Events for December, 2009

Friday, 04 December 2009 12:00 pm [see hoagie list] Princeton University ~ Gravity Group Astrophysics/Cosmology Lunch Jadwin 102 (Joe Henry Room) Speaker:   Daniel Grin (Caltech) Topic:   Cosmological hydrogen recombination: the effect of high-n states and forbidden transitions. Abstract:   Thanks to the ongoing Planck mission, a new window will be opened on the properties of the primordial density field, the cosmological parameters, and the physics of reionization. Much of Plancks new leverage on these quantities will come from temperature measurements at small angular scales and from polarization measurements. These both depend on the details of cosmological hydrogen recombination; use of the CMB as a probe of energies greater than 1016 GeV compels us to get the ~eV scale atomic physics right. One question that remains is how high in hydrogen principle quantum number we have to go to make sufficiently accurate predictions for Planck. Using sparse matrix methods to beat computational difficulties, I have modeled the influence of very high (up to and including n=200) excitation states of atomic hydrogen on the recombination history of the primordial plasma, resolving all angular momentum sub-states separately and including, for the first time, the effect of hydrogen quadrupole transitions. I will review the basic physics, explain the resulting plasma properties, discuss recombination histories, and close by discussing the effects on CMB observables.   3:00 pm Princeton University ~ Gravity Group Special Seminar Jadwin 102 (Joe Henry Room) Speaker:   Valeria Pettorino (Columbia University) Topic:   LOCATION: PCTS seminar room!!! Title: Coupled quintessence and impact on structure formation Abstract:   I will describe the possibility that dark energy might interact with other species in the universe (cdm, neutrinos or within scalar-tensor theories). I will illustrate the impact of the coupling on observations, both at the linear and non-linear level. In particular, I will focus on growing neutrino quintessence, in which neutrinos can cluster at large scales, under the effect of a fifth force mediated by the dark energy scalar field.   Friday, 11 December 2009 12:00 pm [see hoagie list] Princeton University ~ Gravity Group Astrophysics/Cosmology Lunch Jadwin 102 (Joe Henry Room) Speaker:   Phil Korngut (University of Pennsylvania) Topic:   Astrophysics of the Intra-Cluster Medium in RXJ1347-1145 from High Resolution SZE Observations. Abstract:   Galaxy clusters are the most massive virialized objects in the universe and, as such, are extensively used as cosmological probes. The clusters are usually assumed to be relaxed, spherical, and isothermal to simplify the analyses. I will present new observations of the Sunyaev Zel’dovich Effect (SZE) in RXJ1347-1145 made at 90GHz (3.3mm) with the MUSTANG receiver on the 100m Green Bank Telescope (GBT). These data have an angular resolution of 10 seconds of arc, making the resulting image the most resolved map of the SZE made to date. This cutting edge new dataset has confirmed a previously reported strong, localized enhancement of the SZE 20” to the South-East of the center of X-ray emission. This enhancement of the SZE has been interpreted as hot (> 20 keV) gas caused by a recent, violent merger event and is one of only three confirmed shocks yet detected in the intra-cluster medium of galaxy clusters. I will also discuss recent improvements to the MUSTANG+GBT system and plans for future work on high resolution SZE measurements.