Recent Highlights in Asteroseismology: a Biased Selection
By Professor Conny Aerts, University of Leuven, Belgium
3rd May 2006
In this talk we take an overview of some of the recent achievements in the field of asteroseismology. We discuss four case studies: solar-like oscillators, red giant pulsators, and two kinds of massive main sequence B-type stars. For each of them, we show modern data and interpret them in terms of stellar evolution models. We summarize the shortcomings of the latter and point out how the agreement between data and theoretical models could be improved.
By Dr Carolina Odman, Sterrewacht Leiden, Netherlands
23rd May 2006
Universe Awareness is a new programme aimed at chikdren between 4 and 10 years of age in economically disadvantaged environments and developing countries. Universe Awareness is motivated by the premise that access to simple knowledge about the Universe is a birth right. The ages of 4 to 10 years are crucial in the development of a value system. At that age children can appreciate the beauty of astronomical objects and can develop a feeling for the vastness of the Universe. Exposing young children to such material is likely to broaden their minds and stimulate their world-view. A successful pilot project has taken place in Venuzuela. From spontaneous observations of the sky in remote locations to teacher-training workshops in the Centro de Investigaciones de Astronomi in Merida, this was a wonderful experience for participants and organisers alike. It provides a glimpse of how successful the Universe Awareness programme can be.
Evolution of Dwarf Irregular Galaxies: The case of NGC 6822
By Dr Leticia Carigi, UNAM, Mexico
25th May 2006
Based on the photometric properties of NGC 6822 we derive a robust star formation history. Adopting this history we compute a model of galactic chemical evolution. The model matches the present-day chemical and photometric properties. The dark halo mass evolves according to the mass assembly history predicted by a Lambda-CDM cosmology. We model the evolution of the baryonic mass aggregation history in this cosmological context assuming that part of the gas available for accretion never falls into the system due to reionization. The model requires an early outflow and a lower upper mass limit for the IMF than that of the solar vicinity, in agreement with recent results.
6dFGS, 2MASS and SuperCOSMOS: Towards a consistent picture of stellar populations in local galaxies
By Dr Rob Proctor, Swinburne University, Australia
21st June 2006
We present results of the analysis of Lick indices in ~7000 6dF Galaxy Survey spectra. Ages and metallicities are derived for the central regions of galaxies of all morphological and emission types. These data are compared to the global photometry of 2MASS and SuperCOSMOS, from which we calculate B, R and K band mass-to-light ratios. These are used to investigate the relationship between the central properties, as indicated by our spectroscopic analysis, and teh global properties, as indicated by the photometry. This combination allows us to go some way towards breaking the age-metallicity-burst strength degeneracy that has limited previous studies.
Mass, Metallicity, Kinematics and Star Formation in Galaxies at z=2
By Dr Dawn Erb, Harvard, USA
19th July 2006
The redshift interval 1.5 to 3 hosted a large fraction of the assembly of stellar mass in the universe and the peak of AGN activity, but the quantitative study of galaxies in this redshift range from large spectroscopic samples has only recently become feasible. I will discuss the results of a large H-alpha survey of star-forming galaxies at z~2, including kinematic properties inferred from line widths and spatially resolved emission, star formation rates, evidence for galactic-scale outflows, and the comparison of stellar, dynamical and inferred gas masses. The galaxies show a strong correlation between stellar mass and gas phase metallicity (the first detection of the mass-metallicity relation in star-forming galaxies at high redshift), which is best explained by a model in which galaxies of all masses lose gas to outflows at a rate higher than the star formation rate.
Future Directions in Astronomy Visualisation
By Dr Chris Fluke, Swinburne, Australia
9th August 2006
Every year, astronomers spend millions of dollars on telescopes, instruments and computers, yet they tend to look at the resulting data on small, flat, two-dimensional displays. Limiting factors seem to be the level of awareness of techniques that are available, and access to appropriate software tools to simplify the visualisation process. I aim to address both of these issues. I will present a summary of Swinburne’s work on advanced image displays including stereoscopic projection and MirrorDome (full-dome digital projection on a budget). I will also demonstrate S2Plot: a new, 3-dimensional plotting library with support for both standard and advanced display devices. With a PGPlot-inspired interface, S2Plot provides astronomers with elegant techniques for displaying and exploring 3d data sets directly from their program code.
