2012 admissions
Admissions procedure
Admissions timetable
Astrophysics admissions form
Notes on funding
List of available research
areas/projects
|
|
Astrophysics Group
Graduate Research areas/topics for Oct 2012 entry
The upcoming scientific programme of AP Group is built around six
primary areas. These are in broad terms:
-
Star formation and evolution in our own and nearby galaxies, exploiting
ground-breaking new facilities in ALMA and SCUBA-2, and emerging
capabilities at visible and near-infrared interferometers such as VLTI and
CHARA. Our research spans multiple spatial domains, from AU-sized
scales characterising the processes and products of star formation,
through parsec scales investigating the clouds and filaments where star
formation occurs, to the largest scales of star formation in nearby
galaxies.
-
The investigation of galaxy evolution through the cosmic epochs
by exploiting observations in the millimeter, infrared and
optical bands, obtained at some the major groundbased and space
observatories (e.g. IRAM, ALMA, VLT, Herschel, HST). Our research areas
include the coevolution of star formation and black hole accretion,
the dynamics of high redshift galaxies, the metallicity evolution
and the evolution of the dust properties in galaxies.
These studies exploit samples spanning from galaxies in the local
Universe to the most distant objects known.
-
The development of a test-bed for a new generation of near-infrared array
detectors that promise both read-noise and read-rate improvements of
factors of 5-10 over existing devices. We intend to test the
characteristics of these arrays that are critical to their performance in
interferometric and other high-resolution applications so as to
place us in an
unrivalled position to propose new high-sensitivity instrumentation based
on these arrays for ELTs and long-baseline infrared interferometers.
-
An ambitious and timely programme of experimental cosmology
that addresses themes of structure formation, the evolution of baryonic
gas during galaxy assembly, the tensor-to-scalar ratio during
inflation, and the interplay of magnetic fields and gas in the
intra-cluster medium. We intend to exploit data from ALMA, AMI, EVLA,
e-MERLIN, Planck and SKA pathfinders to achieve our science aims in
these areas. We will capitalise on our expertise in radio and CMB
observations, theoretical modelling and data analysis; in addition we
have collaborations in place which will give us access to complementary
data sets in other wavebands.
-
A complementary programme (to our observational work) in
theoretical cosmology. This theme addresses the confrontation of
theoretical predictions with experiment, and the best way to carry this
out, as well as original work in fundamental aspects of cosmology and
gravitation. Current and planned work includes comparison of
cosmological models and data sets using Bayesian evidence; tests of
predictions from modified gravity theories and studies of inflation
using data from the Planck satellite.
-
A new programme, linked with the cosmological work, concerning modelling
of the generation, propagation and detection of gravitational waves (GW)
through the proper general-relativistic description of the energy and
momentum carried by GW, and the development and application to real data
of Bayesian methods for detecting GW signatures in laser-interferometer
experiments such as LIGO and the forthcoming LISA.
Please note that this year we do not have any projects
available with Dr Peter Duffett-Smith in the area of "Radio propagation
and positioning systems".
Details of possible topics available within our active areas of
research for graduate students commencing in October 2012
are listed below, where the ordering of the areas in the list is random.
In each case there is list of staff members working in the area, a brief
description of their research, followed by further information on possible
topics for graduate projects that might be available.
Please note that these summaries provide only a snapshot and overview
of the broad research areas undertaken by staff in the group. As such they
are liable to change, and so you may wish to revisit these pages in early
2012, and closer to the deadline for applications in February 2012.
If you are interested in applying for technical projects with
the Detector Physics Group, you are advised to contact Professor
Stafford Withington directly at stafford "at" mrao.cam.ac.uk to
obtain details of his group's opportunities this year.
Astrophysics Group PhD Research areas/topics for October 2012
entry
Star formation and
evolution
Our research in this area will be structured in three different major
areas.
-
Staff members: David Buscher, Chris Haniff - dfb, cah@mrao.cam.ac.uk
Exploiting visible and near-infrared interferometer arrays to test and
validate models of star formation and stellar evolution, through studies
of pre-main-sequence multiplicity and the determination of high precision
masses and radii of young, giant and metal-poor stars.
