UNLV Department of Physics and Astronomy

Forum Schedule:  Fridays 3:45pm - 4:45pm

DateSpeakerTitle & Abstract
Aug 28
Sep 4
Sep 11
Sep 18
Sep 25
Oct 2Prof. Josh Bloom
(UC Berkeley)
(host: Zhang)
"Transients in the Wide-Field Synoptic Era"
The advent of precursor experiments to the Large Synoptic Survey Telescope (LSST) Project herald a fundamental transition in time-domain astronomy: the data acquisition rates simply swamp the traditional capabilities of astronomers to perform and react to discoveries. New tools are required to abstract humans out of the real-time loop in order to extract novel science from such datastreams. I will discuss the some of scientific aims of the Palomar Transients Factory, the Synoptic All-Sky Infrared Survey (SASIR) and LSST, with a particular focus on rarities and synergies with gravity wave projects. I will also discuss our new NSF Cyber-enabled Discovery Initiative effort to build a computational framework, based in part on parallelized machine-learning algorithms, for classifying time-series data in the context of discovery and follow-up.
Oct 9Dr. Robert Preece
(Univ. of Alabama, Huntsville)
(host: Zhang)
"GRB Observations with the Fermi Gamma-Ray Space Telescope"
After the first 14 months of operations, the Fermi Gamma-Ray Space Telescope has observed over 320 GRBs, including more than 10 by the ground-breaking Large Area Telescope. As with each new capability, the new observations are re-writing the book about what we thought we knew about GRBs as well as raising new questions. In particular, the joint spectroscopy from the two instruments, covering roughly 6 decades in energy, has revealed some remarkable surprises. In particular, there are some interesting limits that can be placed on the level of violation of Lorentz Invariance by high-energy photons.
Oct 16Mr. Krzysztof Nalewajko
(Nicolaus Copernicus Astronomical Center)
(host: Proga)
"Energy dissipation mechanisms in blazars"
I discuss the relevance of studying energy dissipation mechanisms for understanding the emission of blazars. The model of internal shocks has been proven to explain most of the observed activity in blazars. Recently, two phenomena have turned our attention to alternative models. A peculiar outburst of knot HST-1 in the jet of nearby galaxy M87 is most probably a manifestation of reconfinement shocks. The studies of typical length scales, dissipation efficiency and polarization of emission from reconfinement shocks are reported. Observations of fast TeV flares call for processes acting in magnetically dominated inner jet regions. A model of minijets, based on energy dissipation via magnetic reconnection, is presented.
Oct 23Dr. Vojin Joksimovich
(Retired nuclear engineer)
(host: Pravica)
"Nuclear Renaissance"
The following subjects will be specifically addressed: Sources of U.S. electricity, factors driving new construction, remarkable performance of 104 U.S. plants including life-extension, carbon-free U.S. electricity sources, economics of nuclear power, status of new U.S. plants, and availability of nuclear fuel. Obstacles will also be addressed: financing, nuclear waste management and political ones.
Oct 30No ForumNevada Day
Nov 6Dr. Vivienne Wild
(IAP, France)
(host: Nagamine)
"Timing the Starburst AGN Connection"
There are many theories successful in explaining the observed correlations between black holes and their host galaxies. In turn, these theories play a crucial role in explaining many other observed aspects of the galaxy population. However, observational measurements of the interaction of black holes with their hosts remain scarce. I will present results on the growth of black holes in 400 local galactic bulges which have experienced a strong burst of star formation in the past 600 Myr. I will show how the processes at work in this local starburst sample may well be relevant to the co-evolution of black holes and bulges over cosmic time.
Nov 13Dr. Matthew Eichenfield
(host: Zygelman)
"The Interaction of Light and Sound at the Frontiers of Nanotechnology and Quantum Mechanics"
For the first time, mechanics is about to make the quantum leap. Although many quantum systems from single atoms to superconducting Josephson junctions to Bose-Einstein condensates have been studied in great detail, quantum states of mechanical oscillators have remained elusive because of the difficulty in detecting the minute displacements associated with energies of single phonons—on the order of the diameter of a proton. However, a paradigm shift has occurred due to recent advances in the fabrication of nanoscale optical cavities and the all-optical techniques used to detect and manipulate the motion of these cavities. The field of *cavity optomechanics* is now on the verge of preparing and observing quantum states of the mechanical modes of nanoscale optical cavities, which would have “spooky” quantum properties such as the ability to exist between two places without being able to occupy the space between. In this seminar, I will describe how we design nanoscale optical devices to engineer the interaction of light and sound at the nanoscale. I will also explain we will use these devices to extend the field of quantum mechanics to the mechanical motion of nanoscale mechanical oscillators and discuss the novel applications that are emerging from the study of these devices.
Nov 20Dr. Andrew Fruchter
(Space Telescope Science Institute)
(host: Zhang)
"Gamma-Ray Bursts from a Safe Distance"
Gamma-Ray Bursts are explosions of nearly unrivalled brilliance. They can be bright enough to be seen at cosmological distances with the naked eye and can appear to emit the energy of the rest mass of the sun in high-energy photons in a matter of seconds. I will show evidence that most of these bursts, the so-called long, soft bursts, are produced by the collapse of extremely massive stars in galaxies unlike our own, but similar in many ways to our neighbors, the Magellanic clouds. The astrophysical origin of a smaller subset of bursts, the short, hard bursts, remains a mystery, though these seem to be distributed much more like the general population of stars in the local universe. Even if uncertainties surrounding their formation and emission mechanisms remain, both types of bursts may prove useful cosmological probes in the years ahead.
Nov 27No ForumThanksgiving Holiday
Dec 4Prof. Massimo Ricotti
(Univ. of Maryland)
(host: Nagamine)
"The First Galaxies and the Likely Discovery of their Fossils in the Local Group"
In cold dark matter cosmologies, small mass halos outnumber larger mass halos at any redshift. However, the lower bound for the mass of a galaxy is unknown, as are the typical luminosity of the smallest galaxies and their numbers in the universe. The answers depend on the extent to which star formation in the first population of small mass halos may be suppressed by radiative feedback loops operating over cosmological distance scales. If early populations of dwarf galaxies did form in significant number, their relics should be found today in the Local Group. These relics have been termed ``fossils of the first galaxies''. I will summarize our ongoing efforts to simulate and identify these fossils around the Milky Way and Andromeda. We believe that current observational data support the thesis that a fraction of the new ultra-faint dwarfs recently discovered in the Local Group are in fact fossils of the first galaxies. Finally, we discuss a physical mechanism that could turn small mass dark halos, too small to form stars before reionization, into gas-rich but starless ``dark galaxies''.
Dec 11

Past forums: Fall '08   Spring '09