University of Wyoming Physics & Astronomy Colloquium Series

Fridays -- 4:10 PM -- Prowse Room 234

Pre-Colloquium tea served at 3:45 in the Prowse Room

Fall 2016 & Spring 2017 Schedule

First Friday in Fall Semester is September 2
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.

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
Leslie Rogers (University of Chicago)

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 ( 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 (, 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.

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 [1] 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 [4] and turns insulators into metals [1]. Hard x-rays and fs electron pulses [5] 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.
[1] S. de Jong et al., Nature Materials 12, 882 (2013).
[2] I. Radu, et al., Nature 472, 206 (2011).
[3] C.-H. Lambert, et al., Science 345, 1337 (2014)
[4] C. E. Graves, et al., Nature Materials, 12, 293 (2013)
[5] T. Chase, et al., Appl. Phys. Lett. 108, 041909 (2016).

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 by tides.

In this presentation, I'll discuss the work of our Short-Period Planets Group (SuPerPiG), focused on finding and understanding this surprising new class of exoplanets. We are sifting data from the reincarnated Kepler Mission, K2, to search for additional short-period planets and have found several new candidates. We are also modeling the tidal decay and disruption of close-in gaseous planets to determine how we could identify their remnants, and our results suggest the cores have a distinctive mass-period relationship that may be apparent in the observed population. Whatever their origins, short-period planets are particularly amenable to discovery and detailed follow-up by ongoing and future surveys, including the TESS mission.

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.

[1] Haiqing Zhou, Fang Yu, Yufeng Huang, Jingying Sun, Robert J. Nielsen, William A. Goddard III, Shuo Chen, and Zhifeng Ren, "Efficient hydrogen evolution by ternary molybdenum sulfoselenide MoS2(1-x)Se2x particles on self-standing porous NiSe2 foam", Nature Commun. 7, 12765 (2016).
[2] Haiqing Zhou, Fang Yu, Jingying Sun, Ran He, Yumei Wang, Chuan Fei Guo, Feng Wang, Yucheng Lan, Zhifeng Ren, and Shuo Chen, "Highly active and durable self-standing WS2/graphene hybrid catalysts for hydrogen evolution reaction", J. Mater. Chem. A 4, 9472-9476 (2016).
[3] Haiqing Zhou, Yumei Wang, Ran He, Fang Yu, Jingying Sun, Feng Wang, Yucheng Lan, Zhifeng Ren, and Shuo Chen, "One-step synthesis of self-supported porous NiSe2/Ni hybrid foam: An efficient 3D electrode for hydrogen evolution reaction", Nano Energy 20, 29-36 (2016).
[4] Fang Yu, Haiqing Zhou, Zhuan Zhu, Jingying Sun, Ran He, Jiming Bao, Shuo Chen, and Zhifeng Ren, "Three-dimentional nanoporous iron nitride film as an efficient electrocatalyst for water oxidation", ACS Catalysis under revision.

February 24 Classroom Building 129 The 14-billion Year History of the Universe Leading to Modern Materials Science
Joe Greene (UIUC, Linköping, NTU)

POSTPONED DUE TO WEATHER Abstract is available here

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 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:

  1. The ability to determine the best possible publication strategy for your research findings.
  2. The best possible way to write your article.
  3. The most effective interaction with editors. Key to success in this context is your ability to put yourself in the position of readers, reviewers and editors.
Important considerations in journal selection are a realistic assessment of the quality of the research and of the audience you intend to reach. The art of manuscript writing is not just applying one "golden tip". It is essentially telling your story to your readers in an engaging way, and avoiding common mistakes and deficiencies including poor languaage. Avoidable mistakes can lead to unnecessary rejection of your manuscript. Finally it is your open attitude towards the editors and the reviewer comments, that will not only increase the likelihood of getting your manuscript accepted for publication, it is also likely that your published paper has improved thanks to their comments. By consistently applying these principles, and by understanding the publishing process and the editors' and reviewers' expectations, you are likely to become a more successful author.