Multi-Wavelength Studies of the Galaxy Formation with GCD+
By Dr Daisuke Kawata, Carnegie Observatories
24th October 2006
We present our recent studies of galactic chemodynamics with our original galactic chemo-dynamical evolution code, GCD+ (Kawata & Gibson 2003). First, we demonstrate that the self-regulated AGN heating is crucial to explain the multi-wavelength properties of observed elliptical galaxies (Kawata & Gibson 2005, MNRAS, 358, 16). Next, a thick disk formation senario suggested by our numerical simulations (Brook et al. 2004, ApJ, 612, 894) is explained. Finally, we introduce our dwarf speroidal galaxy formation study (2006, ApJ,641,785).
The ABC of dEs : First Results from the MAGPOP-ITP
By Dr Dolf Michielsen, University of Nottingham
23rd November 2006
Although dwarf elliptical galaxies (dEs) are the most abundant type of galaxy in nearby clusters, we still don’t understand fully how they formed and what mechanisms govern their evolution. In the framework of an International Time Programme (ITP), the European MAGPOP Network started a survey of dwarf galaxies in the Virgo cluster and the field, using 70 nights of telescope time on the 4 large telesocpes in La Palma. Here I report the first results of the optical spectroscopy of 25 dEs. The dEs are younger than normal elliptical galaxies, contradicting common belief that they are relics from the hierarchical structure formation. They are also metal-poor and show an alpha/Fe underabundance. This implies that dEs experience prolonged star formation and metal-enhanced winds.
Updating the Earth’s Ozone by Going Backwards in Astronomy
By Dr Elizabeth Griffin, NRC-HIA-DAO
27th November 2006
Ground-based observations of the stars unavoidably include information about the Earth’s atmosphere. Research I have been conducting in Canada lately is an investigation of evidence for the relatively recent evolution of the Earth’s ozone layer, as measured from historic stellar spectra observed during the 20th century.
The Hot Gas in Normal Elliptical Galaxies: Evidence for AGN-Feedback
By Dr Steven Diehl, Los Alamos National Laboratory
13th September 2007
I present a complete morphological and spectral X-ray analysis of the hot interstellar medium in 54 normal elliptical galaxies in the Chandra archive, completely isolating their hot gas emission for the first time. A comparison with optical images and photometry shows no correlation between optical and X-ray ellipticity, contrary to expectations for hydrostatic equilibrium. Instead, we find that the gas in general appears to be very disturbed and that the amount of asymmetry strongly depends on radio and X-ray AGN luminosities, such that galaxies with more active AGN are more disturbed. Surprisingly, this AGN–morphology connection persists all the way down to the weakest AGN, providing strong morphological evidence for AGN feedback similar to clusters even in normal elliptical galaxies. We also find evidence for the central AGN influencing the inner temperature profiles of these systems as well. We conclude that the hot gas in elliptical galaxies is generally not in hydrostatic equilibrium; instead, it is continually disturbed and most likely heated by intermittent outbursts of the central AGN.
Linking black hole growth and recent star formation history in the local Universe
By Dr Vivienne Wild, MPA
11th October 2007
A popular model for the coevolution of bulges and supermassive black holes is one in which a galaxy merger leads to the inflow of gas which fuels a strong starburst, followed by an AGN phase in which the black hole grows significantly. I will present and discuss recent results from the SDSS spectroscopic galaxy catalogue, which use a new, high signal-to-noise ratio spectral diagnostic of recent star formation history, to show that the majority of low redshift black hole accretion in Type II AGN occurs under less spectacular circumstances. However, a small number of galaxies
(less than 10% of our sample of ~34000) which are undergoing, or have recently undergone, a major star formation episode, have the highest average black hole growth rates and show evidence for recent strong interactions and mergers in their light distributions. A significant fraction of this black hole growth occurs in AGN with high amounts of dust extinction, often coinciding with an old, post-starburst stellar population.
