D.Phil. projects 2012

Molecular gas and star formation in early-type galaxies

Advisor: Martin Bureau

Early-type galaxies (ellipticals and lenticulars) are generally
considered "red and dead", as they have homogeneously old stellar
populations. They also harbour most of the stellar mass and, as its
end point, are crucial to understand galaxy evolution. However, a
large survey we recently completed as part of the Atlas3D project has
surprisingly revealed that many early-types possess a substantial
amount of molecular gas, the fuel for star formation. This successful
survey revolutionised our view of the interstellar medium of
early-type galaxies, revealing in particular that 50% of it comes from
external accretion overall (presumably gas-rich minor mergers), while
this accretion is shut down in cluster of galaxies.

But how can early-type galaxies harbour all this molecular gas and not
form stars? Preliminary studies reveal that they may be forming stars
rather inefficiently, i.e. they do not follow the standard
star-formation scaling relations obeyed by spiral galaxies. The key
must lie in the dynamics and physical conditions of the gas. To probe
this, we need to observe tracers of the molecular gas density,
opacity, temperature, etc, such as various transitions of the
molecules HCN, HCO+, 13CO, etc, visible at mm and sub-mm
wavelengths. This is possible by using observations with the best
existing mm/sub-mm interferometers, such as CARMA and PdBI, exploiting
the early science phase of ALMA, the largest ground-based telescope
project in existence, and modeling the line ratios with dedicated
software. All these ingredients are in place in Oxford.

Building on our current work, the student will thus plan, reduce, and
analyse mm/sub-mm interferometric observations of molecular gas in
nearby galaxies, and infer the physical conditions in the gas through
modelling, this in the hope of explaining why star formation in
early-type galaxies differs so markedly from that in spirals.

The Tully-Fisher relation at intermediate redshifts with KMOS

Advisor: Martin Bureau, collaborator: Roger Davies

The Tully-Fisher (luminosity-rotational velocity) relation offers a
powerful tool to probe the evolution of galaxies, as its zero-point
provides a direct estimate of the mass-to-light ratio (M/L) of the
objects studied. However, the traditional neutral hydrogen (HI) probe
in spirals can not yet be observed beyond the local universe, and the
ionised gas emission lines often used locally are redshifted in the
near-infrared part of the spectrum at intermediate redshifts, making
observations technically difficult and time-consuming. Since using a
single tracer and measurement method is crucial to avoid systematic
biases on any zero-point offset measured, it has proven difficult
(arguably impossible yet) to use the Tully-Fisher relation to reliably
probe the M/L evolution of disk galaxies across lookback times
(redshifts).

Fortunately, Oxford is part of the consortium that built KMOS, a
second generation Very Large Telescope (VLT) near-infrared
spectrograph with multiple deployable integral-field units
(IFUs). KMOS allows to obtain data like velocity fields for 24
galaxies simultaneously, and thus to obtain very deep exposures. With
its large VLT guaranteed time allocation, Oxford has already decided
to pursue a Tully-Fisher study of disk galaxies at redshifts ranging
from 1 to 2.5, thus probing the crucial epoch where gas-rich turbulent
disks evolve into the regular spiral galaxies we see today. Standard
deep fields covering the whole range of masses and environments will
be used (CANDELS), and the modelling tools required to extract the
velocity measure have already been developed in the context of
high-redshift spectroscopic studies.

The student will participate in the target selection for the KMOS
survey, followed by planning and analysing the VLT observations, as
well as dynamical modelling of the data. Proper comparisons with local
samples will also need to be developed. This project ideally
complements the ALMA CO Tully-Fisher work proposed separately, and
much synergy is expected.

The CO Tully-Fisher relation at intermediate redshifts

Advisor: Martin Bureau, collaborator: Roger Davies

The Tully-Fisher (luminosity-rotational velocity) relation offers a
powerful tool to probe the evolution of galaxies, as its zero-point
provides a direct estimate of the mass-to-light ratio (M/L) of the
objects studied. However, the traditional neutral hydrogen (HI) probe
in spirals can not yet be observed beyond the local universe (less
extended and more disturbed ionised gas is used instead), and
early-type galaxies usually lack any circular velocity tracer (arduous
and time-consuming stellar dynamical modelling is occasionally
used). Since using a single tracer and measurement method is crucial
to avoid systematic biases on any zero-point offset measured, it has
proven difficult (arguably impossible yet) to use the Tully-Fisher
relation to probe M/L evolution across both lookback time (redshift)
and/or morphological type (mass).

Unexpectedly, we have recently shown that molecular gas is present in
substantial amounts in early-type galaxies, and that it is an
excellent tracer of their circular velocity. Molecular gas (e.g. CO)
thus offers an ideal kinematic tracer for all galaxy types from dwarfs
to ellipticals, and with the advent of ALMA and the LMT it will be
routinely observable for the bulk galaxy population up to redshifts of
at least 2. We have already provided a z=0 reference for early-type
galaxies, and are currently engaged in a large NANTEN2 programme for
local spirals and dwarfs (the only telescope able to capture entire
nearby disk galaxies at once!). The modelling tools required to extract
the velocity measure have already been developed in the context of
high-redshfit spectroscopic studies. We thus propose here to carry out
a CO-based Tully-Fisher study up to intermediate redshifts (z~2), in
the standard deep fields in the South (CANDELS), covering the whole
range of masses and environments.

The student will plan and analyse the observations (ALMA+LMT), as well
as carry out the dynamical modelling work (ALMA only). This project
ideally complements the KMOS spiral-only Tully-Fisher work proposed
separately, and much synergy is expected.

Measuring black holes masses with ALMA

Advisor: Martin Bureau, collaborator: Michele Cappellari

Understanding the formation and evolution of galaxies is central to
much of contemporary astrophysics. The black hole mass - stellar
velocity dispersion (M_BH-sigma_stars) relation and its derivatives
imply a tight link between the growth of central supermassive black
holes (SMBHs) and that of galaxies, and these relations now underlie a
staggering number of observational and simulation works. However, the
number of reliable measurements on which the relations rely is small,
and the number of independent measuring methods even smaller. Having
recently shown that the molecular gas in galaxies is an accurate and
arguably the best tracer of the circular velocity of galaxies across a
wide range of radii, we propose here to exploit this fact to measure
SMBHs masses in a large sample of local galaxies spanning a range of
morphological types and masses.