Most solar-type pre-main sequence (PMS) stars are observed to be binary or
higher order multiple systems yet the mechanism of pre-stellar core
collapse to form single or multiple systems remains poorly understood. The
observed multiplicity of stars, at birth, and as a function of age, is a
powerful diagnostic of the mechanisms that influence star formation. A
goal of this project will be to determine the multiplicity fraction of PMS
stars in the hitherto unexplored separation range (0.3--8~AU) using
near-infrared interferometers which have angular resolutions of order a
milliarcsecond. Fewer than ten binary candidates have been discovered
with orbital separations as small as this in nearby star forming regions,
as compared to the many hundreds known with separations greater than 10
AU.
This project would suit a student with an interest in star formation who
wishes to undertake observational and interpretational work using the
current generation of long baseline optical and infrared interferometers
(VLTI, CHARA, NOI), as well as parallel observations with other
facilities.
-
Staff members: TBD, TBD - tbd, tbd@mrao.cam.ac.uk
Utilizing the high resolution available with ALMA, and the wide-field
capabilities of SCUBA-2 and HARP, we will study the physics and chemistry
of star formation on a range of physical scales from cluster formation
through to the inner regions of protostellar discs.
This entry will be updated soon.
-
Staff members: TBD, TBD - tbd, tbd@mrao.cam.ac.uk
ALMA studies of the molecular content of interacting galactic systems and
high-resolution studies of a sample of nearby galaxies.
This entry will be updated soon.
Galaxy evolution
Our research in this area will be structured in two different major
areas.
-
Staff members: Roberto Maiolino, Paul Alexander - rm665, pa@mrao.cam.ac.uk
We will use multiwavelength data from space and groundbased observatories
to study the host galaxies of Active Galactic Nuclei in the local Universe
and at high redshift, with the goal of investigating the mutual effects of
galaxy formation and black hole accretion through the cosmic epochs.
The tight relation between Black Holes and spheroids masses in their host
galaxies, along with the similar evolution of star formation and black
hole accretion (AGN activity) through the cosmic epochs, indicate that the
evolution of galaxies and their supermassive black holes are intimately
related. However, the physical mechanisms responsible for this
co-evolution are not yet understood. The goal of this project is to shed
light on the physical mechanisms regulating the coevolution of black hole
growth and galaxy assembly, by exploiting multiwavelength observations of
AGN host galaxies spanning a wide redshift range. More specifically:
-
We will investigate the star formation activity and the stellar population
in AGN host galaxies by exploiting Herschel far-IR data, HST near-IR/optical
images and SINFONI-VLT 3D-spectra. These data will allow us to determine
the evolutionary stage of the host galaxies of AGNs experiencing different
levels activity and with different BH masses, to locate them on
the BH-sigma relation, and to compare the results with models
of galaxy evolution.
-
We will use IRAM, ALMA, SINFONI and X-shooter VLT spectra to investigate
the dynamics of the gas in the host galaxy of
local and high redshift AGNs, by exploiting molecular and ionized gas tracers.
Within this context the main goal is to search
for, and characterize, large scale AGN-driven outflows, tracing the long sought
AGN-feedback that, according to most models, should regulate star
formation in the host galaxies.
-
Staff members: Roberto Maiolino, Paul Alexander - rm665, pa@mrao.cam.ac.uk
We will investigate the driving mechanisms of galaxy formation through
the cosmic epochs, by studying the dynamics of high redshift galaxies,
along with their content of metals and dust. This study will be achieved
by combining far-IR observations from the Herschel Space Observatory,
near-IR 3D-spectra taken at the VLT, and mm/submm data obtained at IRAM
and ALMA.
What is the dominant mode of galaxy formation? Violent, on short
time scales, driven by galaxy merging, or smooth, on long time scales,
regulated by secular processes? What is the role of metal rich
galaxy outflows and pristine gas inflows during galaxy evolution?
These are some of the key, open issues of modern astrophysics. We
will investigate various physical properties of distant galaxies, spanning
a wide redshift interval, to make substantial progress in this field.
