Date: Wednesday 03-Aug-2005
Speaker: Dr. Jave Kane, Lawrence Livermore National Laboratory
Title: Structure of Molecular Clouds - Observations and Modeling
Date: Tuesday 13-Sep-2005
Speaker: Dr. Rob Swaters, University of Maryland
Title: The Dark Side of Matter in Disk Galaxies
Date: Tuesday 27-Sep-2005
Speaker: Dr. Andrew Youdin, Princeton University
Title: Gravitational Collapse of Solids in a Turbulent Gas Disk: Not Your Father's Planetesimals
The formation of planetesimals, solids greater than a kilometer, will be addressed. Purely collisional growth of planetesimals from mm-sized grains faces several fundamental obstacles. As an appealing alternative, collective instabilities driven by self-gravity might gather small solids into planetesimals. Stirring by turbulence is thought to prevent such gravitational instabilities (GI). We show that when dissipation by gas drag is taken into account, GI persists even in the presence of moderately strong turbulence. Dissipative GI produces growth times and wavelengths longer than traditional dynamical collapse. Applications to the asteroid belt and mm-wave observations will be discussed.
Date: Tuesday 04-Oct-2005
Speaker: Dr. Ben Zuckerman, UCLA
Title: High-Resolution Infrared Imaging of Extrasolar Planets
Date: Tuesday 11-Oct-2005
Speaker: Dr. Bengt-Goran Andersson, Johns Hopkins University
Title: Dust Grains and Magnetic Fields: Considerations in Making Optical Polarimetry Quantitative
Date: Tuesday 25-Oct-2005
Speaker: Dr. Duilia de Mello, NASA Goddard
Title: Census of the star-forming galaxy population at intermediate redshifts
A key question in galaxy evolution is the physical nature of the intermediate redshift galaxies and their present-day counterparts. It is known that the star formation rate density increases rapidly from z=0 to z=1-2. However, the type of galaxies that contribute to the rise of the star formation density is still debatable. In principle, a steep luminosity function where most of the star formation is in newly-formed dwarf galaxies or a population of massive galaxies undergoing modest but continuous star formation can produce similar star formation rate density at a given redshift. Therefore, a census of the star-forming galaxy population as a function of time is needed in order to help us better understand how galaxies acquired their present morphology. In this talk, I will discuss the physical properties of a sample of UV-bright galaxies at intermediate redshifts which was compiled using GOODS/ACS data and the deepest U-band images ever obtained with HST using WFPC2 as part of the parallel observations of the UDF. I will conclude by showing that galaxies of all types, sizes and shapes are forming stars at intermediate z.
Date: Tuesday 08-Nov-2005
Speaker: Dr. Dieter Lutz, MPE Garching
Title: High-redshift infrared galaxies: Spitzer and millimeter views
Date: Tuesday 22-Nov-2005
Speaker: Kalliopi Dasyra, MPE Garching
Title: The evolution of local ULIRGs and their relation to QSOs from NIR spectroscopy
We are conducting an ESO VLT Large Program to study the dynamical evolution of local Ultraluminous Infrared Galaxies (ULIRGs). We have obtained near-IR ISAAC spectra of 54 ULIRGs at various merger timescales and derived their kinematics by measuring the stellar dispersion and rotational velocity along the slits. The kinematics of the (early-phase) binary ULIRGs indicate that ultraluminous luminosities are usually (but not necessarily) generated by mergers of almost equal-mass galaxies. By comparing the binary- to the single-system kinematics, dynamical heating of the merging hosts is observed, as the stellar dispersion increases with time. Placing ULIRGs on the fundamental plane of early-type galaxies shows that they form intermediate mass ellipticals. The black hole masses of the merged sources, calculated from their relation to the host dispersions, are of the order 10^7-10^8 M_sun. To investigate whether ULIRGs go through a QSO phase during their late-stage evolution, we have acquired ISAAC data for 12 local Palomar-Green QSOs. The dispersions of the IR bright QSOs of our sample are similar to those of ULIRGs, impying comparable black hole and host masses. Their Eddington efficiencies are high and their stellar populations indicate that they have undergone recent starbursts (Canalizo & Stockton 2001). Unlike the IR-bright, the (few) optically selected sources have a larger scatter in their kinematical properties; for these we will expand our work to obtain further spectroscopic data in the future.
Date: Tuesday 06-Dec-2005
Speaker: Tom Troland, University of Kentucky
Title: Massive Star Formation in the Galaxy: The Anatomies of Two Magnetized Star-Forming Regions
The Orion region (500 pc) is the nearest and best studied locale of massive star formation. The NGC 6334 region (1700 pc) has also been well studied. However, VLA studies of these two regions reveal new details of their structures, including the roles of magnetic fields within them. For example, magnetic fields may dominate the energetics of the thin veil of neutral material lying directly in front of the Orion Nebula. If so, the Orion veil is the only magnetically dominated region known in the ISM. Magnetic fields also play an important, although not dominant role in the molecular cloud NGC 6334A. And the anatomy of this H+ region/molecular cloud is apparently quite different from that previously assumed.