With the revolutionary sensitivity and angular resolution of ALMA, the
largest ground-based telescope project in existence, we will probe the
physical conditions and kinematics of the molecular gas in galaxies to
the smallest spatial scales yet, well within the sphere of influence
of the SMBHs (largely Keplerian rotation). We have already developed
the tools to model the derived velocity fields (and cubes), including
the influence of the galaxy stellar potential, the SMBH itself, and
possible non-circular motions. We are also testing our method on one
of the few objects accessible with current telescopes. The
measurements are straightforward and robust, will significantly
increase the number of reliable SMBH masses available, and will
totally renew our understanding of the M_BH-sigma_stars relation.

The student will plan and analyse the mm interferometric observations
and carry out the dynamical modelling work, first through pilot
observations in the development phase of ALMA, and then during routine
operations.

Testing General Relativity with Weak Lensing

Prof Pedro Ferreira and Prof Lance Miller

With the tremendous advances in astronomy it is now possibly measure how light
is distorted by weak distortions of space time- a phenomenon known as Weak Lensing.
The patterns in these distortions may be used to learn something about gravity and
General Relativity. In particular it may be used to test alternatives of General Relativity.
In this projects we wish to forecast how well current and futures surveys will
constrain General Relativity, search for novel statistical methods which applied to
weak lensing surveys might be specially sensitive to modified gravity and extract
constraints from some of the surveys in which we are involved at Oxford.

The impact of relativistic fields on the growth of non-linear structure

J. Devriendt and P. Ferreira

Current numerical methods for studying the non-linear growth of structure are
firmly entrenched in the Newtonian non relativistic limit. Yet some of the current
proposed sources of dark energy, dark matter and modified gravity are inherently
relativistic. We wish to build an N-body simulation that correctly incorporates
relativistic fields and allows us to study a wide range of statistics, from the formation
of clusters, cluster counts and their overall impact on large scale structure. As a first
step we would work with a PM code but, if time allows, we would work up to
one of the AMR codes that that the group currently works on.

Supernovae and Cosmology

Dr Mark Sullivan and Prof Isobel Hook

Oxford is involved in the Palomar Transient Factory and with major new
survey projects that are due to start in 2012. Many projects
are available using these large datasets, and students would be
directly involved in carrying out follow-up observations at the
telescopes and scientific analyses of the data. Two example projects
are described below.

1. PTF (Palomar Transient Factory) is a highly-successful survey of
the local Universe designed to systematically hunt for nearby Type Ia
Supernovae for future dark energy analyses. The survey has been
running since 2009 and we are carrying out a large observational
follow-up campaign to obtain spectra and multi-epoch light curve
photometry for PTF discoveries. A large amount of data is now hand
including a uniquely large sample of i-band lightcurves. One project
involves analysing the lightcurves and adapting current light-curve
fitting tools to work in the i-band. The student will then use these
tools to analyse new data from the VISTA 4m telescope in Chile that
will measure near-infrared lightcurves of supernovae at intermediate
redshifts (hence sampling the rest-frame i-band). The data and
analysis tools will form an important reference set for future
infra-red supernova surveys for cosmology such as that from ESA's
Euclid mission.

2. PESSTO (Public ESO Spectroscopic Survey for Transient Objects) is a
major new spectroscopic survey, starting in April 2012, that will
generate vast quantities of spectra of nearby supernovae and other
transient objects. Together with corresponding photometric
measurements, these data can be used for studies of Type Ia supernovae
for cosmology, and also for exploring extreme events: ususual
supernovae that provide insight into the physics of their explosion
mechanisms and environments. There will be opportunities for the
student to take part in PESSTO observing runs in Chile.

Reshaping galaxies with outflows

Julien Devriendt, Andrew Pontzen and Adrianne Slyz

The past few years have seen a seismic shift in the way we think about the role of baryons in galaxies. While it has long been understood that gas flows into dark matter halos and cools to form stars, observations and state-of-the-art numerical simulations now provide compelling evidence that a large fraction of gas is subsequently re-ejected in "outflows".

We are starting to realize that these outflows radically change the nature of the galaxies that they leave behind. However there is little agreement on the exact fraction of gas involved, the speed and size of the outflows, or even the physics leading to the gas expulsion. The observational evidence requires comparison with numerical and physical models before this situation can be clarified.

This project is suitable for a strong D.Phil. student and will involve running and analysing cutting-edge numerical simulations (AMR and, through an international collaboration, SPH). There is scope for analytic modelling and for direct comparison to observational datasets. The result will be a timely thesis and a broad skill-set covering computational, theoretical and observational methods.

Gravitational lensing with ACTPol

Jo Dunkley

The polarized Cosmic Microwave Background is gravitationally lensed by cosmic structures that lie in its path. This gives a direct probe of the integrated dark matter over cosmic history, and provides a way of measuring the growth of structure in the universe, shedding light on properties of dark energy and dark matter. In Oxford we are collaborating on ACTPol, an experiment to measure the polarized CMB from the Atacama Desert in Chile, due to run from 2012-15. This PhD project will involve extracting cosmological information from the ACTPol lensing signal, including testing dark energy models or modifications to gravity, and constraining the mass of the neutrino. Cross-correlation of CMB lensing with other probes of cosmic structure will also be explored, including high redshift (z~1-4) dusty galaxies, and weakly lensed galaxies. The project will combine theory with data analysis, and would involve collaboration with the ACTPol team.
For more information contact Jo Dunkley (j [dot] dunkley [at] physics [dot] ox [dot] ac [dot] uk).

Gravitational waves from inflation

Jo Dunkley
A major goal in cosmology is to determine whether inflation happened, a rapid expansion of the universe at early times. A detection of gravitational waves, ripples in space-time imprinted during inflation, would provide strong evidence in favour of this scenario. These waves show up as B-mode patterns in the polarization of the Cosmic Microwave Background, but the expected signal is very small. To extract the primordial B-mode signal requires removing a polarized signal from the Milky Way, and from gravitational lensing of the CMB itself. This project will focus on using data from the Planck satellite to understand and model these two contaminants, to analyze current data, and to inform the design of upcoming B-mode experiments.
For more information contact Jo Dunkley (j [dot] dunkley [at] physics [dot] ox [dot] ac [dot] uk).

