Pre-Colloquium tea served at 3:45 in the Prowse Room
|First Friday in Fall Semester is September 2|
|September 16|| HONORS CONVOCATION, NO COLLOQUIUM
|September 23|| Properties of exoplanets and systems with Kepler
Jason Steffen (UNLV)
NASA's Kepler mission has revolutionized the field of exoplanets and its discoveries give new insights into our theories of planet formation and dynamical evolution. With over 4000 planet candidates and 1000 confirmed planets, the variety of systems and planets shows the breadth of properties that planet formation models must encompass. I present some of the landmark results of the Kepler mission, especially relating to the planet masses and orbital architectures of the planetary systems. I discuss how these results affect our understanding of the solar system and of planets in general.
|September 30|| Measuring the Universe with the Dark Energy Spectroscopic Instrument
Stephen Bailey (LBL)
The Dark Energy Spectroscopic Instrument (DESI) will perform a spectroscopic redshift survey of ~30 million galaxies and quasars at the Kitt Peak National Observatory 4-m Mayall telescope from 2019-2024. These include 4M luminous red galaxies, 17M emission line galaxies, and 2.4M quasars with 0.7M Lyman-alpha forest lines-of-sight. These enable DESI to map the expansion history of the universe to redshift 3 with unprecedented accuracy using the baryon acoustic oscillation method. During bright time, DESI will observe an additional 10M nearby galaxies and 10M stars. I will describe the science reach of DESI, the new spectrographs fed by 5000 robotically positioned fiber optics, and the data systems for target selection, survey planning, simulations, and processing the data. While building off the heritage of previous galaxy redshift surveys, DESI is upgrading all aspects of the pipelines and algorithms to maximize the science reach of the new instrument and survey.
|October 7|| WIRO OPEN HOUSE, NO ASTRO COLLOQUIUM
|Mon, October 10||Joint Astronomy/Geology Colloquium; Geology 216 at 3:10PM (NOTE day/time/room change)
The Diversity and Demographics of Distant Rocky Worlds
The discovery of exoplanets (planets outside our Solar System) has brought the settings of many science fiction stories within reach of scientific inquiry. Astronomers' ever increasing sensitivity to smaller and smaller planets has opened the opportunity for empirical insights into the nature and demographics of distant terrestrial worlds. Up to what size and mass do planets typically have rocky compositions? How Earth-like are these distant rocky worlds? How common are rocky planets in the Habitable Zones of their host stars? In this talk, I will present the current constraints on each of these questions, appealing both to individual planet case studies and to planet population statistics.
|October 28|| Women in Physics & Astronomy Tea
Join us for a discussion of the status of women in physics & astronomy!
|November 4|| Simulating Plasma in Diverse Environments: Relativistic Jets, Black Hole Accretion, Re-Entry Black Out
and Plasma Opening Switches
Kris Beckwith (Tech-X Corporation)
Computational models of ionized plasmas play a crucial role in understanding the dynamics of a diverse range of systems. Simulation has provided crucial insights into black hole astrophysics, where the interaction of the plasma with the black hole event horizon form relativistic jets that can be observed on galactic scales and black hole accretion, where emergent phenomena in magnetized turbulence gives rise to variability that can be measured using space-based telescopes. Closer to Earth, first-principles computational study of the physics blackout during spacecraft re-entry has provided opportunities to design mitigation devices, while plasma switches for pulsed power applications present opportunities for novel multiscale approaches. In this talk I will highlight results that have been obtained through numerical simulation across this range of fields and describe an effort to develop a fluid-plasma-electromagnetic modelling tool, experimentally validated for re-entry simulation with capabilities for modeling high energy density plasmas. As part of the discussion, I will highlight how these different research paths can be used to build a research career outside of academia.