More specifically, these issues will be tackled through the following
observational approaches:
-
We will use optical, near-IR and millimetric spectroscopy to trace
the kinematics of the ionized and molecular gas in local and high redshift
galaxies, mostly selected through the the Herschel
Space Observatory. This information will be used to investigate the
dynamical status of these galaxies (merging versus regular disk rotation)
and to reveal the presence of massive outflows, which would reveal the
negative feedback self-regulating star formation, widely invoked by models.
-
We will use the optical and near-IR spectra (mostly from VLT SINFONI and
X-shooter data) to measure the metallicity and chemical abundances,
as well as Herschel and mm/submm ground based data to measure the dust
content, in high redshift galaxies. Chemical enrichment and dust content
are powerful diagnostics of the star formation history in galaxies and,
in particular, provide crucial information on the integrated star formation,
on the time scale of star formation and on the role of gas outflows and
inflows. By measuring these quantities for different classes of galaxies
at different redshifts it will be possible to provide tight constraints
on the galaxy formation processes over the cosmic times.
Near-infrared array detectors
Our research in this area will be structured in a single major
area.
-
Staff members: David Buscher, Chris Haniff - dfb, cah@mrao.cam.ac.uk
The sensitivity of near-infrared interferometric imaging is strongly
determined by the read noise of high-frame-rate detectors. Newly-developed
HgCdTe arrays based on on-chip electron avalanche amplification offer
read-rate and read-noise advantages of factors of 5-10 over existing
arrays. This project will involve building a lab-based interferometric
test-bed to investigate how these detectors can best be used for imaging
of substantially fainter astrophysical targets than currently accessible.
The experience gained from developing and operating this testbed will give us a
worldwide competitive advantage in near-IR instrumentation for
high-angular-resolution imaging, and will allow us to make quantitative
predictions of system performance for new instrumentation. Based on the results
obtained as the project progresses we hope to develop the design of a next
generation optical/infrared interferometric beam combiner.
Experimental & theoretical cosmology
Our research in this area will be structured in four different major
areas.
-
Staff members: Keith Grainge, Anthony Lasenby, Mike Hobson,
Richard Saunders - kjbg1, anthony, mph, rdes@mrao.cam.ac.uk
We have a strong involvement in Planck, and aim to use Planck data in
conjunction with other experiments in order to (a) exploit the Planck SZ
cluster catalogue for astrophysics and late-time background cosmology; and
(b) constrain the amplitude of relic gravitational waves from inflation
through measurements of the B-mode polarization.
The Planck SZ cluster catalogue will provide a unique all-sky sample of
clusters of galaxies selected via their Sunyaev-Zeldovich properties. The
Planck resolution is comparatively low however, for cluster work, and
combining the Planck data with higher resolution data from the Arcminute
Microkelvin Imager (AMI) at Cambridge is a powerful probe of the
properties of the gas distribution and temperature. We will exploit this
data, as well as lensing data and other data where available, for
increased astrophysical understanding of the cluster environment and for
use in samples which constrain cosmological parameters and rates of growth
of perturbations via cluster abundance and mass/temperature scaling
laws.
We are also involved in the QUIJOTE experiment sited in Tenerife, which
will provide detailed maps of the northern sky at frequencies from 11 to
44 GHz, and we aim to exploit these in conjunction with Planck
polarization data in order to set constraints on the B-mode contribution
in CMB perturbations laid down at inflation. These are direct indicators
of the amplitude of gravity waves at this epoch, and detection of them
would be extremely important in constraining inflationary dynamics and
theories.
-
Staff members: Paul Alexander, Keith Grainge - pa, kjbg1@mrao.cam.ac.uk
Galaxy clusters are the largest bound structures in the cosmic web of
matter in the Universe and our group studies their physics and
cosmological evolution using a variety of techniques at radio wavelengths.
We use AMI, the Arcminute microkelvin imager telescope at our radio
observatory to study clusters using the Sunyaev-Zel'dovich effect. This
tells us about the overall matter and temperature distribution in a
cluster.
We can also probe the magnetic field inside clusters by measuring the
degree of Faraday rotation of polarised background sources using the
technique of Rotation Measure (RM) synthesis.