The Extensive Galaxy Zoo LENsing Survey

Dr Aprajita Verma, Dr Matthias Tecza, Dr Phil Marshall
The phenomenon of gravitational lensing, predicted by general relativity, is one of the most spectacular astronomical processes that we observe. A single galaxy, a group or cluster of galaxies can act as "cosmic telescopes" amplifying and magnifying the light of galaxies lying behind them into multiple images, rings or arcs. This process is entirely determined by the distribution of dark and light matter in the lensing galaxies themselves. Understanding the distribution of this matter, as well as the nature of the background lensed galaxies are the goals of this DPhil project. The student will work on a sample of new strong lenses discovered by members of the public as part of the Galaxy Zoo project. We have short-listed a sample of nearly 30 high priority potential lenses that we are observing at prime facilities to confirm their lensing nature. The first part of the project will be to model the light and dark matter distribution of the lens candidates making significant developments on an existing simulation tool for Galaxy Zoo users. Concurrently the student will work on the data we already have in hand to extract redshifts and dynamical information on the lensing galaxy. This kinematic information will be folded into the simulation tool to improve the model and providing strong constraints on the profile of the dark matter halo of individual galaxies and galaxy groups. We will also investigate the nature of the lensed galaxies as the magnification and amplification allows fainter galaxies than would be normally possible to be observed and allows intrinsically smaller scales to be studied. The student will also contribute to extending the EGZLenS project to new samples being ingested into Galaxy Zoo as well as assisting with observing runs and preparation, writing proposals and liaising with lensing enthusiasts in Galaxy Zoo.
Please contact averma [at] astro [dot] ox [dot] ac [dot] uk for further information.

Galaxy Zoo at high Red Shift

Prof Joe Silk, Dr Chris Lintott, Dr Arfon Smith, Dr Garret Cotter
Understanding how the observed population of galaxies came to be is critical to testing modern models of the evolution of the Universe, and critically depends on the availability of large catalogues of classified objects. The Oxford-led Galaxy Zoo project (www.galaxyzoo.org) has been successful in recruiting a large number of members of the public to provide morphological classifications of nearly 1 million local galaxies. Analysis of this data has already given us several new insights into the present-day galaxy population, including the identification of blue ellipticals and red spirals. These objects, which reverse the expected relationship between colour and morphology provide the keys to understand how the rest of the galaxy population we see today evolved. The next incarnation of Galaxy Zoo will provide classifications of galaxies drawn from Hubble Space Telescope surveys (including GOODS and COSMOS); this project will involving being among the first to analyse the resulting data with the aim of understanding the morphological differences between the galaxy populations at a redshift of ~1 and today. There will also be opportunities for observational follow-up. As the project depends on the contribution of volunteers, it would particularly suit a candidate with an interest in outreach as well as research. Contact cjl [at] astro [dot] ox [dot] ac [dot] uk for more information.

Lifecycles and dutycycles of active galaxies

Prof Katherine Blundell
The last few years has seen a complete reversal of the disinterest of those working in galaxy formation modelling towards AGN, into urgent interest in how they feedback heat and matter into IGM and influence their surroundings. This project aims to delineate the changing roles played by the two means of energy loss from AGN: (intermittently) from jets and (persistently) from accretion disc winds (Blundell & Kuncic, ApJLett, 2007) by using very low-frequency radio observations together with sub-mm monitoring observations.

Do distant high redshift submillimetre-luminous galaxies harbor a black hole?

Dr Dimitra Rigopoulou
The discovery of apparently old elliptical galaxies at z>2 has pushed the question of starburst progenitors of giant ellipticals to even earlier epochs. Such galaxies must have formed the bulk of their stellar populations at z>4. Wide field blank sky surveys at submillimetre wavelengths have discovered a number of high redshift star forming galaxies (SMGs) with the majority being at z~2.

The COSMOS survey, however, has unveiled a number of high redshift SMGs (z~5) which could potentially be the progenitors of the recently discovered z~2 giant ellipticals. The project will focus on these high redshift SMGs from COSMOS and combining unique data from ESA's Herschel Space Observatory will investigate the existence (or not) of a black hole in their centres. The project will involve analysis of SPIRE/PACS data, modelling of SEDs with the aim of unveiling the true nature of these sources.

We are looking for an enthusiastic D.Phil student who will get involved with reduction and analysis of data from the Herschel Space Observatory. Modelling and and followup observations of these highly interesting objects will enable us to unravel the energy mechanismsbehind the prodigious amounts of energy emitted by these objects

Please contact d [dot] rigopoulou1 [at] physics [dot] ox [dot] ac [dot] uk if you would like further information.

Studying "Bumpies" (obscured Star Formation at high redshifts) with KMOS.

Dr Dimitra Rigopoulou, Professor Niranjan Thatte, Dr Matthias Tecza and Prof Roger Davies
Ultra-luminous infrared galaxies (ULIRGs) are dust-enshrouded systems harbouring intense star formation activity. These objects have complex morphologies, and often show signs of recent interactions/mergers. The latest generation of infrared satellites (Spitzer, Herschel) have provided robust samples of ULIRGs at z~2 and beyond, where these objects are 100 times more numerous than their well studied counterparts in the local Universe. KMOS, the VLT multi-object near-infrared spectrograph, expected to be commissioned in late 2011, will allow us to study the complex morphologies and kinematics of a particular subset of these objects - "bumpies", or objects identified by their characteristic H-band stellar bump red-shifted to the Spitzer IRAC bands. We are able to fully characterise the SEDs of these objects, thanks to multi-band Herschel photometry also being available. Oxford is intimately involved with the construction of KMOS, and expects to participate substantially in the GTO program, of which these observations may form a part.

We are looking for a motivated D.Phil student who would engage with the observations, reduction and analysis of data from this 2nd generation instrument, whose high multiplex factor makes statistical spectroscopic studies (at near-infrared wavelengths) of the distant Universe possible for the first time!

Please contact d [dot] rigopoulou1 [at] physics [dot] ox [dot] ac [dot] uk if you would like further information.