April 7 Thermal Transport at the Nanoscale: How to Control the Quanta of Energy?
Sanghamitra Neogi (University of Colorado, Boulder)

Quantized vibrations in condensed phases, phonons, obey the laws of quantum mechanics in the same way as electrons and photons, that are commonly exploited as energy and/or information carriers. Efforts to achieve control of phonons over a broad range of scales, especially at micro- and nanoscale have been simulated by the ever increasing roles that phonons assume via interacting with electrons and photons, in a very broad range of technological applications, encompassing nanoelectronics, renewable energy harvesting, nano- and opto-mechanics, quantum technologies, and medical therapy, imaging and diagnostics. Phonon engineering has seen rapid progress through understanding of structure-processing-property relationships that connect nanoscale structures, dictated by methods of fabrication and processing, and vibrational and thermal transport properties.
In this seminar, I will present an overview of thermal transport in nanostructured materials, with special emphasis on the role of defects, surfaces and interfaces on energy transport. I will discuss an illustrative example of phonon engineering in nanostructured ultrathin silicon membrances. Surface nanoscale structures have a one-to-one relationship with engineered phonon dispersions: rough layers of native oxide at surfaces limit the mean free path of thermal phonons. The presence of surface nanostructures, by means of pattern formation and surface oxidation, results in a 40-fold reduction in the in-plane thermal conductivity of the membrances, while preserving their electronic properties. Our results guide materials design for future phononic applications, setting the length scale at which nanostructuring affects thermal phonons most effectively.

April 14 Women+ in Physics & Astronomy Tea
April 18
Classroom Building 118
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.

  1. Y. Tian, L. Ye, and X. Jin, "Proper scaling of the anomalous Hall effect," Phys. Rev. Lett. 103, 087206 (2009), doi: 10.1103/PhysRevLett.103.087206
  2. D.-Z. Hou, G. Su, Y. Tian, X. Jin, S. A. Yang, and Q. Niu, Phys. Rev. Lett. 114, 217203 (2015), doi: 10.1103/PhysRevLett.114.217203.

April 21 Life after Physics: The Process of Becoming an Engineer
Jaremy Creechley and Brian Scoggins (Bright Agrotech, Laramie)

For the graduating classes of 2011 and 2012, about 43% of new physics and astronomy graduates joined the workforce. Of those, only 3% took roles explicitly connected to physics and astronomy. Most became engineers (source: American Physics Society). Two alums of the UW Physics & Astronomy Dept., Jaremy Creechley and Brian Scoggins, work for the Laramie-based start-up Bright Agrotech share their experiences as members of that 43%, and the process of transitioning from pure-science in academia to engineering and computer science. They also examine how their backgrounds, interests, and experience at UW informed that transition and eventual arrival at Bright, using some current and past projects as examples.

April 28 Stars Re-Shaping Galaxies
Phil Hopkins (Caltech)

The most fundamental unsolved problems in galaxy formation revolve around "feedback" from massive stars and black holes. I'll present new results from the FIRE simulations which combine new numerical methods and physics in an attempt to realistically model the diverse physics of the interstellar medium, star formation, and feedback from stellar radiation pressure, supernovae, stellar winds, and photo-ionization. These mechanisms lead to 'self-regulated' galaxy and star formation, in which global correlations such as the Schmidt-Kennicutt law and the global inefficiency of star formation -- the stellar mass function -- emerge naturally. Within galaxies, feedback regulates the structure of the interstellar medium, but more radically drives outflows which can actually change the dynamics, morphologies, and sizes of galaxies, in addition to transforming cusps into cores and suppressing star formation. We are actually reaching the point where different stellar feedback and stellar types can produce observable differences on extra-galactic scales. Finally, I'll discuss where stellar feedback fails, and additional feedback, perhaps from AGN, is really needed to explain observations.

May 5 The James Webb Space Telescope Mission
Matt Greenhouse (NASA)
4:00 pm in CR 129!

The James Webb Space Telescope is the scientific successor to the Hubble Space Telescope. It is a cryogenic infrared space observatory with a 25 m2 aperture telescope that will extend humanity's high angular resolution view of the universe into the infrared spectrum to reveal early epochs of the universe that the Hubble cannot see. The Webb's science instrument payload includes four cryogenic near-infrared sensors that provide imagery, coronagraphy, and spectroscopy over the near- and mid-infrared spectrum. The JWST is being developed by NASA, in partnership with the European and Canadian Space Agencies, as a general user facility with science observations to be proposed by the international astronomical community in a manner similar to the Hubble. The Webb's construction and integration are complete. The final stages of pre-flight testing is underway in all areas of the program. The JWST is on schedule for launch during late 2018. Brief bio

August 25 The 3π Hα Census of the Local Universe
David Cook (CalTech)


Final Friday in Spring Semester is May 5

Previous colloquia series: Fall 2002 Spring 2003 Fall 2003 Spring 2004 Fall 2004 Spring 2005 Fall 2005 Spring 2006 Fall 2006 Spring 2007 Fall 2007 Spring 2008
2008-09 2009-10 2010-11 2011-12 2012-13 2013-14 2014-15 2015-16
Contact for program information: Adam Myers