February 29, 2016 3:30 BPB-217. Candidate: Zhaohuan Zhu. From Protoplanetary Disks to Exoplanets: Theory Confronts Observations.

We are entering a golden era of study in the field of planet formation. Recently commissioned telescopes and instruments (e.g., Subaru, GPI, VLA, ALMA, EVLA) are now finally able to resolve the protoplanetary disk down to the scale of a planet's immediate assembly zone, and a rich variety of disk features have been revealed: gaps, large scale disk asymmetry, and spiral arms. Despite this progress on the observational front, theoretical models have yet to be developed that can reveal what these observations are telling us about the physics of disk structure and planet formation. In this talk, I will present my work on numerical simulations of planet-disk interaction, with an emphasis on understanding current observations. My simulations have not only successfully reproduced observed spiral arms, gaps and asymmetric features, but also constrained protoplanetary disk properties and revealed potential planets in these disks. To directly find young planets, I will suggest that disks around these forming planets, so-called circumplanetary disks, could be the key and we may have already found some circumplanetary disk candidates. Finally, I will discuss how the new generation of numerical codes and simulations I am working on are important for not only interpreting upcoming observations but also revealing fundamental physical processes in protoplanetary disks. Combining the new generation of observations and simulations, we may finally unveil the mystery of planet formation in the next decade.

February 26, 2016 3:30 BPB-217. Anna Barnacka. Resolving the High Energy Universe with Strong Gravitational Lensing.

Gravitational lensing is a powerful tool for elucidating the origin of gamma-ray emission from distant sources. Cosmic lenses magnify the emission and produce time delays between mirage images. Gravitationally-induced time delays depend on the position of the emitting regions in the source plane. Temporal resolution at gamma-ray energies can be used to measure these time delays, which, in turn, can be used to resolve the origin of the gamma-ray flares spatially. As a prototypical example of the power of lensing combined with long, uniformly sampled light curves provided by the Fermi satellite, we investigated the spatial origin of gamma-ray flares from two known gravitationally lensed sources: PKS 1830-211 and B2 0218+35.

February 25, 2016 3:30 BPB-217. Candidate: Ivan Ramirez. High-precision spectroscopy: from exoplanets to Galactic chemical evolution.

Stellar spectra contain a wealth of information, but they can be difficult to interpret due to modeling limitations. Over the past few years, a new technique that circumvents these limitations and allows astronomers to determine atmospheric parameters and elemental abundances of stars with unprecedented precision (~1%) has been developed by me and my collaborators. Using this technique, we have discovered that the Sun has a peculiar chemical composition, one which can be interpreted as a signature of the formation of the solar system. We can use this technique to infer the presence and bulk composition of planets around other stars. Moreover, it allows us to peer into the formation histories of stars and how they could affect planet formation. In addition to being useful for exoplanet research, these data sets are also well-suited for studies of nucleosynthesis and the chemical evolution of our Milky Way galaxy. In this talk I will describe the methods and key results that we have obtained using high-precision stellar spectroscopy.

February 22, 2016 3:30 BPB-217. Candidate: Daniel Perley. The Environments of the Universe's Most Extreme Explosions Across Cosmic History.

Massive stars have been known to end their lives violently for almost a century, but the extremes of this process have become appreciated only recently: rare classes of "superluminous" supernovae are hundreds of times more luminous than other SNe, and long-duration gamma-ray bursts fleetingly outshine the brightest quasars by orders of magnitude. Their immense luminosities make these events easily detectable from great distance, from which they can serve as probes of the high-redshifts IGM, ISM, and rate and sites of cosmic star-formation. However, employing them as tools in this way requires a thorough understanding of how varying conditions such as metallicity may favor or disfavor their production in different environments. I will discuss two large surveys I am leading to study the connection between extreme transients and their galaxy environments: SHOALS, a multi-observatory effort to examine the impact of galaxy evolution on the GRB rate and host population across cosmic history, as well as the PTF superluminous-supernova host project at Keck and Palomar. Extreme transients will be discovered at a much wider range of distances and greater numbers in the coming era of all-sky synoptic surveys, and studies of these events and their environments with existing and upcoming facilities will prove invaluable for understanding the composition and evolution of dwarf galaxies, the history of the early universe, and theories of massive-stellar evolution and variations in the IMF.

February 11, 2016 3:30 BPB-217. Candidate: Norbert Werner. Sculpting the Visible Universe.

In the course of structure formation, only a small fraction of the baryons turned into stars - most remain in a diffuse intergalactic medium. The growth and evolution of galaxies is controlled by feedback processes, such as energy and momentum input from supernovae, and from the jets and winds of accreting supermassive black holes. I will start my talk by presenting observational results on the role of supermassive black holes in suppressing star formation in the most massive galaxies, keeping them 'red and dead'. Then, I will show how deep observations of extreme clusters of galaxies inform us about the microphysics of the intergalactic medium, which determines how the energy from accreting black holes couples with the diffuse gas. Then, I will 'zoom out' to the outskirts of galaxy clusters where we also find hints that supermassive black holes played an important role in the distant past. X-ray observations reveal a remarkably homogeneous distribution of iron out to the virial radius of the nearby Perseus Cluster, requiring that most of the metal enrichment of the intergalactic medium occurred before the cluster formed, probably more than ten billion years ago, during the period of maximal star formation and black hole activity. Finally, I will talk about the upcoming ASTRO-H satellite which will revolutionize X-ray spectroscopy and our understanding of the physics of galactic feedback.

Jared Rice wins NVSGC Graduate Research Fellowship

Jared Rice was awarded a prestigious Nevada NASA Space Grant Consortium Graduate Research Opportunity Fellowship in the amount of $21,000 for the 2015/2016 academic year. The NVSGC GROF supports Jared and his advisor Dr. Bing Zhang on their latest project on the characteristics of high-redshift tidal disruption events. Their proposal entitled "Tidal Disruption Events in the Early Universe" was selected by NVSGC as one of the top applications of the year across the state of Nevada. The fellowship is a 1:1 match from NVSGC and the UNLV Department of Physics and Astronomy. More details may be found on the NVSGC fellowship recipients page:

2015-2016 Fellowship Recipients

February 12, 2016 3:30PM BPB-207. Shanti Deemyad. Lithium under pressure.

Even at zero temperature lattice of lithium remains far from static. In periodic table lithium is the first element immediately after helium and the lightest metal. While fascinating quantum nature of condensed helium is suppressed at high densities, because of the presence of long range interactions in metallic systems, lithium is expected to adapt more quantum solid behavior under compression. Physics of dense lithium offers a rich playground to look for new emergent quantum phenomena in condensed matter. In this talk I will discuss the physics of ultra-light materials under extreme pressures and will present some of our studies on unraveling the physics of dense lithium.