The C-Band All-Sky Survey – C-BASS

Dr Angela Taylor and Professor Mike Jones
Observations of the cosmic microwave background radiation (CMB) have transformed our understanding of the universe over the past twenty years. The next big milestones will be the release of the data from the Planck satellite in 2012, and the possibility of detecting the curl-like component of the polarization of the CMB (the 'B-mode'), which will directly probe the physics of Inflation. One of the biggest problems as the sensitivity of CMB experiments gets ever better is removing the effects of foreground radiation, particularly from our Galaxy. Oxford Astrophysics, in collaboration with Manchester, CalTech and SKA South Africa, is building a pair of all-sky survey telescopes to definitively measure the synchrotron emission from the Galaxy in intensity and polarization, to improve foreground subtraction and hence significantly improve the sensitivity of experiments such as Planck. C-BASS will also provide new insights in to the Galactic magnetic field and the properties and emission mechanisms of the interstellar medium. C-BASS North, at Owens Valley Radio Observatory in California, is already observing, and C-BASS South, at the MeerKAT site in Western Cape, South Africa, will be completed during 2011. The student on this project will join the small team reducing and analysing C-BASS data, ensuring that the survey data is as accurate and reliable as possible, before then using it in conjunction with Planck data to provide accurate measurements of the CMB temperature and polarization spectra.

Understanding the physics of galaxy clusters using the Sunyaev-Zel'dovich effect

Dr Angela Taylor and Professor Michael Jones

The Sunyaev-Zel'dovich effect is a unique way of looking at clusters of galaxies, the largest building-blocks of the universe. Instead of detection radiation emitted by the clusters, we see the cluster gas in silhouette against the cosmic microwave background, as the hot gas in the cluster scatters the radiation passing through it. The SZ effect has the unique property that its surface brightness is independent of redshift, making it an important tool for both cosmology and astrophysics.

Several experiments around the world are currently making surveys of clusters using the SZ effect. The distinct spectral distortion carries important information about the cluster physics, but to fully exploit this we need to make sensitive measurements over a very wide range of frequencies, from around 30 GHz to over 250 GHz.

We are currently planning, with colleagues in the UK, SA and USA, new experiments which will make detailed images of the SZ effect over this full range of frequencies. In addition we also have data in hand from our current SZ experiment, the Cosmic Background Imager, and are expecting to have data soon from our new prototype 220 GHz SZ interferometer, GUBBINS.

This project will involve simulation of upcoming experiments, the analysis and interpretation of current data and the development of existing and new theoretical models of galaxy clusters.

For more information please contact: Angela Taylor (act [at] astro [dot] ox [dot] ac [dot] uk) or Mike Jones (mike [at] astro [dot] ox [dot] ac [dot] uk)

High-frequency radio line and continuum surveys: Star formation and active galaxies in the very early universe.

Dr Ian Heywood, Dr Angela Taylor, Prof Mike Jones, Dr Garret Cotter

Around 300,000 years after the Big Bang, the temperature of the Universe had dropped sufficiently that neutral Hydrogen atoms first formed, signalling the start of the so-called "dark ages" that only came to an end once radiation from the first stars, galaxies and black holes re-ionized the Universe. This project is concerned with making some of the first direct observational studies between the highest redshifts that are presently well-studied and this so-called Epoch of Reionization (EoR) at z ~ 7 to 10.

We hope to recruit one or two students to take the lead in obtaining and analysing radio and sub-millimetre interferometry data to complement optical and infra-red survey work with collaborators at Herts, Liverpool and Edinburgh, and to carry out theoretic simulations of the embryonic environment of stars, gas and black holes at these very high redshifts.

Specific opportunities are:

1. Making first detections of CO in the EoR. The student will be involved in deep radio imaging with the new Karl G. Jansky Very Large Array aimed at making the first detections of CO in the EoR, and planning for the Key Project MESMER already awarded 6500 hours on the MeerKAT array under construction in South Africa. This will be coupled to ALMA and VLA programmes studying CO-ladder line ratios at lower redshifts.

2. Testing and refining the simulations of CO at high redshift using the new measurements. The existing semi-analytic simulations developed for the SKA Design Study (SKADS) are predictive into the EoR, but real measurements are likely to unearth needed refinements to the assumed physical prescriptions. The student will use these refined simulations to optimize the MESMER observing strategy, and use the VLA to attempt the first measurement of large-scale structure in the EoR using CO, and CO/Lyman-alpha cross-correlation.

3. Simulating and potentially making the first cross-correlation analyses of large-scale structure in the EoR as traced by CO (VLA/MeerKAT/ALMA), HI (e.g. LOFAR ) and Lyman-alpha-emitting galaxies (e.g. VISTA). Mapping of the power-spectrum of the Universe in the EoR is one of the key goals of phase-1 of the Square Kilometre Array (SKA). The PhD student may be involved in foreshadowing this science by making statistical detections of EoR features using cross-correlation techniques. Their results and simulations should certainly influence the final design of the SKA.

4: Using the continuum data that comes for free alongside the molecular line observations to study the most distant active galaxies at high radio frequency. Extragalactic radio sources are some of the most energetic phenomena in the universe, but our knowledge of them is biased by the fact that all large complete surveys of them to date have been made at relatively low radio frequencies, where the radio brightness is dominated by the emission from the large lobes of material ejected from the central black hole rather than the central engine itself. Technical advances in instrumentation mean that high-frequency surveys can now be done, selecting objects on the basis of the core emission region to characterise and understand this source population.

Discovering Galaxies in the Early Universe with the Hubble Space Telescope

Dr Andy Bunker and Dr Stephen Wilkins
There is a project available to work with Andy Bunker and Stephen Wilkins on measuring the star formation rate in very distant galaxies (at redshifts well beyond one), using Hubble Space Telescope data and follow-up spectroscopy from large ground-based telescopes in Chile and Hawaii. The science goal is to map the average rate at which the Universe forms stars as a function of time, and to assess whether the ultra-violet photons from the most massive stars could have produced the reionization of the Universe, which we know occurred at high redshift.

The Evolution of Star Formation and Metallicity in the Universe

Dr Andy Bunker and Prof Gavin Dalton
There are PhD projects available to work with Andy Bunker's team using the new FMOS spectrograph on Subaru (in collaboration with Gavin Dalton) and the forthcoming KMOS spectrograph on VLT.

