Tuesday, 17 November 2015

Ultrafast Optical Sampling and its Applications in Spectroscopy, Metrology, and Imaging 

Speaker: Dr. Lingze Duan (UAH/Physics)
Location: OPB 234, 2:30pm
Abstract: Recent advance in ultrafast laser technology has enabled high-speed sampling of optical signals and created new frontiers in optical sensing. In this talk, I will introduce the concepts of two optical sampling approaches, asynchronous optical sampling (ASOPS) and optical sampling by cavity tuning (OSCAT), and discuss their applications in spectroscopy, metrology and imaging.

Tuesday, 10 November 2015

Using Strong Gravitational Lensing to Identify Fossil Group Progenitors (25 minutes)

Speaker: Lucas Johnson (UA)
Location: OPB 234, 2:30pm
Abstract: Fossil galaxy systems are thought to be the end result of group evolution, as galaxies experiencing dynamical friction sink to the center of the group potential and merge into a single elliptical that dominates the rest of the members in both mass and luminosity. However, two alternate formation mechanisms are possible: a group merger scenario where two smaller group BGG’s merge into one large elliptical which then promotes the final group to fossil status or the group being initially "born that way". The group merger mechanism could explain why some fossils exhibit cool cores while others do not, as gas cooling timescales are significantly longer than galaxy merging timescales. Most fossil systems discovered lie within z<0.2, which begs the question: what did these systems look like in the past, and which formation process did they undergo? Such progenitors are expected to be systems with imminent or ongoing major mergers that will transition into fossil status before z=0. The dominance of the fossil BGG, or group merger scenario (particularly along the line-of-sight), suggests a highly concentrated system ideal for strong gravitational lensing. Strong lensing events also preferentially pick out merging systems which makes this an ideal selection criteria for our study. We use the CASSOWARY survey of strong lensing events as our sample with the goal of determining if lensing systems have a predisposition of being fossil systems or progenitors. Here we present a catalog of fossil progenitor candidates from the CASSOWARY catalog with redshifts ranging from 0.1>z>0.7 along with some of their properties. We find that 55% of these lensing groups are either fossils or fossil progenitors, suggesting that searching for strong lensing events may be a more efficient way of finding fossil and pre-fossil systems. Follow up Chandra observations of eight progenitors have been scheduled and will show how the hot gas evolves over time during fossil group formation.

The Dense and the Fluffy: X-ray Properties of Extreme Mass Density Elliptical Galaxies (25 minutes)

Speaker: Chris Spradlin (UAB)
Location: OPB 234, 2:30pm
Abstract: Examination of nearby elliptical galaxies yields a relative dearth of superdense galaxies (SDG) -- luminous, yet highly compact galaxies with small half-light radii -- when compared to surveys at z > 1.5, with much debate over how high-redshift SDGs transformed into normal nearby galaxies. Among normal nearby elliptical galaxies, while there exists a high correlation between near-infrared K-band and hot gas X-ray luminosities, there exists a difference of as much as 100 between the X-ray luminosities for a given K-band luminosity. In this work, we perform the first X-ray study of the few low-redshift SDGs that remain, in order to compare their hot gas X-ray properties to normal nearby ellipticals. We utilize the WIde-field Nearby Galaxy-cluster Survey (WINGS) to obtain key parameters in determining the stellar mass densities of these nearby SDGs and complimentary observations made using the Chandra X-ray Observatory to examine the extent of the galaxies' hot interstellar media. We also identify a population of galaxies that have very low stellar mass densities which we call superfluffy galaxies (SFG), and determine their X-ray properties as well.

Tuesday, 3 November 2015

The Culture and Language of Calibration

Speaker: Dr. John McClain (US Army)
Location: OPB 234, 2:30pm
Abstract: Experimental physicists leave school with some general idea of how to function in a laboratory environment. However, every industry, just like every community, has its own culture, language, and customs and it’s important for new members to quickly learn the expectations of each. Guiding basic physics principles employed in calibration labs are presented including nomenclature, types of standards, and the importance of measurement uncertainties. Aspects of the Army’s calibration program are discussed with particular attention given to the role a physicist is expected to play in this environment. Specific standards and calibration examples are given from the field of Radiometry/Photometry. Finally, a review of current and potential research projects in photonic calibration standards is presented.