By building up a significant sample of galaxy clusters studied with these
techniques and using data at other wavelengths we gain insight into how
the properties of galaxy clusters change with redshift, which tests
theories of galaxy merger and magnetic field development.
RM synthesis is a challenging topic but one where huge advances should
be possible in the coming few years as new radio telescopes come on line.
In the medium term we are working with the MeerKAT telescope project to
develop their RM synthesis pipeline. The algorithms that we generate for
MeerKAT should be transferable to the Square Kilometre Array telescope
pipeline in the future.
-
Staff members: TBD, TBD - tbd, tbd@mrao.cam.ac.uk
We are aiming on building on our extensive expertise with ALMA, the SKA
and SKA pathfinders coupled with our proven Bayesian analysis skills to
develop a programme around the key cosmological problems to be
addressed by the new generation of radio interferometers -- the
evolution of neutral and molecular gas from the epoch of reionization
to the present and the nature of the first galaxies and AGN.
This entry will be updated soon.
-
Staff members: Anthony Lasenby, Mike Hobson - anthony,
mph@mrao.cam.ac.uk
The theoretical cosmology sub-group work on topics in theoretical
cosmology and astrophysics, as well as on advanced data analysis
methods for cosmology. The active areas of research span inflationary
cosmology to novel neural network methods. A common theme is the
confrontation of theoretical predictions with experiment, and the best
way to carry this out. Among the topics of current interest
are:
-
Evidence-based comparison of cosmological models and data sets: Within a
Bayesian analysis framework, a measure of the probability of a particular
model given the data is available, which is able to penalise models which
have more degrees of freedom than needed by the data. In this way a
quantitative version of Occam's Razor is introduced. We have been
applying this recently to comparison of a novel closed universe model with
available data, and also to ab initio reconstruction of the primordial
power spectrum of perturbations. Future applications will include
reconstruction of the expansion history of the universe, to test models
for dark energy, and to the late time thermal history of the universe as
revealed by CMB and other data.
-
Tests of predictions from modified gravity theories: There has recently
been a great expansion of interest in theories of gravity which attempt to
explain either dark energy of dark matter, or both, within a framework of
modifications to the Lagrangian for gravity. We are interested in this
both from the fundamental physics point of view, and also from the point
of view of testing such theories using current and future data, in which
Bayesian evidence will be a powerful tool.
-
Tests of inflation using data from the Planck Satellite: From January
2013 the first cosmological data from the Planck Satellite will be
released. We are interested in tests of the mechanisms of inflation using
this data, which will be the most informative yet in terms of restricting
possible models of inflation. For example, the novel closed universe model
mentioned above makes detailed predictions for the slope of the spectrum
of perturbations at both large and small scales, which differ from a
conventional power law, and more detailed numerical modelling of the form
of spectrum expected will be an important component of testing this and
other non-standard models.
Gravity wave astrophysics
Our research in this area will be structured in two parallel areas.
-
Staff members: Mike Hobson, Anthony Lasenby -
mph, anthony@mrao.cam.ac.uk
Theoretical work, targeted at localisation of the
energy-momentum carried by such waves. The development of a physically
meaningful description of the energy-momentum of a gravitational wave
within General Relativity has long been an outstanding problem, and in
a series of papers (Butcher, Hobson, Lasenby, 2010, Phys. Rev. D. 82,
104040) we have addressed this problem in
a way which aids not just theoretical understanding, but also enables a
direct picture of how energy and angular momentum is interchanged with
the measuring apparatus in the process of GW detection.
-
Staff members: Mike Hobson, Anthony Lasenby - mph, anthony@mrao.cam.ac.uk
We are exploring advanced data analysis methods for gravitational wave
detection. These centre on Bayesian techniques for template detection in
gravitational wave signals in which there may be multiple sources of both
signal and noise. The methods are being currently applied to real data
from the LIGO Consortium (of which we are a member), and to data simulated
using the characteristics of the forthcoming LISA space mission. By
employing advanced sampling techniques, and the methods of Bayesian
evidence, we are able to achieve state-of-the-art results in the detection
process.
Last modified: 12 December 2011
|
