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| Date | Speaker | Topic |
|---|
| January 16 |
Ettore Carretti
(CSIRO) |
S-PASS and the Giant Magnetised Outflows from the Centre of the Milky Way
|
| The S-band Polarization All Sky Survey (S-PASS) has mapped the polarized radio emission of the entire southern sky at 2.3 GHz with the Parkes Radio Telescope. Aimed at overcoming the depolarization issues of previous surveys taken at lower frequencies (1.4 GHz), S-PASS has unveiled the diffuse polarized emission down to the Galactic disc revealing new and surprising large scale structures. The scientific results that are being obtained are diverse and cover opposite ends of the astrophysics research. In this talk I'll focus on two huge lobes, giant magnetised outflows we have discovered to come out from the Centre of the Milky Way and that are the radio polarized counterpart of the Fermi Bubbles. Extended for some 120 deg in sky, our analysis tells these are star-formation driven outflows bringing a massive magnetic energy of a few 10^55 erg and a strong magnetic field from the compact star formation area orbiting the Galactic Centre out into the Galactic Halo. We also find three ridges on the outflow surface that, we suggest, are record of the star formation activity of the Galactic Centre area of the last ~10 Myr. |
| January 30 |
Jeronimo Bernard-Salas
(IAS) |
Circumstellar and Interstellar Fullerenes |
| Fullerenes are large molecules made of carbon arranged in a spherical or ellipsoidal configuration. These molecules were discovered in laboratory experiments aimed at understanding the formation of long carbon chains in the circumstellar environment of carbon stars. Recently, we reported the first detection of fullerenes (C60, C70) in space, specifically in Tc1, a young planetary nebulae (PNe). Once injected into the ISM these stable species survive, and are thus probably widespread in the Galaxy where they could contribute to the interstellar extinction, heating processes, and complex chemical reactions. Following our discovery, fullerenes have now been detected in a wide range of sources (post-AGBs, PNe, reflection nebula, HII regions, H-poor stars, and YSOs), showing that when conditions are favorable, fullerenes are formed in large quantities. These findings suggest that the circumstellar envelope of evolve stars could be the birthplace of fullerenes. However, their excitation mechanisms - which sets diagnostic value - and formation routes are not yet understood. In this talk I will review our current knowledge on fullerene detection, and I will discuss the pros and cons of the various proposed excitation and formation mechanisms. |
| February 6 |
Rubina Kotak
(Queen's Belfast) |
Supernovae arising from massive stars: current enigmas and future prospects |
| One of the main challenges of current supernova research is to identify
the nature of stars that explode, and link this knowledge to the
observed supernova properties. Nowhere is this problem more urgent than
for the most massive stars in the local and distant Universe. Recent exciting
results have challenged currently accepted paradigms of stellar evolution, and
for these supernovae, ever more exotic scenarios are being proposed.
I will discuss these within the framework of what is currently known about
the progenitors of core-collapse supernovae. Massive star supernovae have an
enormous impact on their surroundings; I will focus on one particular aspect
that this may take, namely, enriching the intergalactic medium with metals
and dust at epochs when the Universe was only a small fraction of its current
age. I will end by speculating on how such studies might evolve in the light of
current and future surveys / facilities.
|
| February 13 |
Alexei Smirnov
(ICPT Trieste) |
Schuster Colloquium - Neutrinos: Flavours of the Invisible |
| Abstract to come |
| Abstract to come |
| February 27 |
Matt Auger
(Cambridge) |
How is dark matter distributed on sub-Mpc scales? |
| Cold dark matter provides an excellent description for the structure of the universe on scales of 10s to 100s of Mpc. However -- in spite of its fundamental importance -- the distribution of dark matter on smaller scales, e.g., in the centres of galaxies and clusters, largely remains unknown. Our ignorance is in part due to the difficulty of making mass measurements on these scales, but also results from degeneracies between the dark matter structure and the mass-to-light ratio of baryons. I will describe how strong gravitational lensing measurements can be used in concert with other mass probes -- including dynamical, weak lensing, and richness-based masses -- to break the stellar/dark mass degeneracy and provide robust constraints on the central dark matter structure of galaxies and poor clusters. Surprisingly, the inferred stellar mass-to-light ratio of massive bulges is significantly larger than in galaxy disks, implying a variation in the IMF from hot spheroidal systems to cold disks. Additionally, galaxy-scale halos may have an excess of central dark matter compared to dark-matter only simulations, while, in contrast with previous studies, cluster halos are consistent with scaling relations from dark matter simulations. |
| March 6 |
Robert Crittenden
(Portsmouth) |
The Intrinsic Non-Gaussianity of the Microwave Background |
| Abstract to come |
| March 13 |
Sarah Bridle
(Manchester) |
Schuster Colloquium - Seeing the Invisible: Observing the Dark Side of the Universe |
| It seems that most of the universe is made up of mysterious ingredients which we cannot see directly. I will describe "gravitational lensing", the bending of light by gravity, which is predicted by Einstein's General Relativity. The dark components of the universe do not emit or absorb light, but do exert a gravitational attraction, and it turns out that gravitational lensing is one of the most promising methods for finding out more about them. This is very similar to looking through a bathroom window at street lamps outside, and using the distorted images to learn about the patterns in the glass. I will describe the recently started Dark Energy Survey which will observe shapes and approximate distances to 300 million galaxies over one eighth of the entire sky. |
| March 20 |
John Brown
(Glasgow) |
Supersonic Snowballs in Hell - The Physics of Sun-Plunging Comets |
| Bombardment of young planets by large 'minor' bodies (rocky asteroids and dusty snowball comets)
played a major role in the early solar system and has been invoked as the source of
earth's water and of some species extinctions. Planetary impacts continue to this day
with at least 3 easily visible Jupiter impacts having occurred since 1994 and a sizeable
impact in Siberia (Tunguska) in 1910. Besides the threat they pose, these objects are of interest in being composed of primordial solar system matter.