Is Downsizing Universal? Stellar Populations in the Coma Cluster
By Dr Scott Trager, Groningen
18th December 2007
Observations of red-sequence galaxies in both the local and high-redshift Universe and hierarchical galaxy formation models make firm predictions for the stellar populations of elliptical and S0 galaxies (early-type galaxies or ETGs). Three of the most robust are (1) ETGs of a given stellar mass form stars earlier and thus should have older stellar population ages in the highest-density environments than those in lower-density environments; (2) the most-massive ETGs in the densest environments should have a small spread in stellar population ages, and (3) in all environments, smaller ETGs should have younger stars (`downsizing’). To test these predictions, I present stellar population parameters of twelve elliptical and S0 galaxies in the Coma Cluster around and including the cD galaxy NGC 4874, based on spectra obtained using the Low Resolution Imaging Spectrograph on the Keck II Telescope. I extend the sample with literature data to study trends with velocity dispersion and mass. I show that ETGs in the Coma Cluster violate predictions (1) and (3) — and therefore Coma Cluster galaxies appear younger at all ages than field galaxies and do not appear to show `downsizing’. These results may raise interesting problems with current models of galaxy formation.
After an introduction on massive rotating stars, I will present recent results on the evolution of the first stellar generations. I will discuss the importance of rotationally induced mixing and mass loss at very low metallicities and their implications concerning chemical enrichment in the early universe and gamma ray bursts. Finally, I will compare the models to observations and list future plans.
Unearthing Stellar Dawn: The Search for the Chemical Remains of the First Stars
By Dr Torgny Karlsson
17 Jan 2008
A theoretical model for the early chemical enrichment history of the Milky Way is constructed, aiming in particular at the contribution from primordial pair-instability supernovae (PISNe). We argue that the apparent absence of any chemical signature characteristic of PISNe in the atmospheres of metal-poor Galactic halo stars is due to an observational selection effect. Whereas most surveys traditionally focus on the most metal-poor stars, we predict that early PISN enrichment tends to `overshoot’, reaching enrichment levels of [Ca/H] ~ -2.5 that would be missed by current searches. Existing observational data are utilized to place constraints on the primordial initial mass function (IMF). We furthermore predict that merely a few second generation stars with a dominant (i.e., >90%) contribution from PISNe is expcted to be found below [Ca/H] = -2 in a sample of 10 000 Galactic halo stars. The corresponding fraction of stars formed from gas exclusively enriched by PISNe is roughly a factor of 4 smaller. With the advent of next generation telescopes and new, deeper surveys, we should be able to test these predictions.
Is the search for the origin of the highest energy cosmic rays over?
By Prof. Alan Watson
24th April 2008
This question can now be asked because of two results obtained using data recorded at the Pierre Auger Observatory. It has been established, at the 6-sigma level, that the flux of the highest energy cosmic rays is suppressed at energies beyond 5 x 1019 eV and that above this energy an anisotropy in the arrival directions of the particles is apparent. The arrival directions appear to be associated with sources within the GZK horizon (z ~ 0.018 or 75 Mpc). From these observations it seems probable that we have
observed the long-sought Greisen-Zatsepin-Kuzmin effect, demonstrating that ultra-high
energy cosmic rays are of extragalactic origin. It is also probable that these
particles are protons, thus offering the possibility of insights into features of
particle physics at centre-of-mass energies 30 times greater than will be reached at
the LHC. Preliminary conclusions from studies of detailed features of extensive air
showers suggest that extrapolations from Tevatron energies may not be what have been
anticipated hitherto. Much further work remains to be done.
