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| Date | Speaker | Topic |
|---|
| 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) |
A Planetesimal Pas de Deux or the Clash of the Titans: A Model for Collisions in Planet Formation |
| Collisions are the core component of planet formation. The range of impact parameters encountered during growth from planetesimals to planets span multiple collision outcome regimes: cratering, merging, disruption, and hit-and-run events. Because of the range of collision outcome and variations in the material properties of planetary bodies, no general set of equations exist to capture the basic physics of collisions. At present, collision outcomes in planet formation simulations are applicable only to a specific subset of possible collision parameters. Using new high-resolution simulations of collisions between planetesimals for a wide range of impact parameters we have derived a complete analytic description of the dynamical outcome for any collision between gravity-dominated bodies (100 m planetesimals to planets). We then apply our new model to published results of the stochastic end stage of planet formation. We find that our predicted timescale of planet formation is significantly increased, mass and volatile content of the planets is reduced, and the diversity of resulting planets is significantly changed by our collision outcome model. It is clear from this work that more realistic modelling of planetesimal evolution is required if we are to understand the prolific production of planets in detail. |
| May 8 |
Alberto Vecchio
(Birmingham) |
Studying populations of black holes and neutron stars with gravitational wave observations |
| Compact binary systems containing neutron stars and/or black holes are one of the most promising sources for ground-based gravitational-wave laser interferometers, such as Advanced LIGO and Virgo that are expected to begin science data taking in 2015. Gravitational waves encode rich information about source physics. I will discuss the prospects for precise measurements of the source parameters - such as masses and spins - that describe the underlying physics, and for studies of populations of compact objects enabled by this new observational window.
|
May 13
MONDAY, 1PM |
David Neufeld
(John Hopkins University) |
Probing Molecular
Clouds with Observations of Interstellar Hydrides: recent results from
Herschel and SOFIA
|
| Interstellar hydrides - that is, molecules or molecular ions containing a single heavy element with one or more hydrogen atoms - have proven to be invaluable probes of molecular interstellar material, both in the Milky Way and in distant galaxies. Seven neutral diatomic hydrides have now been observed in the interstellar gas - CH, NH, OH, HF, SiH, SH, and HCl - along with four diatomic hydride cations (CH+, OH+ , SH and HCl+) and several polyatomic species (e.g. CH2, NH2, H2O, H2O+, H2S, H2Cl+, NH3, H3O+). Because the hydrides possess small momenta of inertia relative to molecules that contain two or more heavy atoms, their rotational transitions lie at high frequencies that are often inaccessible from ground-based observatories (at least at z=0, i.e. in the local Universe). Thus, the observational study of interstellar hydrides has benefitted greatly from new capabilities offered by the Herschel Space Observatory and the Stratospheric Observatory for Infrared Astronomy (SOFIA). Because the chemical pathways leading to the formation of interstellar hydrides are fairly simple, the analysis of the observed abundances is relatively straightforward, and provides key information about the physical and chemical conditions within the environments in which hydrides are found. In this presentation, I will review how quantitative measurements of the abundances of hydride molecules have provided important information about several key parameters in the diffuse ISM: the cosmic ray ionization rate, the H2/H ratio, the UV radiation field and the rate of dissipation of interstellar turbulence. Future observations with ALMA promise to extend the diagnostic power of hydride molecules to the high-redshift Universe.
|
| 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 |
