Title & Abstract
Apr 18, 2008: Dr. Aaron Dutton (UC Santa Cruz)
“The Structure of Disk Galaxies: A Challenge to CDM?”
The Cold Dark Matter (CDM) framework successfully explains the origin of large scale structure in the Universe. However, on the scale of individual galaxies there are apparent contradictions between predictions of CDM and observations: these include the central density and angular momentum problems. I will address the question: Are these fundamental problems for CDM, or are they simply a reflection of observational biases and our incomplete knowledge of the physics of galaxy formation?
Apr 11, 2008: Ms. Ashley Ruiter (New Mexico State Univ.)
“Formation channels of Type Ia Supernovae and their associated delay times”
I will show expected SN Ia delay times for our population synthesis model calculations for various SN Ia formation channels, and discuss these results in context of recent observationally-derived delay times of SN Ia. Further, I will comment on how the variation of model parameters (common envelope evolution, star formation history, metallicity) affect the resulting delay times, in order to constrain possible SN Ia evolutionary
history scenarios.
Apr 11, 2008: Mr. Glenn Kacprzak (New Mexico State Univ.)
“Extended Halo Gas and Galaxy Kinematics in The Lambda-CDM Paradigm”
We present new results on the kinematics connections between the galaxy rotational velocities and associated halo gas velocities as measured in absorption. We also analyze mock quasar absorption line observations of galaxies and their gaseous halos in L-CDM cosmological simulations in order constrain the dynamic interaction of the galaxy/halo/cosmic web environment and the distribution of gas within halos. Previous observational results from six edge-on galaxies suggest that halo gas velocities are consistent with extended disk-like rotation. We demonstrate that the gas velocities are by and large not consistent with being kinematically coupled to the galaxy over galactocentric distances of 25-110 kpc. Mock absorption line analysis of simulated galaxies are consistent with our new observations. Together, the suggested picture in which gaseous halos are chemically enriched by outflowing shock-heated supernovae winds while low metallicity gas inflowing along filaments produces an inhomogeneous temperature, velocity, and metallicity distributions with a non-unity gas covering fraction.
Apr 4, 2008: Prof. Evan Scannapieco (Arizona State Univ.)
“AGN Feedback in Galaxies and Galaxy Clusters ”
For the past 10 billion years, the typical mass of star-forming galaxies has been decreasing, seemingly in direct conflict with the prevailing model of cosmological structure formation. On even larger scales, the gas in the centers of many galaxy clusters is observed to be rapidly cooling , yet this never leads to star formation on the central cD galaxy. Using smoothed particle and adaptive mesh hydrodynamic simulations, I will demonstrate that the solution to these mysteries is likely to lie in the formation of active galactic nucleii (AGN), which are capable of exerting strong feedback on their environments. A wide range of observations are fast uncovering the details of the key role these objects have played though cosmic time.
Mar 28, 2008: Prof. Mitch Begelman (Univ. of Colorado)
“The First Supermassive Black Holes?”
The existence of a supermassive black hole in nearly every galactic nucleus is no longer in doubt, but the question of how these black holes formed is wide open. I will argue that they could have formed directly via the infall and collapse of gas, without the intermediate stage of star formation, if the infall rate was high enough. Black hole formation by very rapid infall could have occurred in pregalactic haloes as early as redshifts ~10-20, or at lower redshifts in the nuclei of protogalaxies. Global gravitational instabilities get rid of excess angular momentum, and the infalling gas forms a self-gravitating, optically thick structure - a "quasistar". As matter piles on, the core of the quasistar heats up until it undergoes runaway neutrino cooling and collapses to form a 10 solar mass black hole. The black hole then grows by accreting from the quasistar at an extremely super-Eddington rate, possibly reaching thousands of solar masses in less than a million years. Concurrently, the quasistar expands to form a radiation pressure-dominated, convective envelope reminiscent of a red giant. I will discuss the structure and evolution of quasistars and their detectability with the James Webb Space Telescope.
Mar 7, 2008: Prof. Jerry Ostriker (Princeton Univ.)
“Black Hole Accretion and Radiative Feedback”
Black holes resident in the centers of galaxies will be fed by accretion of ambient gas
whenever gas reaches those central regions. This can be due to mergers, but even without mergers the evolution of the stellar populations of normal galaxies provides very large amounts of gas, as stars pass through the planetary nebula stage, with the total mass release being greater than 1011 Msolar for normal massive ellipticals. Much of that gas will cool and fall to the centers of the systems, where it will induce starbursts and
accretion events onto the central black holes. We follow these events with a high
resolution hydrodynamic code, allowing for radiative transfer, supernovae and other
relevant physical processes. In addition, we know the spectral output of accreting black
holes and we find that the high energy output from these objects will strongly inhibit
inflow, causing episodic accretion and a low “duty cycle”. The simulations help us to
understand many phenomena including the black hole stellar mass relation, the paucity of gas in ellipticals, the incidence of the “K+A” phenomena and the observed fact that most of the black holes found in galactic centers are in the “off” state.
Feb 8, 2008: Prof. Isaac Schlosman (Univ. of Kentucky)
“Disk Evolution in Assembling Dark Matter Halos”
Disk galaxy formation is a complex problem. In my talk, I will discuss
some aspects of disk formation and its subsequent evolution. Specifically,
I will include the disk-halo interaction and its dynamical feedback both on
the halo and on the disk, the dominant morphology of the early galactic
disks and the dark matter density profile in the galaxy.
Jan 14, 200: Dr. Tom Jarrett (Caltech/IPAC/JPL/Spitzer)
“The Hidden Realm of Deeply Embedded Supernovae Remnants”
During its relatively short lifetime, a supernova dramatically alters the birth cloud in which it arises, compressing, heating, ionizing and metal enriching the interstellar medium. In this regard, the most important class of supernovae (SNe) are those of the core collapse unique to the most massive stars. And yet these SNe are the least understood because they are hidden by the formidable screen of stars, dust and gas that comprise the Plane of the Milky Way. Infrared and radio observations have the ability to penetrate this obscuring mask to study and ultimately unlock the secrets within the dark molecular clouds. I will present new results of radio/infrared observations of deeply embedded SNe that we use to study how the interaction between SNe and their birth clouds evolve from the earliest stages to the relatively mature phase in which the remnant settles back into the ISM. The ground observations include near-infrared spectral imaging using the Hale 200" telescope and the 3.9-m Anglo-Australian Telescope. The mid-infrared data are acquired with the Spitzer Space Telescope. The presentation will include some historical perspective on studies of SNe within the Milky Way and beyond to nearby galaxies.