The Semantics of the Wondrous
By Dr Matthew Graham
3rd June 2008
Since the dawn of time, mankind has been obsessed with the meaning and significance of dynamic events in the night
sky. The emerging generation of synoptic sky surveys continues this tradition but also brings new challenges. In
this talk, I will review the current infrastructure that supports this field and discuss semantic issues that need
to be resolved.
Automated Detection of Coronal Holes
By Larisza Krista, Trinity College Dublin
12 June 2008
The subject of this research is the automated detection of solar coronal holes. Coronal holes are regions in the solar atmosphere which contain open magnetic field lines (Altschuler et al. 1972), which allow highly charged particles to escape the Sun, and therefore are sources of fast-speed solar wind (Krieger et al. 1973). Coronal holes extend from the upper chromosphere to the outer corona and their temperature and density is considerably lower than the quiet areas surrounding them. As a result of their lower density and emission measure, they appear as dark areas at X-ray and extreme ultraviolet wavelengths (Reeves et al. 1970, Vaiana et al. 1976).
The aim of this research is to establish automatic coronal hole detection using images at a single wavelength and at the shortest running time possible for near real-time analysis. This method is based on intensity thresholding (e.g., Gallagher et al. 1998) and can be used with differrent intruments and wavelengths. For our research we used SOHO/EIT 19.5 nm and Hinode/XRT X-ray images.
To locate coronal holes on solar corona images we use advanced image processing techniques. Once the coronal holes are located we study their physical properties ? e.g. the area, cetroid of the area, magnetic flux and the temperature.
Furthermore we aim to identify individual holes by registering their location and the time of their occurrence to provide information on their position and time of re-appearance after each solar rotation. We plan to study individual holes on a large scale, which to our knowledge has not been done before.
Our work will also provide an application useful in space weather forecasting. By knowing the position of coronal holes we can relate them to solar wind properties at Earth and so a prediction can be made as to when the high-speed solar wind will reach the Earth.
The Colours of Satellite Galaxies in Groups and Clusters
By Dr Andreea Font
8th May 16:00
Current models of galaxy formation predict satellite galaxies in groups and
clusters that are redder than observed. We investigate the effect on the colours
of satellite galaxies produced by the ram pressure stripping of their hot
gaseous atmospheres as the satellites orbit within their parent halo. We
incorporate a model of the stripping process based on detailed hydrodynamic
simulations within the Durham semi-analytic model of galaxy formation. The
simulations show that the environment in groups and clusters is much less
aggressive than previously assumed. The main uncertainty in the model is
the treatment of gas expelled by supernovae. With reasonable
assumptions for the stripping of this material, we find that satellite
galaxies are able to retain a significant fraction of their hot gas for several
Gigayears, thereby replenishing their reservoirs of cold, star forming gas and
remaining blue for a relatively long period of time. A bimodal distribution of
galaxy colours, similar to that observed in SDSS data, is established and the
colours of the satellite galaxies are in good agreement with the data. In
addition, our model naturally accounts for the observed dependence of
satellite colours on environment, from small groups to high mass clusters.
Galaxies in the Clowes-Campusano Large Quasar Group
By Gerry Williger, University of Louisville
7 August 2008 at 13:00, Le111
Large Quasar Groups (LQGs) are large, filamentary, non-virialised
structures on the
order of 100-200 Mpc which are analagous to quasar superclusters.
They are identified via structure-finding algorithms and could be
useful as areas to study efficiently the relation between
quasars and galaxies, and the nature of galaxies in large variety
of environments, from low to high density regions. I will present
preliminary results from a multi-wavelength UV-optical study of
galaxy populations in two LQGs at z=0.8 and 1.2.
Element by Element Abundances from Integrated Light
By Prof. Guy Worthey
It will be a long time before individual, extragalactic main sequence
stars that are beyond the distance and crowding limits of the Hubble
Space Telescope can be studied. Integrated light studies of clusters
and galaxies are therefore of keen interest, since much of the same
information can be gleaned, such as age and abundance. This talk will
proceed through the translation of color-magnitude diagrams to the
Topics like the age metallicity degeneracy and the interdependence of
C, N, and O abundances will be touched upon, along the road to the
dream of a complete readout of chemical abundance pattern and age
structure of a distant stellar population based on its spectrum.
