Extra seminars, which can be organised by anyone in the group separately from the colloquium series, are also included on this page for convenience.
To view a talk abstract, click on the talk title. Click again on the talk title to hide the abstract.
| Date | Speaker | Topic |
|---|
December 3
(2:30pm) |
Chris Lintott
(Oxford) |
Schuster Colloquium - The Zooniverse |
| TBA |
| December 10 |
Scott Ransom
(NRAO) |
But wait! There's more!: A Wealth of Science from Millisecond Pulsars |
| Pulsars are some of astrophysics' most exotic objects. We currently know of about 2300 pulsars in our Galaxy, but a small subset of them, the millisecond pulsars (MSPs), are truly remarkable. These systems are notoriously hard to detect, yet their numbers have more than doubled in the past 4 years via surveys using the world's most sensitive telescopes. Specialized "timing" observations of these new systems as well as much improved monitoring of previously known MSPs are providing fantastic results. Some examples include unusual aspects of binary and stellar astrophysics, the nature of matter at supra-nuclear densities, and the direct detection of gravitational waves, possibly within the next 5 years. |
| January 21 |
Cormac Purcell
(University of Sydney) |
Additional Seminar: Probing the Galactic Magnetic Field using the Gum Nebula
|
| The Gum Nebula is 36 degree wide shell-like
emission nebula at a distance of only 450 pc. It has been hypothesised to be an old supernova remnant, fossil HII region,
wind-blown bubble, or combination of multiple objects. Here we investigate the magneto-ionic properties of the nebula and its
impact on the ISM using data from recent surveys: radio-continuum data from the NRAO VLA and S-band Parkes All Sky Surveys, and
H-alpha data from the Southern H-Alpha Sky Survey Atlas. By analysing rotation measures through the nebula and by fitting a simple
model, we are able to measure the geometry and strength of the ordered magnetic field. The fitted compression factor at the edge of
the nebula strongly constrains its likely origin for the first time. The nebula is also useful as a probe of the magnetic field on
parsec scales and the fitted value of local magnetic pitch-angle represents a significant deviation from the median orientation on
kiloparsec scales. I discuss the implications for Galactic structure and plans for expanded analysis in the era of the SKA.
|
| January 28 |
Gary Fuller
(JBCA Manchester) |
Peering into the Dark: Infrared Dark Clouds and Massive Star Formation |
| Massive stars are important drivers of both
the physical and chemical evolution of galaxies. Understanding their formation is key to understanding phenomena as diverse as the
properties of circumstellar disks, and frequency of planets, in stellar clusters to the origin of pulsars and gamma ray bursts.
However, as a result of their rapid evolution and their prodigious energy output, massive stars quickly dominate their
environments, masking the initial conditions of their formation.
Infrared dark clouds (IRDCs) are dense clouds of dust and gas seen in absorption against the diffuse infrared background in the
galactic plane. As regions not yet dominated by star formation, IRDCs are important targets to study of how dense gas evolves to
form massive stars and identify the initial conditions for massive star formation. Drawing on a large catalogue of IRDCs, the
Spitzer Dark Cloud (SDC) catalogue, constructed using the Spitzer GLIMPSE data, I will discuss a range of recent results which shed
light on the physical processes involved in the formation of massive stars. This will include a discussion of two very different
examples of filamentary IRCDs. One of these contains the most massive protostar known in our galaxy while the other shows a
remarkable kinematic structure. I will then move on to describe the properties of a new sample of larger scale filamentary groups
of clouds identified in the SDC catalogue. Finally I will describe current work using Hi-GAL, the Herschel galactic plane survey,
to identify the protostars and pre-stellar clumps within SDCs and the initial follow-up of a sample of high mass pre-stellar
clumps. |
February 4
(2:30pm) |
Colin Humphreys
(University of Cambridge) |
Schuster Colloquium -
How Gallium Nitride can save energy and carbon emissions, and improve exam performance! |
| The 2014 Nobel Prize for Physics was awarded to
three Japanese scientists for the invention of blue light-emitting diodes made from gallium nitride (GaN). This talk will describe
collaborative research between Manchester and Cambridge which has built upon this Nobel Prize winning work. In particular, we have
solved the mystery of why GaN LEDs are so bright when the defect density of the GaN is so high. We have also shown how to reduce
substantially the cost of LEDs for lighting, and low-cost LEDs based on our technology are now being manufactured in the UK by
Plessey. These low-cost LEDs should enable their widespread use, resulting in substantial savings of electricity and carbon
emissions. GaN is also useful for low-energy power electronic devices as well as low-energy lighting, and GaN has the potential to
save 25% of all the electricity we use. Optimised LED lighting can improve our health and even improve exam performance! |
| February 11 |
Moira Jardine
(St Andrews) |
The Space Weather of other Suns |
|
"Space Weather" describes the impact that the Sun has on its environment
through the magnetically powered flares, mass ejections and wind that it
produces. Although the Sun is a relatively inactive star, the impact of a
large solar mass ejection can damage satellite electronics, shut down
terrestrial power grids and disrupt radio communications. On more active
stars, we might expect even more dramatic space weather and a greater
impact on any orbiting planets. In this talk I will describe how we can
use observations that reveal the geometry of stellar magnetic fields to
understand the nature of the accompanying space weather.
