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|Thu, Jan 09|
|no colloquium (AAS meeting).
|Thu, Jan 23|
Pennsylvania State University
"Precise Radial Velocities for the Future"
As precise radial velocimetry passes the 20 year mark, it remains a fundamental component of the exoplaneteer's toolkit. I will look ahead to the role it will play in its third decade, characterizing the Kepler mission's extraordinary harvest of planetary systems, exploring the Solar neighborhood, and placing the Solar System in cosmic context. I will describe our strategy with the MINERVA project and at the Hobby-Eberly Telescope, which proceeds both from the"outside in" and the "inside out". Long-term followup of Kepler systems with inner terrestrial planets will reveal their larger architecture, including the Jupiter analogs that dynamically craft and stabilize planetary orbits. High cadence monitoring of the brightest, nearest, most Sun-like stars will burrow beneath the astrophysical and instrumental noise to reveal the close-in terrestrial planets orbiting stars already known to have outer gas giants.
|Thu, Jan 30|
Lawrence Berkeley Lab
"Tracing Large Scale Structure with the Lyman alpha Forest"
The Baryon Oscillation Spectroscopic Survey (BOSS) uses the SDSS telescope to obtain spectra of 1.5 million galaxies to get very accurate measurements of the Baryon Acoustic Oscillations (BAO) scale at redshift z ~0.5. Roughly 20% of the fibers of the spectrograph, however, are pointing to high redshift quasars with the goal of detecting the BAO in the clustering of gas responsible for the Lyman alpha absorption present in the quasar spectra, known as the Lyman alpha forest. In this talk I will overview several recent results from the Lyman alpha forest working group in BOSS, including the measurement BAO at z=2.4 both from the auto-correlation of absorption, and from its cross-correlation from quasars. I will also comment on other interesting science that can be done with the data, like studying quasar radiation models or measuring the amplitude of matter fluctuations in very small scales from the line of sight power spectrum.
|Thu, Feb 13|
"Quantifying High-Redshift Star Formation with Gamma-Ray Bursts"
One of the most exciting broader applications of the study of gamma-ray bursts is in better understanding the star-formation history of the Universe. Long-duration GRBs are produced exclusively by massive, young stars and can be detected beyond z>8, pinpointing a star formation rate-selected sample of galaxies independent of galaxy luminosity spanning nearly all of cosmic history. On the other hand, GRB selection may introduce new biases, both intrinsic (such as a dependence on metallicity) and observational (the galaxy may be difficult to pinpoint if the GRB afterglow is dust-obscured). I will discuss recent efforts to shine light upon GRBs and their hosts via an observational campaign designed to evaluate the differences between GRB and star-formation rates and their redshift evolution out to z=3 and beyond, with particular emphasis on the importance of accounting for the impact of dust extinction. New results from large GRB host surveys ongoing at Spitzer and major ground-based facilities will provide unique insight into the combined evolution of cosmic metal abundance and the star-formation rate across the Universe's history.
|Thu, Feb 20|
"The New Era of Exoplanet Direct Imaging"
Most of the hundreds of extrasolar planets identified in the past 15 years have been detected indirectly---through careful monitoring of the planets' effect on their host star's light. By overcoming the extremely large brightness contrast between the stars and their faint exoplanetary companions, we are now able to actually image wide-separation exoplanets using large ground-based observatories such as Keck, VLT, and Gemini. I will describe in detail a new generation of astronomical instruments dedicated to this task, spanning observatories across two hemispheres. These instrumentation platforms will allow us to extract detailed spectroscopic information about exoplanets, providing insight into the atmospheric chemistries, compositions, and thermodynamic properties of these objects. I will also highlight how we are using completely new discoveries of circumstellar debris disks, analogs of our own Kuiper belt, as signposts for the discovery of new exoplanetary systems. Efforts such as these will allow us to detect and characterize the youngest exoplanetary systems with the ultimate goal of creating a coherent picture of their formation. If time allows, I will discuss a separate effort at Keck to investigate those systems with planetary orbits that are misaligned from their stellar spin axes with some surprising results.
|Thu, Feb 27|
"Seeing Gravitational Waves: Transients in the Local Universe"
The advent of wide-field synoptic imaging has re-invigorated the venerable field of time domain astronomy. Our framework of optical transients no longer has a wide six-magnitude luminosity "gap" between the brightest novae and faintest supernovae. Multiple new and distinct classes of very rare explosions have been uncovered just in the past few years. I review the surge of excitement (and debate) on the physics of these transients with unprecedented explosion signatures. "Gap transients" represent missing pieces in two fundamental pictures: the fate of massive stars and the evolution of compact binaries. Calcium-rich gap transients may even be the key to solving a long standing abundance problem in the intra-cluster medium. Two classes of gap transients are extremely red, hinting that the infrared dynamic sky is ripe for exploration. I conclude with the next frontier in gap transients --- discovering elusive binary neutron star mergers, a goal which may soon be within reach with coordination between the next generation of synoptic surveys and advanced gravitational wave interferometers. This search may literally be the 21st century gold rush!
|Thu, Mar 06|
"Astronomy at the Edges: Forty Years of Eclectic Projects at the University of Washington"
This talk will be a retrospective look, upon my official retirement, at a potpourri of projects in which I've participated. These interdisciplinary projects have not involved "standard" astronomical research, but rather the astronomical aspects of other avenues of inquiry - Icall it "Astronomy at the Edges." My research in history of astronomy has been the major example in my career, but having given a colloquium about this two years ago, I will focus on other topics this time. There have been several such "Edgy" projects related to the Search for Extraterrestrial Intelligence (SETI), including (1) the launch of seti@home in 1999, the first distributed computing project involving the public, (2) the "radio signature of the Earth," involving the calculation of exactly how our civilization would appear to an eavesdropping alien radio astronomer (1978), (3) "Earth at Night" (1986), the first complete view of the night-time Earth as seen through its manmade light leakage to satellites,and (4) the design for the Dept. of Energy of a system of markers to warn for the next 10,000 years of the dangers of a nuclear disposal site in New Mexico (1992). Finally, in 1998 a group of us founded the multi-department, graduate UW Astrobiology Program, the first such program and still the best in the world. The second major area of Edgy projects is in the world of gnomonics, the art and science of sundials. Starting with the large wall sundial on the UW Physics/Astronomy Building (1994), an irrational exhuberance for sundials has resulted in the design and installation of ~20 unique public sundials, mostly in the Seattle region, but also located in San Francisco, at the Very Large Array in New Mexico, andon each of the Mars Rovers (2004- ). Time-lapse animations of the UW dial and the MarsDials will be shown.
|Thu, Mar 13|
"Dark Matter Signals from the Inner Galaxy?"
Dark matter makes up roughly 80% of the matter in the universe, yet the details of its particle nature remain unknown. Many particle dark matter candidates can pair annihilate or decay to produce Standard Model particles, including gamma rays, charged particles, and neutrinos. The detection of these indirect signals of the annihilation or decay of dark matter in our Galaxy and beyond is a promising method for identifying dark matter, understanding its intrinsic properties, and mapping its distribution in the universe. Recent indirect searches with gamma rays have yielded several tantalizing hints of dark matter signals from the Inner Galaxy, however a confident detection remains elusive. I will discuss these recent results and possible alternatives to the dark matter interpretation of the claimed signals, as well as new approaches and prospects for robustly identifying a dark matter signal from the Inner Galaxy with upcoming experiments.