Scattered preliminary results of a new modeling effort are available.
A fairly large collection of elements are amenable to measurement in
high quality spectra, including more iron-peak elements and the
s-process tracer barium. The basic behavior with velocity dispersion
is that most elements (and age) have detectable dependences.
Magnesium, sodium and carbon have a strong increase with velocity
dispersion. Tentatively, nitrogen and barium behave a lot like iron
and nickel in that they have a very weak dependence on velocity
Positing three main sources of chemical enrichment, Type II supernovae
for light metals, intermediate-mass AGB stars for nitrogen and
s-process elements like barium, and Type Ia supernovae for heavy
metals, a fairly coherent concordance emerges if we assume that
chemical-enrichment timescales drive the observed variation with
velocity dispersion, and that more massive galaxies with higher
velocity dispersion quench star formation more quickly.
Stellar Population Models
By Dr. Claudia Maraston
Stellar Population Models are the classical tool to decipher
observational data and to derive the key physical properties of
galaxies and star clusters from the local up to the primordial
universe. Much progress has been made in this field over the last few
years. I shall review the current state of the models and discuss the
uncertainties and how these affect the interpretation of observational
data. I shall also present some very recent improvements and the
challenges for the future.
Stars and Massive Black Holes
By Dr Marc D. Freitag
May 23rd 15:00
Recently, observers have detected what is thought to be the result of
the direct interaction between stars and massive black holes: tidal
flares and hyper-velocity stars. In a decade or so, gravitational-wave
astronomy should allow us to witness the inspiral of compact stars
into massive black holes. Such observations call for a better
understanding of the stellar dynamics of galactic nuclei. I will
present the physical processes at play and review what numerical
models tell us about the structure and evolution of galactic nuclei.
Near-Field Cosmology, a theoretician’s point of view
By Dr. Alexander Knebe
The quantitative mastery of cosmology and galaxy formation is targeted
from two opposite directions: while observers use telescopes of ever
growing size to look back in time theoreticians model cosmic structure
formation and evolution from a period shortly after the big bang
forward in time until today. But only recently it became possible for
self-consistent cosmological simulations to make credible predictions
for galaxies and their properties that can be directly compared to
objects in the local Universe where observations are most complete and
In this talk I will introduce you into this exiting discipline
referred to as “Near-Field Cosmology” that gauges cosmology on small
scales. After a short primer on computational cosmology I am going to
present some of my recent research highlights regarding the dynamics
of satellite galaxies as derived from such simulations of cosmic
Local group dwarf galaxies in the Lambda-CDM paradigm
By Dr. Jorge Penarrubia
Dwarf spheroidal (dSph) galaxies may represent a keystone to test
predictions from the present cosmological paradigm: Cold Dark Matter
(CDM). Firstly, dSphs are the most dark matter-dominated galaxies in
the Universe known thus far and provide an ideal testbed to study the
elusive nature of dark matter. Secondly, dSphs are the faintest
galaxies in the Universe and as such, they play a key role in galaxy
formation models. In this talk I will discuss how dwarf galaxies in
the Local Group can be used to put strong constraints on galaxy
formation/evolution processes in the present cosmological
paradigm. Our methods go from analytical models that assume dynamical
equilibrium to high-resolution N-body simulations. I will show that
our results provide a remedy for the “missing satellite problem” and
prove the low efficiency of dark matter halos to form stars as the
galaxy mass decreases. In addition, N-body experiments that simulate
the evolution of dSphs in the host’s tidal field will be
presented. our results show that dSphs are extremely resilient to
tidal mass stripping: a dSph must lose practically all the dark matter
beyond the luminous radius (approx. 90–99% of the initial virial
mass) before starting to shed its stars. Our simulations also show
that tidal evolution occurs in a way that preserves the scaling
relations observed in the Local Group dSph population. Finally, I will
discuss the signatures of tidal mass stripping that can be observed
nowadays in some Milky Way dSphs.