|
February 13
(11:00am) |
Jens Chluba
(IoA, Cambridge) |
Additional Seminar: Science with CMB Spectral Distortions |
|
Since COBE/FIRAS we know that the CMB spectrum is extremely
close to a perfect blackbody. There are, however, a number of
processes in the early Universe that should create spectral
distortions at a level that is within reach of present day
technology. I will give an overview of recent theoretical and
experimental developments, explaining why future measurements of the
CMB spectrum will open up an unexplored window to early-universe and
particle physics, with possible non-standard surprises but also
guaranteed signals awaiting us. I will also highlight the
complementary of the distortion signals and the CMB anisotropies,
showing that future distortions measurements will shed new light on
different inflation models.
|
| February 25 |
Alastair Edge
(Durham) |
The Rise and Fall (and Rise again!) of NGC1275 |
| NGC1275/3C84 has held a central role in the long-running
saga of cooling flows and AGN Feedback. On the face of it, NGC1275
is a very unusual elliptical galaxy with atypical radio properties.
However, on closer inspection it shares many characteristics with
the central galaxies in other cooling flow clusters. I will concentrate
on the multi-wavelength variability of NGC1275 and discuss its
implications for our understanding of AGN Feedback in clusters. |
March 4
(2:30pm) |
Val Gibson |
Schuster
Colloquium
- Fruitful flavour at
the Large Hadron Collider |
| TBA |
March 11
(2:30pm) |
Stephen Padin
(Caltech) |
Schuster Colloquium - Prospects for far-infrared surveys |
| Enormous progress has been made in far-infrared detector arrays over the past two decades, and we will soon be able to build imaging sensors with 100,000 pixels. The new sensors, on a 30-50m diameter, wide-field telescope, at a good observing site, will provide unprecedented survey speed, giving enough sensitivity and sky coverage to find typical dusty galaxies at high redshift. New, far-infrared surveys will be able to measure the star formation rate for dusty galaxies over cosmic time. Such measurements are critical for understanding the origin of dusty galaxies and how they came to dominate during the peak epoch of star formation. Far-infrared surveys present significant technical challenges in detectors, readout electronics, wide-field telescopes, and coupling optics. I will explain how these challenges are being met, and describe prospects for far-infrared, multi-object spectrometers that will measure redshifts and physical conditions for large numbers of galaxies.
