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| Date | Speaker | Topic |
|---|
August 21
(THURSDAY) |
Alan Duffy
(Swinburne) |
Extra seminar - First Galaxies and DRAGONS |
| One of the most important questions in astronomy today is the source of the ionising photons that caused a predominantly
neutral Early Universe to evolve into the ionised one we see today. I have investigated this Epoch of Reionisation with a
a new suite of high resolution hydrodynamical simulations, created within the DRAGONS group. These simulations show
that the galaxies observed at early times represent merely the tip of an iceberg; with a hidden population of faint galaxies
that can Reionise the Universe with ease. Although the global star formation history of the early universe is strongly
constrained by current observations, we actually know little about the nature of star formation at this time (as given by the
specific star formation rate). I will demonstrate that we can understand these objects but need to push our observations deeper,
a goal that will likely have to await the James Webb Space Telescope. |
August 28
(THURSDAY 2.30pm) |
J.F. Drake
(University of Maryland & UC Berkeley) |
Extra seminar - Voyager crosses the heliopause |
| The heliopause (HP) is the boundary that separates the plasma
environment of the sun from that of the interstellar medium. I will
discuss the recent Voyager spacecraft observations of this outer
boundary and parallel theory and modeling efforts that suggest that
the boundary is much more complex than a simple magnetic field
rotation that separates two disparate plasma regions. Dropouts of
energetic particles produced within the heliosphere and corresponding
increases in the strength of the magnetic field measured by Voyager 1
in 2012 suggested that the spacecraft had crossed the HP. However, the
absence of a corresponding rotation in the direction of the magnetic
field convinced the Voyager science team that the spacecraft remained
within the heliosphere. A parallel modeling effort of the global
heliosphere and local processes at the HP suggested that Voyager 1 had
crossed the HP. This conclusion was confirmed when wave
measurements revealed that the plasma density at Voyager 1 had
dramatically increased above heliospheric values. The present picture
of the magnetic structure of the outer heliosphere and HP is that the
large-scale magnetic field rotates gradually from its interstellar
direction to that of the Parker spiral magnetic field at the
HP. Locally at the HP magnetic reconnection has produced a complex set
of nested magnetic islands leading to a porous HP in which galactic
cosmic rays enter the heliosphere and heliospheric particles can
exit into the local interstellar medium. However, not everyone is in
agreement. There is a significant contingent who are convinced that
Voyager 1 remains within the heliosphere. The reasons for the continued
controversy will be discussed. |
| September 17 |
Shaun Hotchkiss
(Sussex) |
Can we measure the ISW effect of voids? Do they explain the CMB coldspot? (what other cosmology can we do with them?) |
| Both general relativity and the LCDM cosmological model appear to describe our universe quite well. However LCDM, at least, has a number of awkward aspects to it, most especially the existence and magnitude of "dark energy". General relativity is most heavily constrained at large densities. And dark energy only affects regions of the universe once expansion causes their density to drop to a sufficiently low value. Therefore, in an ideal world, the under-dense regions of the universe (i.e. "voids") would be the best place to look for any new cosmological physics. I will discuss how true this is and what will need to be done to make it more true. Special emphasis will be given to the integrated Sachs-Wolfe (ISW) effect and cold spots in the CMB. |
| September 24 |
Annette Ferguson
(Edinburgh) |
The Peripheries of Nearby Galaxies: Dim but not Dull |
| Evidence is mounting for the presence of complex low surface brightness structures in the
outer regions of galaxies. While the most spectacular examples are provided by systems hosting coherent debris streams, the most common examples may be extremely diffuse stellar envelopes. Wide-field imagers on large telescopes are allowing us to quantitatively explore the resolved stellar populations in these components within and well beyond the Local Group. I will highlight some recent results from our work and discuss the insight these outer structures provide on understanding massive galaxy assembly. I will also discuss how we are using deep HST studies of M31's outer regions to probe its evolutionary history in unprecedented detail. |
October 1
(2:30pm) |
Paola Borri |
Schuster Colloquium - Shedding new light on cells with coherent multiphoton microscopy |
| Optical microscopy is an indispensable tool that is driving progress in cell biology, and is still the only practical means of obtaining spatial and temporal resolution within living cells and tissues. Coherent Antistokes Raman Scattering (CARS) microscopy has recently emerged as a new multiphoton microscopy technique. We have developed in our laboratory two home-built CARS microscopes. One of th ese features a single 5 femtosecond Ti:Sa source capable of exciting a wide vibrational range, thus enabling powerful hyperspectral microscopy analysis. Furthermore we have invented and demonstrated a novel imaging modality, based on the resonant Four-Wave Mixing (FWM) of colloidal nanoparticles. Results of this work showed that gold nanoparticles can be used as alternative labels beyond traditional fluorescence by exploiting their resonant FWM, to achieve a novel coherent multiphoton microscopy modality free from background and with a spatial resolution significantly surpassing the one-photon diffraction limit. I will present our latest progress with both techniques and their applications to cell imaging. |
| October 8 |
Christopher J. Conselice
(Nottingham) |
Galaxy Assembly as a New Probe of Cosmology |