A New Global Magnetic Field Model for the Solar Corona
By Dr. Duncan Mackay
The talk will describe a new global non-linear force free field model
for the solar corona. The model which is based on real observed data,
simulates the evolution of the photopsheric and coronal fields of the Sun
for long periods of time (weeks-months), whilst maintaining accurancy to the true observed photospheric fields. The model is applied to explain the
transport of magnetic helicity across the solar surface and the
hemispheric chirality pattern of filaments. It will be shown that the model can produce agreement with the observations of filaments in 96% of the cases,
where it is equally sucessful in explaining both the dominant and minority chirality patterns. Future applications of the model will be discussed.
The First Stars: Clues from QSO Absorption Lines
By Prof. Max Pettini
The epoch of re-ionisation, when the first stars heralded
the end of the cosmic dark ages and made the universe
accessible to optical and infrared telescopes, has
been described as the last frontier in current
observational cosmology. It is a topic which in the last
few years has been attracting the attention of several
different groups of astronomers, whose interests are
converging on this crucial phase in the evolution of the
universe. In my talk I shall describe recent work
which uses the absorption spectra of distant quasars
to uncover clues to the nature of the earliest episodes
of star formation and nucleosynthesis.
Nuclear Star Clusters: Formation and Relation to Black Holes
By Dr. Anil Seth
Nuclear star clusters are found at the centers of most lower mass
spiral and dwarf elliptical galaxies. They have similar sizes to
globular clusters, but are orders of magnitude more luminous and
massive. Recent studies have shown that nuclear star cluster masses
scale with galaxy or bulge mass in the same way as supermassive black
holes, and thus seem connected to the overall evolution of their host
galaxy. I will focus on initial results from a survey of the nearest
nuclear star clusters (D < 5 Mpc) in which the process of nuclear star
cluster assembly can be viewed in detail. Using a variety of data,
including adaptive-optics-corrected integral field unit spectroscopy,
we show that nuclear star clusters appear to form episodically from
material accreted onto the nucleus from the surrounding galaxy. This
data will also enable us to constrain the mass of any massive black
holes present in these low-mass galaxies. I will also discuss results
from a study of galaxies that have both nuclear star clusters and AGN.
Magnetospheric Substorms: Arguable Triggers, Aurorae and Unwanted Amperes
By Dr. Jim Wild, Space Plasma Environment and Radio Science Group, Department of Communication
Systems, Lancaster University.
Substorms are explosive reconfigurations of the magnetosphere resulting from the release of solar wind
energy and momentum stored in the Earth’s magnetic tail. Although the focus of study for over forty years,
the location and timing of the magnetospheric instability that initiates the onset of a substorm remains one
of the most significant outstanding questions in solar-terrestrial physics. Furthermore, some studies over
the last decade have suggested that the instability responsible for subtorm expansion phase onset may
require an external trigger (i.e. a triggering factor in the solar wind or interplanetary magnetic field,
rather than the magnetosphere). In this seminar, I shall summarise ongoing research at Lancaster into
possible substorm triggering, new experiments to investigate auroral dynamics and substorm onset timing, and
the relationship between substorms and geomagnetically induced currents in electricity distribution grids.
Observing with Herschel
By Dr. Bernhard Schulz
The Herschel Space Observatory is scheduled for a launch in April of
2009 together with the Planck mission and will give unprecedented
access for astronomers to the 55 – 670 micron wavelength range
(530-5000 GHz). Its 3.5 m mirror constitutes the so far largest
astronomical aperture in space. Herschel is an ESA cornerstone mission
built in an international collaboration with many of its European
member states, Canada and the US.