|
| March 18 |
Richard Hills
(Cambridge) |
How ALMA came to be |
| This talk will be a personal
retrospective of some of the events that led up to the creation of ALMA, together with some discussion of the scientific and
technical advances that occurred along the way. Topics that I plan to talk about include the prehistory, which provided the
scientific case for building a large millimeter-wave array, the international aspects, including the site selection, and the
choice of the basic parameters of the design. I will then cover some aspects of the development, construction and
commissioning program and show a few recent results. If time permits then I could indulge in some speculation about future
developments. |
| April 15 |
Ignas Snellen
(Leiden) |
Finding extraterrestrial life using ground-based high-dispersion spectroscopy |
| The cancellation of both the
Terrestrial Planet Finder and Darwin missions means that it is
unlikely that a dedicated space telescope to search for biomarker
gases in exoplanet atmospheres will be launched within the next 25
years. In this talk I will advocate that ground-based telescopes
provide a strong alternative for finding biomarkers in exoplanet
atmospheres through high-resolution transit observations. I will
review some of the exciting result we have recently obtained on
hot-Jupiter atmospheres, and will show what can be done with the
planned E-ELT. |
April 22
(2:30pm) |
Ray Goldstein
(DAMPT, Cambridge) |
Schuster
Colloquium - Synchronization of Cilia |
| TBA |
| April 29 |
Daisuke Kawata
(MSSL/UCL) |
Spiral arms in numerical simulations of disc galaxies |
| Using N-body simulations of Milky Way-sized barred spiral galaxies, we demonstrate that the simulated galaxy shows a co-rotating spiral arm, i.e. the spiral arm rotates with the same speed as the circular speed. We find that the stars tend to rotate slower (faster) behind (at the front of) the spiral arm and move outwards (inwards), which causes the significant radial migration. We discuss the observational consequence of such radial migration, and the observabilities of the systematic stellar motion around the spiral arm, taking into account stellar population and the dust extinction. |
| May 6 |
Janet Drew
(Hertfordshire) |
Surveying the optical Galactic Plane at 1 arcsec resolution |
| The talk will begin with a summary and status update of the EGAPS surveys, IPHAS, UVEX and VPHAS+, pointing out the ways in which
these surveys complement the expected yield from Gaia. Contrasting science applications will then be reviewed -- namely (i) their use for
3D extinction mapping, (ii) the automatic selection of various types of massive star, (iii) testing models of the disc of the Milky Way via star counts. |
| May 13 |
Debora Sijacki
(Cambridge) |
How to model AGN in cosmological simulations? |
| Hydrodynamical cosmological simulations are one of the most powerful tools to
study the formation and evolution of galaxies and their central black holes in the fully non-linear
regime. Despite several recent successes in simulating Milky Way look-alikes,
self-consistent, ab-initio models are still a long way off. In this talk I will
briefly review numerical and physical uncertainties plaguing current state-of-the-art
cosmological simulations of galaxy formation. I will then present global properties of
galaxies and black holes as obtained with novel cosmological simulations, the so-called Illustris
project, and discuss which feedback mechanisms are needed to reproduce realistic stellar
masses and galaxy morphologies in the present day Universe. In the second part of the talk
I will discuss novel ways how to model AGN physics on small scales and how to incorporate
these methods in large-scale cosmological simulations. |
| May 20 |
Serena Viti
(UCL) |
Determining the physical and chemical conditions of AGN and starburst
galaxies |
| It is now well established that chemistry in external galaxies is rich
and complex. In this talk I will show how molecular emission from
AGN/starburst galaxies can be used to explore and characterize the
physical conditions and energetics of these galaxies, as well as,
possibly, their evolutionary status. I will present examples of the
chemical and radiative transfer models that have been developed in
recent years to tackle the often unresolved (spatially and spectrally)
extragalactic molecular emission. I will then show recent applications
of such models in nearby galaxies and how to make molecules into
powerful diagnostics of the evolution and distribution of molecular gas. |
| May 27 |
Douglas Scott
(UBC) |
New results from Planck |
| The Planck satellite has completed its mission to map the entire microwave sky at nine separate frequencies. A new data release was made in February 2015, based on the full mission, and including some polarization data for the first time. The Planck team has already produced more than 100 papers, covering many different aspects of the cosmic microwave background (CMB). We have been able to learn in detail about the physics of the interstellar medium in our Galaxy, and to remove this foreground emission in order to extract the cosmological information from the background radiation. Planck's measurements lead to an improved understanding of the basic model which describes the Universe on the very largest scales. In particular, a 6 parameter model fits the CMB data very well, with no strong evidence for extensions to that sceneraio. There are constraints on inflationary models, neutrino physics, dark energy and many other theoretical ideas. New cosmological probes include CMB lensing, CMB-extracted clusters of galaxies, the Cosmic Infrared Background and constraints on large-scale velocities. This talk will highlight some of the new results of the 2015 papers, including the improvements coming from the addition of the polarization dimension.
|
May 29
(Friday) |
Douglas Scott
(UBC) |
Additional Seminar: Statistics of deep radio counts |
| The obvious way to estimate the areal density of sources is by counting them, but actually it's much better not to count sources at all, but instead to perform a careful statistical analysis of the 1-pt function of the image. There is lots of confusion about this P(D) approach. I'll try to explain our group's analysis methods, particularly for 3GHz VLA data with an rms of 1microJy, which enables us to estimate counts below the 100nJy level. |