|November 18|| The Milky Way Project: Citizen Scientists Map Our Home Galaxy
Matthew Povich (Cal. Poly Pomona)
I will tell the history of the Milky Way Project (MWP), which first launched in December 2010 as one of the original ten Zooniverse (www.zooniverse.org) online citizen science programs, and present the results. Tens of thousands of internet users from around the globe have participated in the MWP over the past six years. Using an intuitive set of drawing tools on the MWP website (www.milkywayproject.org), these MWP volunteers make simple drawings and markings on Galactic survey images from the Spitzer Space Telescope to classify various types of astronomical objects. The first MWP data release presented a catalog of more than 5,000 infrared "bubbles" and identified a new class of objects called "yellowballs." The majority of bubbles are H II regions, while the yellowballs are thought to be either proto-bubbles or lower-luminosity star-forming regions. The large catalog of bubbles has enabled statistical studies of the prevalence of triggered star formation in our Galaxy. We are currently working on the second data release of MWP, which will analyze over 3 million classifications to produce an improved bubbles catalog and the first-ever citizen-science catalog of stellar-wind bow shock candidates. The most recent version of MWP, launched on September 15, 2016, has already provided >400,000 classifications and identified numerous new bow shock candidates that were not included in the recently-published catalog of 709 bow shock candidates identified by UW and Cal Poly Pomona astronomers.
|November 25|| THANKSGIVING, NO COLLOQUIUM
|Thur, December 1, 4pm at PS 234||Non-Equilibrium Control of Charge and Spin Motion in QUantum Materials
Hermann Durr (University of Stanford/SLAC)
Understanding the ultrafast interplay between charge, magnetic and lattice degrees of freedom is central to gaining control of condensed matter phenomena as diverse as insulator-metal transitions  and magnetic switching [2-4]. While generally accepted for strongly correlated oxides, the coupling of magnetism with lattice degrees of freedom is not well established for metallic magnetic materials. Especially for non-equilibrium processes leading to laser assisted magnetic switching coupling to phonons is often neglected. Femtosecond soft x-ray pulses from the Linac Coherent Light Source, offer the unique opportunity to image in real time the ultrafast electron and spin dynamics that leads to magnetization reversal  and turns insulators into metals . Hard x-rays and fs electron pulses  enable first glimpses at the laser-induced lattice motion revealing unexpected electron-lattice coupling. Understanding and ultimately engineering the evolving electron, spin and lattice motion on the time- and lengthscales associated with the relevant interactions promises new ways for storing and processing of information.
|Final Friday in Fall Semester is December 9|
|First Friday in Spring Semester is January 27|
|January 27|| On the Edge: Exoplanets with Orbital Periods Shorter Than a Peter Jackson Movie
Brian Jackson (Boise State)
From wispy gas giants to tiny rocky bodies, exoplanets with orbital
periods of several days and less challenge theories of planet
formation and evolution. Recent searches have found small rocky
planets with orbits reaching almost down to their host stars'
surfaces, including an iron-rich Mars-sized body with an orbital
period of only four hours. So close to their host stars that some of
them are actively disintegrating, these objects' origins remain
unclear, and even formation models that allow significant migration
have trouble accounting for their very short periods. Some are members
of multi-planet system and may have been driven inward via secular
excitation and tidal damping by their sibling planets. Others may be
the fossil cores of former gas giants whose atmospheres were stripped
|THURSDAY, February 2, 4:10 PM, Prowse Room 234|| Obscured Quasars in the Cosmic Web: Dark Matter Halos and Unification Models
Michael DiPompeo (Dartmouth College)
With WISE all-sky mid-IR data we can now assemble large obscured quasar samples, allowing us to place them in the context of the growth of cosmic structure and galaxy evolution. Using two independent methods, we find that obscured quasars reside in halos with larger masses than their unobscured counterparts, with implications for evolutionary quasar models. Under the assumption that a subset of the obscured population is indeed obscured by a torus, and otherwise intrinsically identical to the unobscured population, our measurement places a lower limit on the halo masses of obscured quasars that represent a particular evolutionary phase. Using analytical methods and cosmological simulations, we predict the halo masses of this distinct population. Finally, using a simple halo growth model and empirical relationships between halo, stellar, and black hole masses, we show that an evolutionary sequence from obscured to unobscured quasar phases in conjunction with a flux or luminosity limit can not only naturally reproduce our halo mass measurements, but explain some discrepant results in the literature.