In the 55-200 micron range the PACS camera arrays with 3 filter bands
and its integral field spectrometer will achieve substantially higher
spatial and spectral resolution than previous missions like IRAS, ISO
or Spitzer. The so far almost completely unexplored wavelength range
between 200 and 670 micron will become accessible down to the
confusion limit to array photometry in 3 bands and FTS field
spectroscopy with the SPIRE instrument. The HIFI heterodyne
spectrometer with a single aperture will allow for the highest
spectral resolutions of 10^3 – 10^7 between 157 and 625 microns.
The mission will offer observing time to the entire astronomical
community that will be allocated to maximize the scientific output
achievable in the duration of the mission, limited by the amount of
cryogen it carries. Although a major fraction of the available
observing time has already been allocated to large Key Programmes and
their consortia, a call for open time small projects will be issued 6
months into the mission, soon after the completion of the performance
and science verification phases.
In my talk I will give an overview over the instruments, their
observing modes, and the common science data system through which the
observer performs observation planning, and science data processing.
The Relationship Between EUV Dimming and Coronal Mass Ejections
By Dr. Danielle Bewsher
There have been many studies of EUV dimming in association with coronal mass ejection (CME) onsets. However, there has never been a thorough statistical study
of this association, covering appropriate temperature ranges. We use a large campaign database from SOHO/CDS and SOHO/LASCO to associate dimming events
detected at 1 and 2 MK with CME activity. The results confirm the CME-EUV dimming association using statistical analysis for the first time. The results stress
that one emission line may not be sufficient for associating dimming regions with CMEs.
Designing Decentralized Control of Modular Robots
By Prof. Toshihiro Kawakatsu
We will discuss how to design modular robots by considering the interplay between the control and the
mechanical systems. A “modular robot” consists of multiple (sometimes many) modules which are
mutually communicating via data exchange and direct physical contact. These two ways of
communication can be identified with the neural system and the body dynamics system of living
bodies. We expect that the most optimal control system that the living bodies adopt is constructed on
a well-balance between the body mechanics and the neural system.
Solar Sources of Heliospheric Near-Relativistic Electrons:
Insights from Monte Carlo Simulations.
By Dr. Neus Agueda
Solar near-relativistic electrons (NR; > 30 keV) are observed as discrete
events in the inner heliosphere following different types of solar
transient activity. Determining the solar origin of a given NR electron
event is a difficult proposition because they are frequently associated
with both solar flares and coronal mass ejections (CMEs) whose onsets are
We use Monte Carlo simulations to model the transport of NR electrons
along the interplanetary magnetic field, with the goal of inferring the
underlying solar injection profile and the interplanetary transport
conditions based on particle observations at 1 AU. We apply this model in
order to carefully study a decade of events observed by the Advanced
Composition Explorer spacecraft.
We find that there is no single scenario operating in all of these events.
The interplanetary propagation of NR electrons can occur under both strong
scattering and almost scatter-free propagation conditions. Several
injection phases (related to flare and CMEs) are possible.
Colloidal rod suspensions: Why are they interesting and what can
we learn from them?
By Dr. Georgina M. H. Wilkins
Complex colloidal suspensions are found everywhere: from suspensions of
cells in blood plasma to suspensions of wax fibres in paints and sealants.
suspensions are used to modify the texture of cosmetics, improve the
and reduce the environmental impact of fuel via catalysis, modify the flow
properties of crude oil to assist in oil extraction and they are added to
detergents to maintain the stability of the soap molecules. Understanding
in which colloidal parameters including the rod aspect ratio (r =L/D),
and interaction potential control the microscopic and macroscopic
suspensions can lead to the development of new smart materials. We use
light scattering and microscopy to characterize polyamide rod suspensions.
results can be applied to develop strategies for complex fluid
stabilization, as well
as for fundamental studies of rod gelation and vitrification.
IMBHs in Star Clusters, Are They There?
