we are also contributing to the design and construction of a new 4-m. class survey telescope (VISTA) which will be sited close to the VLT in Chile in 2006. VISTA hosts a uniqe wide field Infra Red camera which will be used to construct a deep survey of the entireSouthern sky to provide targets for the VLT, Gemini and the Next-Generation Space Telescope.

Finally, Oxford scientists are working with colleagues in Europe to define the next generation of Extremely Large Telescopes (ELTs). These ground-based telescopes are expected to have diameters in the range 30-100m, and will operate at optical and infrared wavelengths. We are involved in the definition of the science case for such a telescope, with particular focus on the larger end of the range, from 50-100m (this work is supported by the European network OPTICON) Oxford is also involved in a major European technical design study for an ELT. Our main areas of involvement in the study are in setting the scientific requirements for an ELT and studying potential ELT instruments.

Further information

5.2 Experimental radio and mm-wavelength cosmology

Mike Jones, Ghassan Yassin, Angela Taylor, Paul Grimes

The experimental cosmology group designs, builds and then uses new instruments for studying the evolution and structure of the Universe. The group is involved in a wide-range of projects covering a whole range of frequencies, from low radio frequecies to hundreds of GHz, and develops novel techniques to be used in future experiments.

Further information on the Experimental Cosmology group

5.3 The UK Gemini Support Group

R. Johnson, D. Rigopoulou, P. Roche, I. Soechting

The UK is a 25 percent partner in the international Gemini Observatory which operates two 8-m telescopes on the best observing sites in the world, Mauna Kea in Hawaii and Cerro Pachon in Chile. The UK Gemini Supportgroup is based in Oxford and provides user support for all UK users of Gemini as well as some specialist support for the international Gemini community. The group also coordinates the UK scientific perspectives on the telescopes, instruments and operations and represents these to our international partners.

Further information