| We now have a good understanding of most of the modes of galaxy formation for massive galaxies during the past 10 Gyr based on data from space and ground based telescopes. I will discuss how we can now measure the role of major and minor mergers, star formation and gas accretion in the formation of massive galaxies down to z = 0. This is possible due to new near-infrared Hubble Space Telescope imaging from NICMOS and WFC3 focused on massive galaxies in the distant universe, coupled with spectroscopy and deep imaging at all wavelengths to obtain spectral energy distribution information. I will further discuss how galaxy simulations based on CDM are not able to reproduce the properties of distant galaxies or the characteristics of their observed evolution. I will further show how galaxy formation processes can potentially be used as a method for better understanding cosmological features, including the temperature of the dark matter and the underlying cosmological parameters. |
| October 15 |
Andrew Lyne
(JBCA/JBO Manchester) |
Understanding Pulsar Spin-down |
| One of the most important diagnostics used by pulsar astronomers is the rotational spin-down rate. This provides measurements of the age and magnetic field of the neutron star based upon a simple rotating magnetic dipole model. Hoever, it is clear that the slowdown is clearly more complicated than this. I will discuss the simple model and how recent studies of the Crab and other pulsars reveal the physical processes responsible for the way pulsars slowdown. I will also discuss the nature of timing noise in young pulsars, which we have recently revealed as arising from pulsars switching between two different spin-down rates, each corresponding to a different magnetospheric configuration. |
| October 29 |
— |
Internal Symposium |
November 5
(2:30pm) |
Silvia Resconi
(Munich) |
Schuster Colloquium - High energy neutrinos from the Cosmos? Recent results from IceCube |
| The neutrino observatory IceCube is opening a new observational window to the Universe. IceCube, which has been constructed in the icecap at the South Pole, is taking data since Spring 2011 in full configuration. The first years of data reveled the existence of extremely high neutrinos at the PeV scale. The observed diffuse neutrino flux is with high probability of astrophysical origin. In this talk I will summarize the recent observation and discuss the on-going searches for counterparts. Moreover, prospects in particle physics which concerns the PINGU low energy extension of IceCube will be also discussed.
|
November 7
(FRIDAY, 2pm) |
Danny Price
(Harvard) |
Extra seminar
- Instrumentation to detect the dark ages |
| The
Large-aperture Experiment to detect the Dark Ages (LEDA) is a
new experiment that seeks to detect emission from neutral Hydrogen in the
intergalactic medium before the first stars formed. Detection will
deliver observational constraints on the formation of the first stars
and black holes in the Universe. In this talk, I will introduce the LEDA
instrument at the Owen's Valley Radio Observatory, and how it will be
used to measure neutral Hydrogen radio emission at redshifts of 15-30,
about 100 million years after the Big Bang. I will introduce the
instrumentation that enables our ground-based observations, and the
observation strategy we are using to address calibration challenges. In
particular, I report on the flexible correlator architecture that allows
us to correlate 512 inputs over a 60 MHz band, and the three-state
switched radiometer system we are using for calibration of our
total-power data. |
| November 12 |
Greg Sloan
(Cornell) |
The story of carbon: From carbon stars to aromatic hydrocarbons and fullerenes |
| Spectra from the Spitzer Space Telescope reveal a rich variety of
carbon-rich dust grains in circumstellar environments, from the
asymptotic giant branch to planetary nebulae (AGB to PNe). The
spectra provide a number of clues to how the carbon is processed
in these different evolutionary stages, and how that processing
depends on metallicity. Our studies of the dust around carbon
stars in nearby galaxies reveal no obvious dependence of the
dust-production rate with metallicity, which means that
carbon-rich dust should appear even in primitive galaxies. As
carbon stars evolve into PNe, the carbon-rich dust takes many
strange forms. Polycyclic aromatic hydrocarbons dominate the
dust emission from carbon-rich PNe. Spitzer spectra reveal the
presence of fullerenes in younger PNe. In even younger systems
in transition from the AGB, more fragile aliphatic hydrocarbons
appear. Evidence is building that these aliphatics may produce
the enigmatic 21-um emission feature. |
November 13
(THURSDAY, 1pm) |
Hans Olofsson
(Onsala) |
Extra seminar - ALMA observations of the molecular jets in the proto-planetary nebula HD 101584 |
| TBA |
| November 19 |
Rowan Smith
(Manchester) |
Star Formation Then and Now |
| Star formation has been crucial to the evolution of the Universe from cosmic times to the present day. In this talk I shall first examine the formation of the first Population III stars using simulations of primordial halos. I will then compare and contrast this to star formation in present day spiral galaxies using galactic scale simulations where the chemistry of individual molecular clouds is well resolved. Using such techniques it is possible to get a theoretical estimate of the CO dark molecular gas in the galaxy and the morphology of star forming clouds. Finally, we will zoom into the smallest scales to examine how the filamentary geometry of individual molecular clouds affects the stars that form within them today, and how these structures may appear when observed by ALMA. |
November 26
(2:30pm) |
Maurizio Salaris
(Liverpool John Moores) |
Galactic and extragalactic globular clusters: New views and new major problems |
| In the last decade our view of the stellar populations hosted by globular clusters has changed completely. We now know that probably each Galactic and extragalactic old massive star cluster hosts multiple populations showing characteristic chemical abundance signatures. Given the importance of globular clusters as the fossil record of the early stages of galaxy formation, there has been a large number of investigations aimed at understanding the formation of these multiple populations. I will review the scenarios proposed and highlight their successes and failures. I will also present contradicting constraints coming from the study of young/intermediate age massive star clusters, that are expected to be the counterpart of the progenitors of the present globulars. |
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. |
