| January 7, 2008 | |
|
|
AAS Meeting
|
| January 14, 2008 | |
| Bryant 217 | George Lake (University of Zurich) |
|
|
Some Open Problems with Lambda CDM |
| Abstract | I'll review a few of the puzzles that remain in our standard model. These include: forming disks, finding dark matter substructure,galaxy luminosity functions and reconciling predicted central dark matter density cusps with observations. |
| January 21, 2008 | |
|
|
Martin Luther King Jr. Day
|
| January 28, 2008 | |
| Bryant 217 | Jonathan Langton (UCSC) |
|
|
Atmospheric Dynamics on
Unevenly Irradiated Jovian Planets |
| Abstract | The increasingly rapid pace of the discovery of extrasolar
planets has brought to light a number of worlds with properties vastly
different from those in out own solar system. Dramatic examples
of this variety are provided by a class of planets with highly
eccentric (e> 0.3) orbits, with very close (a(1-e) < 0.05 A.U.)
periastron passages. On these planets, the subsolar irradance
varies by a factor of 3 to 1000, typically reaching ~10^6 W/m^2 at
periastron. I will present the results of two-dimensional hydrodynamic simulations of the upper atmospheres of these planets. The flow geometry is complex, turbulent, and primarily driven by the sudden influx of energy at periastron. I will focus attention on 4 particularly interesting planets. HD 80606 b (e= 0.9321) has the largest eccentricity of any planet yet discovered. HAT-P-2 b (e=0.507) presents a particularly promising observational target due to the large infrared flux variation we predict, and due to the fact that it transits its parent star. HD 17156 b (e= 0.67) also transits. Finally, HD 37605 b (e=0.737), while not particularly suitable for observation, occupies an especially interesting dynamical regime, with persistent circumpolar vortices shielding their interiors from most of the periastron heating. |
| February 4, 2008 | |
| Bryant 217 | Sven van Loo (Leeds University) |
|
|
The effect of ion-neutral drift on the formation of dense cores in GMCs |
| Abstract | Molecular clouds are highly structured. It is often asserted that highly turbulent gas produces the high-density inhomogeneities.Turbulent gas can be generated by different mechanism as there are shock waves of supernovae, individual stellar winds or wind-blown bubbles around OB stars and outflows from newly formed low-mass stars. As the molecular clouds are threaded by magnetic fields, the turbulence can be interpreted as a summation of magnetosonic waves. Analytic analyses and numerical simulations following the evolution of a single wave show that the generation of large density perturbations is associated with slow-mode waves and that this process works on different length-scales. In these simulations the medium was treated as a single ideal plasma in which the gas is perfectly coupled with the magnetic field. However, the low ionisation fraction within molecular clouds implies that the gas and the magnetic field are actually weakly coupled and, thus, ambipolar resistivity becomes important. Using multifluid adaptive mesh magnetohydrodynamic simulations, we examine the effect of ambipolar resistivity on the generation of density perturbations. Our results show that it affects waves with wavelengths up to two orders of magnitude larger than the dissipation length scale, effectively inhibiting the generation of dense structures below 0.01 pc. |
| February 11, 2008 | |
| Physics 2165 | Dimitri Veras (UF Astronomy) |
|
|
Dynamics of Extrasolar
Planets on Detectably Wide or Deceptively Circular Orbits |
| Abstract | I will discuss two new distinct projects: 1) Prospects
for directly imaging extrasolar planets hundreds or thousands of AU
away from their parent stars are improving. I will show how
planets can remain stable in these "extreme" orbits, and link the
viability of planetary formation mechanisms with the success rates of
future imaging surveys. 2) Commonly-used orbit
determination methods may mask important dynamical features of
exoplanetary systems. By combining radial velocity observations
of the HD 12661 multi-planet system with n-body integrations, I
demonstrate that the currently-observed nearly-circular orbit of the
system's outer planet is atypical and hides the more dynamically active
nature of the system. |
| February 18, 2008 | |
| tba | Jonathan Tan
(UF Astronomy) |
|
|
Primordial Star Formation |
| Abstract | I review our current understanding of how the first,
metal-free stars formed in the high redshift universe. I discuss how their initial masses are expected to be set by a combination of accretion physics and radiative feedback processes. I describe similarities and differences of primordial star formation to present-day star formation, including possible effects of dark matter annihilation and magnetic fields. |
| February 25, 2008 | |
| Bryant 217 |
Jay Onifer (UF
Physics) |
|
|
Mass Loss From Evolved Massive
Stars |
| Abstract | Wolf-Rayet (WR) stars are massive stars on the last
stable stage before supernova and are thought to be the progenitors of
long-duration gamma-ray bursts. They are also dominant
contributors of stellar-enriched material to the interstellar medium,
owing to their dense, fast winds with large mass-loss rates. Since their winds are optically thick, understanding stellar properties requires modeling the complex wind behavior. I will give an overview of theoretical models for WR winds, focusing primarily on analytic methods. |
| March 3, 2008 | |
|
|
|
| March 10, 2008 | |
|
|
Spring Break
|
| March 17, 2008 | |
| Bryant 217 |
Anthony Gonzalez (UF
Astronomy) |
|
|
The Distribution of Baryons
in Galaxy Clusters and Groups |
| Abstract | If galaxy clusters are indeed fair samples of the universe,
then a basic expectation is that the baryon fraction in clusters and groups should reflect the universal value. Observed shortfalls have therefore led to proposals of missing baryons in a warm gas component, as well as other more controversial interpretations. I will present the results of a program to understand the distribution of baryons in nearby galaxy clusters and groups, as well as the properties of their central galaxies. A main focus of this work is to quantify the total stellar baryon fraction, including stars in both galaxies and the intracluster light, and combine these data with published measurements of the hot baryon fraction in the intracluster medium (ICM). We find that the total baryon fraction is independent of cluster mass, with no compelling evidence for missing baryons. I will also present related results from this program pertaining to cluster galaxy evolution, galaxy structure, and chemical enrichment of the ICM. |
| March 24, 2008 | |
|
|
|
| March 31, 2008 | |
| Bryan 217 |
Qualifying
Exam: Miguel Charcos |
|
|
1 pm |
| April 7, 2008 | |
| Bryant 217 |
Heather Ray (UF Physics) |
|
|
Core Collapse Supernovae :
Neutrino emission and terrestrial detection |
| Abstract | Theoretical models of core-collapse supernovae have up to a
50% uncertainty in their predictions of the mechanisms which cause the explosion. A star undergoing core-collapse supernova emits a pulse of neutrinos that can be observed using a terrestrial based neutrino detector. Supernova model uncertainties can be reduced through direct detection and study of this emitted neutrino pulse, or by performing relevant neutrino-nucleon cross section measurements at an Earth-based facility. This talk will describe the properties of neutrinos emitted during core-collapse supernova, what we can learn by studying them, and how to implement a supernova search at the MiniBooNE neutrino detector. I'll briefly describe a neutrino experiment proposal at Oak Ridge, TN, whose goal is to measure neutrino-nucleon cross sections relevant for supernova predictions. |
| April 14, 2008 | |
| Bryant 217 |
***
Valerie Mikles
Disseratation Talk *** |
|
|
1:30 pm |