FMOS is a multi-object spectrograph working in the near-infrared, and has been jointly built by Oxford and Japan for the Japanese Subaru telescope in Hawaii. The spectrograph is in operation now, and we intend to measure star formation rates and metallicities for many galaxies around a redshift of one - an important epoch when the star formation activity in the Universe may have peaked. Most of the crucial emission lines used in this study fall beyond visible wavelengths at this redshift, and only FMOS offers the field of view capability to observe large number of galaxies (400 at once).

The FMOS data will be complemented by a Hubble Space Telescope near-infrared slitless spectroscopy programme, WISPS, on which Andy Bunker is a co-investigator.

A complementary approach involves studying the kinematics of galaxies at high redshift by mapping the velocity shifts of these emission lines across these galaxies by using an integral field spectrograph to take a "3D" spectrum.

KMOS will be able to do this for more than 20 galaxies at once, and it is being built for the European Very Large Telescope in Chile by a consortium including Oxford. We intend to use KMOS to "weigh" galaxies at high redshift and to determine how the masses correlate with the luminosities and star formation rates, and how all these key properties evolve with time.

Galaxy evolution from z=2 to the present

Professor Roger Davies, Dr Michele Cappellari, Dr Ryan Houghton and Professor Niranjan Thatte
These projects explore the evolution of galaxies from z=2 to the present day utilizing diagnostics in the visible and infrared spectral regions that are well established in local galaxies. Single and multiple object integral field spectrometers (SWIFT, FLAMES, KMOS) enable global properties of galaxies to be measured and the complex structure of high redshift objects to be probed.

The Initial Mass Function: how many low mass stars are there in galaxies?

This important question has been difficult to answer because low mass stars (< 0.3 solar masses) contribute only a very small fraction of the integrated light of galaxies. However there are two spectral features in the far red that are sensitive to the presence of these dwarf stars, Na 819nm & the FeH band at 991nm a wavelength regime where the Oxford SWIFT spectrograph is amongst the most sensitive in the world. In an high precision study with the Keck telescope van Dokkum & Conroy 2010, detect these features in galaxies in the Virgo and Coma clusters concluding that the early type galaxies in these clusters form far more low mass stars than are produced by the Milky Way, thus opening up the prospect that the interpretation of galaxy spectra in terms of the evolution of their stellar population needs to be radically re-visited. Is this result just reflecting the special physical conditions found in massive galaxy nuclei or is there a real range in the distribution of low mass stars masses formed in different types of galaxy? This project involves using the SWIFT spectrograph on the Palomar 5m telescope to measure these features as a function of radius in relatively nearby galaxies and has implications for the evolution of stars in galaxies at all redshifts. (a discussion relating to this project appears on http://www.bbc.co.uk/news/science-environment-11888362).

The evolution of galaxies in clusters

(a) The global physical parameters of galaxies, their masses, sizes, luminosity and composition obey scaling relations that give us clues to their evolution. One such relationship, the Fundamental Plane (FP), is closely related to the Virial theorem and can be used to determine how the stellar and dark matter components of galaxies evolve over cosmic time. There are several projects underway using this diagnostic. The Gemini/HST Galaxy Cluster project is exploring the evolution of X-ray luminous clusters from z=1 to the present using the FP and other diagnostics measured using Hubble images and spectra of 40- 80 galaxies per cluster from the Gemini GMOS spectrograph. By comparing the FP deduced evolution with that inferred from analysis of the stellar population we can deduce how the stellar and dark components of galaxies evolve.

(b) In a follow-on project we will also observe the clusters in CLASH, the HST multi-cycle treasury programme, aimed at determining the dark matter content of clusters and, separately, discovering high redshift supernovae. These clusters will have some of the highest quality HST imaging yet taken providing high quality morphological and structural information which our multiple-object spectroscopy will complement. This project will involve spectroscopic observation of galaxies in clusters and analysis of the structure, motions and composition of the stars to deduce how the galaxies have evolved. The CLASH project is described at: http://www.stsci.edu/~postman/CLASH/For_Astronomers.html

(c) A third component of this work involves using KMOS, the new multi-object infrared integral field spectrometer to be commissioned on the ESO VLT in 2011, to observe galaxies in clusters at z=1-2. We will start by observing the currently identified high redshift clusters and seek to identify using the signature they impose on the microwave background (the Sunyaev-Zeldovich effect). This project will involve deep imaging of the newly discovered clusters as well as multiple object spectroscopy. The work will focus on both the star formation history and dynamics of the cluster galaxies .

There is the potential to have more than one student working on galaxy evolution in rich clusters as a function of cosmic epoch.

Establishing stellar birthdays and dating

Prof Pat Roche
Star-formation is one of the key processes in astrophysics, but the details remain poorly understood. Knowledge of the numbers of stars of different mass formed in different environments is a vital parameter in understanding the star-formation history of our Galaxy and the stellar populations produced at different epochs. Recent observations indicate that while the mass function of intermediate mass stars has little variation, there may be very significant differences in low mass stars and brown dwarfs, Spectroscopy of M-type stars in young clusters indicates that high precision measurements of alkali metal lines in young stars and brown dwarfs may be a sensitive indicator of the surface gravity and hence age of these objects. Red and Infrared spectra of stars in clusters with ages estimated between 1 and 10Myr will be made at the NTT telescope in Chile to test whether it is possible to distinguish ages of 1 Myr both within individual clusters and between clusters of differing ages.

This project will establish a precise dating method for young stars and to investigate the star-formation history of the clusters.

How jet launch works

Prof Katherine Blundell
Exquisitely detailed, sustained, round- the-clock optical spectroscopy of the microquasar SS433's jets and disc will be starting in 2012 as the GLOBAL JET WATCH project gets underway. With a rich archive building up a unique dataset, it will be possible to examine the detailed behaviour of this object throughout orbital periods, precession periods, and flaring events, to understand the detailed interplay between the attraction of matter (accretion) and the expulsion of matter (via jets and winds). The goal of this project is to investigate and model the behaviour of the accretion disc as revealed by the optical spectroscopy before, during and after jet-flaring events.