|February 10||Noble Metal-Free Electrocatalysts for Water Electrolysis|
Shuo Chen (University of Houston)
Hydrogen is an important precursor for important chemical compounds such as ammonium and methanol. Hydrogen is also considered as a clean fuel. Currently, 95% of hydrogen is produced from non-regenerated fossil fuels. In contrast, approximately 70% of earth surface is covered with water, which provides nearly unlimited hydrogen source. Therefor, efficient and large scale hydrogen production from water splitting is highly desired. In this talk, I will mainly present our recent work using low cost and earth abundant electrocatalysts for electrochemical water splitting for hydrogen production1-4. The electrocatalysts are loaded on commercially available metal foams as robust supports. Both the hydrogen evolution and oxygen evolution activity approach the state-of-the-art noble metal based electrocatalysts. The performance is attributed to high surface area, porous structures, excellent electrical conductivity, favorable electronic structure, and abundant active sites, making them primising to realize large-scale water splitting.
POSTPONED DUE TO WEATHER
To be held in Classroom Building 129
|March 3|| Small Planets Transiting Nearby Small Stars
Zach Berta-Thompson (CU Boulder)
Astronomers have found thousands of new worlds orbiting other stars. These worlds offer an opportunity to explore how planets work in conditions different than those present in our own Solar System. We may be able to better understand the evolution of the atmospheres of small, rocky, planets through spectroscopic observations of some of their atmospheres. However, such measurements will be possible only for those small planets that transit very nearby, very small stars. I will present our efforts with the MEarth Project to find these systems, and I will discuss the landscape for small planet characterization in the TESS and JWST era.
|March 17|| SPRING BREAK, NO COLLOQUIUM
|March 24||Elsevier Author Seminar
Marc N. Chahin (Elsevier)
Good research deserves to be published, to be widely read, and to be recognized by fellow researchers and the community. The current research (and funding) climate makes it necessary that you are successful in being published: "Publish or Perish" is the motto. This raises the question, how can you achieve that goal?
"Success" essentially depends on three components:
|April 7|| Title, TBD|
Sanghamitra Neogi (University of Colorado, Boulder)
|April 14||Women+ in Physics & Astronomy Tea|
|April 18||The Hall Effects Edwin Hall Never Imagined
Xiaofeng Jin (Fudan University, China)
The anomalous Hall effect (AHE) is one of the oldest and most prominent transport phenomena in magnetic materials. However, the microscopic mechanism of the AHE has remained unresolved for more than a century because its rich phenomenology defies standard classification, prompting conflicting claims of the dominant processess. We differentiate these processes through temperature-dependent measurements on epitaxial Fe, Ni, Co, and NixCu1-x films of varying thickness [1,2]. The results allow an unambiguous identification of both intrinsic and extrinsic mechanisms of the anomalous Hall effect. The more recently discovered spin Hall effect (SHE) has attracted a great deal of attention becuase of its potential applications in spin current devices. Various methods have been developed to generate and detect the SHE and search for materials with large spin Hall angles. These efforts notwithstanding, reliable and accurate determination of spin Hall angle remains a challenge. In this lecture I will first give a comprehensive discussion on the basic concepts of AHE and SHE. Exploiting the attributes of epitaxial magnetic thin films, I will then explain how to control independently the different scattering processes through temperature and layer thickness and to identify unambiguously the intrinsic and extrinsic mechanisms of the AHE. Finally, based on the understanding of the microscopic mechanisms of the AHE, I will describe how we developed a new method using H-patterned films to measure quantities inherent in the SHE.
|April 21|| Title, TBD|
Jaremy Creechley (Bright Agrotech, Laramie)
|April 28|| Title, TBD
Phil Hopkins (Caltech)
|May 5|| Title, TBD
Matt Greenhouse (NASA)
|Final Friday in Spring Semester is May 5|