The first space observation of a smallish comet falling irreversibly 'into' the sun was made by spaceborne white light coronagraph ~ 1980. Though first thought to be very rare, these 'sun-grazing' comet destructions are now known to occur almost daily. Surprisingly the theory even of the physical regimes of destruction of these giant (10-1000 metre) supersonic (600 km/sec) snowballs in the Hellish near-sun regime has only very recently been published (Brown et al. 2011, A&A 535, A71) and the first actual destruction in the inner solar atmosphere (as opposed to non-re-emergence in coronagraphs of r>> Rsun) was only made (in the UV) in July 2011 by the Solar Dynamics Observatory SDO launched in 2010 (Schrijver, Brown et al 2012 Science 335,324). In December 2011 SDO and other observatories saw the largish sungrazer Comet Lovejoy just survive its skim over the sun at less than 1.2 solar radii
I will summarise the background to, main features of, and future directions in this emerging new branch of comet and solar science involving the interaction of a supersonic cold solid state body with a hot hydrogen plasma 10^8-10^16 times less dense. The dominant process of mass loss of the icy nucleus will be shown to be sublimation by solar radiation , ablation by solar atmospheric bombardment. or explosion by atmospheric ram pressure, depending on the nucleus mass and perihelion distance. The first (SDO event) regime involves a relatively gentle 'fizzle' over minutes to hours while the latter two (yet to be seen directly) are impulsively explosive (< 10 sec) and should produce phenomena somewhat like magnetic solar flares,including multi-wavelength bursts and 'sunquake' waves in the photosphere though with highly non-solar element abundances and spectral signatures. Because of the rapid exponential increase of solar density with depth, even the most massive comets ever mooted (~1e19 kg ~ 1000 Hale-Bopps)are destroyed well above the photosphere where the collisional heating is 100,000 times sunlight. The superflare caused by such a body would have major terrestrial and human consequences |
| March 27 |
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Easter |
| April 3 |
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Easter |
| April 10 |
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Easter |
| April 17 |
David Kirkby
(Irvine, California) |
How to measure the universe with cosmic sound |
| I will describe the first observations of baryon acoustic oscillations (BAO) in the clustering of the inter-galactic medium. The analysis uses a large sample of high redshift (z ~ 2.4) quasars observed by the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS) to probe the Lyman-alpha forest. We estimate the 3D correlation function of the transmitted flux fraction and simultaneously measure the BAO comoving standard ruler along and transverse to the line of sight using some novel fitting techniques. We interpret these measurements as constraints on the recent expansion history of the universe and the role of dark energy. |
| April 24 |
Ken Anderson
(ESS, Sweden) |
Schuster Colloquium - The European Spallation Source: Opportunities for Science and Technology |
| Abstract to come |
| May 1 |
Zoe Leinhardt
(Bristol) |
TBC |
| Abstract to come |
| May 8 |
Alberto Vecchio
(Birmingham) |
TBC |
| Abstract to come |
| May 15 |
Phil Diamond
(SKA Project Office) |
TBC |
| Abstract to come |
| May 22 |
Omar Almaini
(Nottingham) |
The interaction between distant galaxies and their environments |
| I will discuss the strong connection between galaxies and their environments in the high-redshift universe (z>1), as revealed by recent deep surveys. On large scales, studies of galaxy clustering have shown that passive galaxies inhabit the most massive dark matter halos from z=2 to the present day. The precise mechanism responsible for terminating star formation remains unclear, but clustering studies reveal that massive galaxies may shut off their star formation once their host halos achieve a critical mass. On smaller scales, recent deep spectroscopic surveys have allowed the first studies of galactic outflows and the processing of metals in typical high-redshift galaxies. Large-scale outflows appear to be ubiquitous for star-forming galaxies at z>1, with outflow rates comparable to the rates of star formation. There is also evidence for a strong link between outflows, inflows and the evolution in the mass-metallicity relation. The key physical processes are not fully understood, but a picture is gradually emerging of the complex interplay between distant galaxies and their environments. |
| May 29 |
Andrew Jaffe
(Imperial) |
TBC |
| Abstract to come |
| June 5 |
Rob Fender
(Southampton) |
Radio Transients |
| Abstract to come |