Hydrodynamical Modelling of Common-Envelope Evolution and Stellar Mergers

Professor Philipp Podsiadlowski

Common-envelope evolution, where two two stars spiral towards each other inside a surrounding gaseous envelope, is one of the most important, but also one of the least understood phases of binary evolution. The objective of this project is to model this phase using different complementary approaches (combining 1-d stellar hydro calculations with realistic input physics and more approximate 3-d SPH simulations) and to assess the importance of various physical processes (e.g. recombination energy, accretion energy). The goal is to develop realistic physical criteria for the ejection of common envelopes and the merging of the stars with applications to gamma-ray bursts, planetary nebulae and supernova progenitors.

The Fireworks Initiative: Understanding Cosmic Explosions

Professor Philipp Podsiadlowski

This project is part of an international collaboration trying to understand the diversity of cosmic explosions, such as supernovae of various types, hypernovae and gamma-ray bursts, and their implications for the evolution of galaxies and the chemical evolution of the Universe. As part of this project, the student will explore theoretically how various progenitor channels can account for the observed diversity, examining the role of rotation, binary evolution and metallicity. This will involve performing stellar and binary evolution calculations and possibly simulations of whole stellar populations. One of the objectives is to develop observational predictions that can be tested within the framework of the fireworks project.

Testing exoplanet evolution by using gyrochronology

Dr Suzanne Aigrain

It is much easier to make a meaningful comparison of the properties of
exoplanets (masses, radii and orbital parameters) with the predictions
of theoretical evolutionary models if we know the planets' ages, but
that is a very difficult quantity to measure. In this project we will
apply a technique known as gyrochronology to estimate ages for the
host stars of planets discovered by the Kepler space mission, and
hence for the planetary systems themselves.

In two years of operation, Kepler has detected the transits of over
1500 candidate planets, some with radii less than twice that of the
Earth. Many more are expected over the coming years, including
potentially habitable planets. The Kepler light curves can also be
used to measure stellar rotation periods. The project will focus on
measuring periods for two groups of stars: a few hundred of the
brightest Kepler targets, for which relatively precise age estimates
will be available from asteroseismology, and the host stars of the
planet candidates. The first set will be used to improve the
calibration of the gyrochronology relations, which will then be
applied to the second to derive ages.

This is primarily a computer-based, data analysis project, using
advanced Bayesian statistical methods to model time-series data.
However, we are also carrying spectroscopic follow-up of some Kepler
stars to explore the impact of rotation on stellar evolution, so there
will also be an observational component.

For further information contact Suzanne [dot] Aigrain [at] astro [dot] ox [dot] ac [dot] uk.

Development of THz SIS mixer for ALMA band 11

Prof. Ghassan Yassin and Dr Dimitra Rigopoulou

In recent years, there has been extensive activity to develop ground-based and space telescopes to allow astronomical observations at millimetre and submillimetre wavelengths.
This is because the mm/submm part of the spectrum is rich in atomic, ionic and molecular lines that allow us to probe the ISM in our own and distant galaxies, as evidenced by the recent advent of the Herschel Space Observatory. In particular, a number of important ISM diagnostic lines such as the, relatively unexplored, [NII] 205micron fine structure emission line and a number of high-J CO transitions can be accessed. Thus, there are important scientific drivers for observing spectral lines at supra-THz frequencies, Such observations will provide a unique window that allows one to study the structure formation at the redshift regime of 0.5 The aim of the project is to explore and develop technical solutions that will support the construction of an heterodyne receiver operating in the highest atmospheric windows accessible from the best ground sites (1.36 THz and 1.5 THz) at an altitude of 17,000 feet at the Andes in Chile. Such a receiver will be suitable for use on APEX and ALMA (Band 11) and will enhance their capability to explore this exciting science.
The key component that needs to be developed for high resolution THz observation is the SIS (Superconductor-Insulator-Superconductor) mixer. In recent years, the performance of SIS based sub-millimetre wave receivers below 1 THz has achieved impressive sensitivity close to the quantum limit. Above 1 THz, however, RF loss in the superconducting circuits increases rapidly and the performance of the SIS mixer is limited by the efficiency of quantum assisted tunnelling above the gap frequency for the commonly used Niobium devices. The research works involved in this development is challenging both scientifically and technologically. It needs the extension of existing quantum mixing theories and electromagnetic models to cope with detection around the superconducting gap and accurate modelling of the mixer performance. It also requires the employment of state of the art technologies for testing these mixers such as cryogenic systems and accurate measurements of high sensitivity detectors. Work on this project will be carried out in collaboration with the Detector Physics group at Cambridge and the Space Science division at the Rutherford Appleton laboratory.
The project will suit an experimentally minded physicist who likes to combine theoretical and computational work with laboratory experimental tests.

WEAVE: Next Generation Multi-Object Spectroscopy

Prof Gavin Dalton and Dr Ian Lewis

Our group is leading the WEAVE project to build the next generation multi-fibre spectrograph on the 4.2m William Herschel Telescope on the island of La Palma, which will commence its final design phase in 2013. Within this programme there is an opportunity for a motivated student to work on aspects of the robotic fibre positioner design, integration and test, as well as to develop optimal strategies for efficient survey design using the instrument. There will be opportunities to work closely with WEAVE consortium partners in the Netherlands, Spain and France as well as other institutes within the UK. The WEAVE science programme covers a wide range of topics from the radial velocity and chemo-dynamical complement to the GAIA mission through to observational constraints on models for Dark Energy and gravity theories, and there will be opportunities for the student to develop a science theme on one of these areas during the instrument development. The WEAVE positioner development is also closely related to the EVE instrument proposed for the E-ELT, giving possible avenues for the studentship to develop in this direction at a suitable point.

Science with HARMONI, a first-light instrument for the European Extremely Large Telescope

Supervisor: N. Thatte. Collaborators: I. Hook, M. Tecza, A. Verma, F. Clarke

The European Extremely Large Telescope (E-ELT, http://www.eso.org/sci/facilities/eelt) will be the world’s largest visible/infrared telescope. With a primary mirror diameter of 39 m, it will have more collecting area than ALL the world’s telescopes built to date. The HARMONI instrument (http://astroweb1.physics.ox.ac.uk/instr/HARMONI/) is a visible and near-infrared integral field spectrograph concept, that has been picked as one of two first light instruments at the E-ELT. Oxford Astrophysics is expected to play a leading role in the design and construction of this workhorse first-light instrument, with N. Thatte as Principal Investigator.