Dr. Eva Noyola
I will give a brief summary of the most important dynamical processes
occuring in star clusters, as well as the reasons why we think we
should be looking for intermediate-mass black holes in them. I will
review relevant observational and theoretical results for this field
and I will present details about recent studies for omega Centauri and
M54. I will also discuss new results on photometric diagnostics for
the presence of IMBHs in globular clusters.
Cosmological Magnetic Fields: What do we Learn from Numerical Simulations?
Dr. Yohan Dubois
Using adaptive mesh refinement simulations we have described the
evolution of the magnetic field in the hot plasma of a galaxy
cluster. We pointed out that this field is more amplified in the
cluster core when the cluster experienced a cooling flow than in a
pure adiabatic case. Active Galactic Nuclei can produce high velocity
jets that modify the structure of those cluster cores. This
ultra-energetic feedback can enhance or shut down the amplification of
magnetic field. By performing high resolutions simulations we will try
to detail the impact of AGN on the evolution of coherent magnetic
fields. We will show that expanding galactic winds due to supernovae
feedback can describe a coherent scenario of the magnetic enrichment
of the inter-galactic medium, and then explain the origin of the
magnetic field at very large-scale.
Giant Impacts and Planetary Evolution
Dr. Craig B. Agnor
The planetesimal hypothesis posits that solid rocky and icy planets
form via the accumulation of smaller bodies. In this picture,
collisions between bodies is the mechanism by which planets acquire
mass and a principal process of planetary evolution. Giant collisions
between like-sized planets have been invoked to explain several bulk
planetary characteristics (e.g. the origin of Earth’s Moon and
Mercury’s large iron core).
In this talk, I will discuss how these giant impacts arise in the
context of planetary formation and our effort to explicitly model
these collisions. I will discuss the connections between the
different stages and regimes of planetary growth, the giant impact
outcomes expected, and the implications for the thermal, rotational
and compositional evolution of emerging planets.
What can soft X-ray sigmoids tell us about flux rope
Dr. Lucie Green
Soft X-ray images of the Sun have shown that some active regions
contain loops, or collections of loops, which appear forward or
reverse ‘S’ in shape. These structures are known as sigmoids and are
of interest because sigmoidal active regions have a high probability
of producing an eruption.
Different models have been put forward to explain the magnetic
topology of sigmoids. We investigate these models by studying
eruptions from sigmoidal regions. In several cases we find that the
observations support a flux rope topology being present during the
eruption phase, and that the sigmoid is formed at the interface
between the flux rope and surrounding arcade field. We use Hinode and
Yohkoh observations to investigate which sigmoid models are realistic
and when and how the flux rope formation occurs. We find evidence for
a transition from an arcade to a flux rope topology before eruption
onset, and that the flux rope has a bald patch separatrix surface
The diverse plasma interactions of Saturn’s icy moons
Dr. Geraint Jones
Since July 2004, the Cassini-Huygens spacecraft has been orbiting Saturn
and occasionally encountering the planet’s many moons. Most of these
satellites orbit within Saturn’s magnetosphere, and their interactions
with the planet’s magnetospheric plasma has been studied by the
spacecraft’s particles and fields instruments. Much attention has been
given to this interaction at the largest moon, Titan, which possesses a
thick, chemically-complex atmosphere. Other icy satellites, however,
also have a surprisingly complex interaction with the plasma. Most
striking is that at the active moon Enceladus, which feeds the
magnetosphere with neutral gas and icy grains expelled from surface
fractures. The ionized component of this material and its byproducts
affects the dynamics of the magnetosphere as a whole, and the plasma
instruments are providing a wealth of information on the nature of the
material originating at this mooon. Rhea’s interaction with energetic
electrons revealed the presence of a debris disk and possible rings
orbiting the moon itself. The interactions at other moons, including
Dione, Tethys, Iapetus, and smaller moons only recently discovered by
Cassini are also reviewed, demonstrating how we can use in situ plasma
measurements to complement knowledge of the moons’ surfaces and
interiors as learned from remote sensing imagers and spectrometers.