This studentship will be funded directly from the STFC HARMONI grant, which has been recently in the news - see the news stories at

The Oxford news website
The Guardian.

Standard STFC studentship criteria will apply.

We are looking for a bright, motivated D.Phil. student to explore, through detailed simulations, a range of science programs that form the key science goals for HARMONI. Through analysis of the resulting data cubes, this project aims to quantitatively demonstrate the “transformational potential” of the E-ELT. In particular, it will explore the sensitivity limits and expected accuracies of observations, folding in diverse parameters such as the adaptive optics performance, instrument specifications and cosmological simulations. It will also study synergies of the proposed observations with other key facilities, such as ALMA or JWST.

For more information, please write to Prof. Niranjan Thatte (n [dot] thatte1 [at] physics [dot] ox [dot] ac [dot] uk).

Designing HARMONI, a first-light instrument for the European Extremely Large Telescope

Supervisor: N.Thatte. Collaborators: M. Tecza, F. Clarke, R. Houghton

The European Extremely Large Telescope (E-ELT, http://www.eso.org/sci/facilities/eelt) will be the world’s largest visible/infrared telescope. With a primary mirror diameter of 39 m, it will have more collecting area than ALL the world’s telescopes built to date. The HARMONI instrument (http://astroweb1.physics.ox.ac.uk/instr/HARMONI/) is a visible and near-infrared integral field spectrograph concept, that has been picked as one of two first light instruments at the E-ELT. Oxford Astrophysics is expected to play a leading role in the design and construction of this workhorse first-light instrument, with N. Thatte as Principal Investigator.

This studentship will be funded directly from the STFC HARMONI grant, which has been recently in the news - see the news stories at

The Oxford news website

The Guardian.

Standard STFC studentship criteria will apply.

We are looking for a bright, motivated D.Phil student with a strong interest in astronomical instrumentation to work on the detailed preliminary design of this instrument. This will include involvement in the conceptual design of one or more of the opto-mechanical assemblies, but will also include laboratory testing of key components / moving mechanisms. There is a wide range of work packages where the student can play a key role, depending on skills and interest. There will also be opportunities to work together with consortium partners in France and Spain.

If you are interested, please write to Prof. Niranjan Thatte (n [dot] thatte1 [at] physics [dot] ox [dot] ac [dot] uk).

Development of next-generation radio receivers and antennas

Professor Mike Jones and Dr Angela Taylor

Over the next few years a new generation of radio telescopes will be built which will transform astrophysics and cosmology. Over the frequency range 50 MHz to 50 GHz, new telescopes will explore the deep Universe in the redshifted bands of hydrogen and carbon monoxide, as well as in radio continuum emission, and the cosmic microwave background itself. In contrast to the small numbers of antennas in traditional radio telescopes, these new instruments will have antennas and receivers numbering between hundreds and tens of millions, which will need to combine extreme performance with the ability to be manufactured cheaply in large quantities. This project will suit a technically-inclined student who is excited by the possibility of designing and building hardware that may end up in some of the world's largest and most capable scientific instruments. Specific possibilities include working on antenna and receiver design for MeerKAT, the South African precursor telescope to the Square Kilometre Array; a new instrument to detect redshifted CO and the Sunyaev-Zel'dovich effect; and the SKA itself, for either its high-frequency dish antennas or the low-frequency aperture arrays. The work itself will include simulation and design work using state-of-the-art electromagnetic CAD tools, construction and testing of prototypes in our laboratories and workshops in Oxford, and field work on overseas sites in South Africa, Australia or the USA.

GALACTICA: the next generation of ab-initio Milky Way simulations

Dr Julien Devriendt and Dr Adrianne Slyz
Project description: Up to now, Milky Way-like (similar mass), dark matter only, halos have been simulated starting from the tiny matter fluctuations detected in the Cosmic Microwave Background radiation (e.g. Via Lactea: www.ucolick.org/~diemand/vl/ and Aquarius: http://www.mpa-garching.mpg.de/aquarius/ projects).
However, we have known for a long time (e.g. book of Binney &Tremaine: Galactic Dynamics, 1989) that baryons dominate the mass budget within the radius of the Sun's orbit. Therefore the goal of this project is twofold: 1/ to upgrade the initial conditions so that they reflect the observed environment of the Milky Way 2/ to add the baryonic physics to the simulations. This will lead to the exciting possibility of performing for the first time a direct comparison with the wealth of observations of the Milky Way neighborhood already available (e.g. SDSS survey: www.sdss.org), as well as making predictions for the forthcoming satellite experiment GAIA (gaia.esa.int). In particular, one of the main goals of the DPhil will be to test the LCDM model using Galactic archeology probes. The work will be carried out in collaboration with a small team of dynamic young researchers led by C. Pichon (IAP, Paris).

Plasma astrophysics of galaxy clusters and accretion discs

Dr A Schekochihin
There are several possible projects under this heading, united by a common general theme: how do plasma microphysics and magnetised turbulence combine to determine the transport properties of cosmic plasmas, which then lead to observed global dynamics? The specific questions include

1. magnetogenesis, i.e. the physical origin of the observed magnetic fields in galaxies and galaxy clusters;
2. the structure of the magnetised plasma turbulence that results once the magnetic fields are strong enough to be dynamically important; nature of kinetic plasma turbulence in phase space;
3. heating of intracluster plasmas via turbulence and thermal stability ("the cooling regulation" problem); ways in which the heating and transport properties of the intracluster medium are determined by plasma instabilities driven by pressure anisotropies spontaneously arising in high-beta plasmas;
4. thermal conduction in tangled magnetic fields (the general physical problem and application to intracluster plasma);
5. heating of ions and electrons in accretion flows; implications for momentum transport.

The projects will involve kinetic theory and numerical simulations of magnetised plasmas, as well as, depending on the student's inclinations, data analysis (solar wind measurements could be used as proxy for astrophysical plasmas). Interested candidates are invited to contact Dr A. Schekochihin for further information (a [dot] schekochihin1 [at] physics [dot] ox [dot] ac [dot] uk)

Projects by Prof James Binney and Dr John Magorrian

A major international observational effort is underway, from ground and space, to reveal the structure, dynamics and history of our Galaxy. Sophisticated dynamical models are key to inferring from massive surveys what is the distribution of the Galaxy's dark matter, and how the Galaxy was assembled. Oxford has developed a new approach to Galaxy modelling and there is much to be done both extending the scope of these models and using them to interpret data. We are heavily involved in the RAVE survey that is gathering spectra of half a million stars from Australia, and will participate in the interpretation of data from the Hermes survey, for which an instrument is now being built in Australia. We plan to play a large role in interpreting data
from ESA's Cornerstone Mission Gaia, due for launch in 2012. We are modelling both stars and gas, and will eventually model the dark matter. Some projects are quite mathematical, others are heavily involved with data.

Project 1. (Prof James Binney)
What's the most effective way of comparing a model with an analytic distribution function to (a) real survey data, and (b) a model galaxy that is the endpoint of a numerical simulation of galaxy formation? How best to detect systematic deviations between the analytic model and the data? How to infer from these deviations how the model needs to be changed?

Project 2. (Dr John Magorrian)
When comparing the predictions of dynamical models against observed stellar surveys, it is important that the effects of the (unknown) dust distribution are included in the models. Moreover, modelling the distribution of dust and
gas will provide complementary information on the structure of the Galaxy. We offer a project tackling the challenging inverse problem of constructing three-dimensional maps of the Galaxy's ISM from existing observations.

Project 3. (Prof James Binney)
Our galaxy is barred and our models are for the moment axisymmetric. What is the most effective way to progress to barred models?

Project 4. (Prof James Binney)
What will be the signatures of spiral structure in Gaia data? Are any signatures present already in ground-based data? How should we exploit these signatures to determine the mass of the disc and thus the mass of the local
dark-matter halo?

Project 5. (John Magorrian)
The standard way to model galaxies is to assume a smooth, static potential and then find the orbit distribution function that, when projected, best matches the observables. Repeat for a range of trial potentials until the best combination of potential and distribution function is found. This project investigates alternative, less well-developed methods in which the potential and distribution function are fit simultaneously (e.g., one such method is to "sculpt" a live N-body model of the galaxy).

Hydrodynamical Modelling of Common-Envelope Evolution and Stellar Mergers

Professor Philipp Podsiadlowski

Common-envelope evolution, where two two stars spiral towards each other inside a surrounding gaseous envelope, is one of the most important, but also one of the least understood phases of binary evolution. The objective of this project is to model this phase using different complementary approaches (combining 1-d stellar hydro calculations with realistic input physics and more approximate 3-d SPH simulations) and to assess the importance of various physical processes (e.g. recombination energy, accretion energy). The goal is to develop realistic physical criteria for the ejection of common envelopes and the merging of the stars with applications to gamma-ray bursts, planetary nebulae and supernova progenitors.

The Fireworks Initiative: Understanding Cosmic Explosions

Professor Philipp Podsiadlowski

This project is part of an international collaboration trying to understand the diversity of cosmic explosions, such as supernovae of various types, hypernovae and gamma-ray bursts, and their implications for the evolution of galaxies and the chemical evolution of the Universe. As part of this project, the student will explore theoretically how various progenitor channels can account for the observed diversity, examining the role of rotation, binary evolution and metallicity. This will involve performing stellar and binary evolution calculations and possibly simulations of whole stellar populations. One of the objectives is to develop observational predictions that can be tested within the framework of the fireworks project.

Pulsars with LOFAR

Aris Karastergiou

Highly stable clocks, distributed around the Galaxy and beyond, pulsars offer the opportunity to conduct extreme experiments in physics on astronomical scales. Pulsars are more massive than the sun, but only ~10km in diameter and with magnetic fields over a billion times stronger than the Earth’s. In the next decade, pulsars are likely to lead to direct detection of Gravitational Waves, opening a new window in astrophysics. To achieve this, new very sensitive radio telescopes are being designed and built (LOFAR, MeerKAT, the SKA) and the physical models that determine the observed rotational stability of pulsars are constantly being improved.

Errors in the modelling of the rotational properties of pulsars arise from intrinsic variability and propagation through the magneto-ionised interstellar medium. This PhD project will use data from LOFAR, the largest radio telescope in the world at frequencies between 30 - 230 MHz, to develop and apply revolutionary new techniques (e.g. cyclic spectroscopy) in modelling and counteracting the effects of the interstellar medium. These techniques, combined with our ever improving modelling of intrinsic rotational stability, will be used to achieve the high timing precision necessary for Gravitational Wave detection in the era of the Square Kilometre Array.

Supernovae and Cosmology

Dr Mark Sullivan and Prof Isobel Hook

Oxford is involved in the Palomar Transient Factory and with major new
survey projects that are due to start in 2012. Many projects
are available using these large datasets, and students would be
directly involved in carrying out follow-up observations at the
telescopes and scientific analyses of the data. Two example projects
are described below.

1. PTF (Palomar Transient Factory) is a highly-successful survey of
the local Universe designed to systematically hunt for nearby Type Ia
Supernovae for future dark energy analyses. The survey has been
running since 2009 and we are carrying out a large observational
follow-up campaign to obtain spectra and multi-epoch light curve
photometry for PTF discoveries. A large amount of data is now hand
including a uniquely large sample of i-band lightcurves. One project
involves analysing the lightcurves and adapting current light-curve
fitting tools to work in the i-band. The student will then use these
tools to analyse new data from the VISTA 4m telescope in Chile that
will measure near-infrared lightcurves of supernovae at intermediate
redshifts (hence sampling the rest-frame i-band). The data and
analysis tools will form an important reference set for future
infra-red supernova surveys for cosmology such as that from ESA's
Euclid mission.

2. PESSTO (Public ESO Spectroscopic Survey for Transient Objects) is a
major new spectroscopic survey, starting in April 2012, that will
generate vast quantities of spectra of nearby supernovae and other
transient objects. Together with corresponding photometric
measurements, these data can be used for studies of Type Ia supernovae
for cosmology, and also for exploring extreme events: ususual
supernovae that provide insight into the physics of their explosion
mechanisms and environments. There will be opportunities for the
student to take part in PESSTO observing runs in Chile.