Tuesday, 27 October 2015

Small-scale Structure and Dynamics of Sunspots and Related Solar Physics Topics

Speaker: Dr. Sanjiv Tiwari (NASA MSFC)
Location: OPB 234, 2:30pm
Abstract: Sunspots are the darkest feature on the visible surface of the Sun, owing to the presence of strong magnetic field in them suppressing convection, the mechanism which transports energy from beneath. After briefly introducing the sunspot magnetic activity cycle, I will describe some of the latest progress in understanding of the thermal, velocity and magnetic small-scale structure as well global properties and dynamics of sunspots. A mature sunspot consists of a dark central umbra surrounded by a less-dark penumbra. The penumbra is composed of copious thin, radially elongated filaments, which are responsible for heat transport. Their structure is at the limit of resolution. We present a unified observational picture of a sunspot penumbral filament, using data from Solar Optical Telescope/Spectropolarimeter onboard the Hinode. The picture is consistent with the penumbral filaments being magneto-convection cells, in line with recent MHD simulations. The observed structure of penumbral filaments provides a natural explanation to a number of long-running controversies in the literature, e.g. whether more horizontal (inter-spine) or more vertical (spine) fields are brighter, whether the Evershed flow takes place in dark or bright strands of penumbra etc. The sunspot umbra and the spines of penumbra show striking similarity in their physical properties albeit with some quantitative differences. The scatter plots of the physical parameters over the full sunspot show a qualitative similarity to those of the standard penumbral filament and its surrounding spines. Our results suggest that spines and penumbral filaments are the only basic elements forming a sunspot penumbra.

On the basis of the abovementioned internal structure of penumbral filaments, we propose a modified picture of formation of penumbral microjets, dynamic events in the chromosphere, which have been proposed to drive coronal heating above them. Another dynamic event we will briefly discuss is penumbral bright dots, observed recently by IRIS and Hi-C. We will discuss an idea of how heating of active region (AR) coronal loops might depend on magnetic setting of their foot points. I will also show that the global magnetic nonpotentiality of an AR determines the speed of the fastest CMEs that an AR can produce, which are drivers of severe space weather.


Tuesday, 20 October 2015

Ultraluminous X-ray Sources in the Nearby Universe

Speaker: Dr. Andrew Sutton (NASA MSFC)
Location: OPB 234, 2:30pm
Abstract: Ultraluminous X-ray sources are accreting black holes detected in nearby galaxies. As their name implies, they are much brighter (and rarer) than typical sources observed in our Galaxy. As such, they can only be explained by either a new class of intermediate-mass black holes, which could be cosmologically-important as the seeds of the supermassive black holes we see today, or they represent a new regime of extreme accretion onto more typical stellar-remnant black holes, thus offer a unique window in which to explore exotic accretion processes. I will review recent observational results in the field and present the state-of-the-art understanding of the nature of these enigmatic sources.


Tuesday, 13 October 2015

The Effects of Deep Turbulence in the Atmosphere on Propagating Laser Beams and how to Characterize and Correct these Effects

Speaker: Dr. Chris Davis (UMD)
Location: OPB 234, 2:30pm
Abstract: When laser beams propagate on relatively long paths (1-5 km) in the low atmosphere they experience what is called “deep” turbulence. The laser beam becomes severely distorted, and breaks into multiple patches. The characterization and correction of these effects is very important for free space optical communication systems and for laser weapons systems. This talk will describe the use of plenoptic sensors and the phenomenon of enhanced backscatter for characterizing the beam distortions and providing information to an adaptive optics system to correct these distortions. The challenges of using coherent combining of high power lasers as a means for correcting overall beam distortion on a distant target will also be discussed.


Tuesday, 6 October 2015

Cassini Infrared Observations of Saturn and its Satellites

Speaker: Dr. Mian Abbas (MSFC)
Location: OPB 234, 2:30pm
Abstract: This seminar will focus on a detailed evaluation of the isotopic distribution of 18O12C16O and its ratio to the standard C16O2 abundance in Saturn’s atmosphere, as retrieved from the infrared observations made by the Composite Infrared Spectrometer (CIRS) on the Cassini mission. The instrument has been providing very valuable infrared spectra in the far and middle spectral regions extending over 10 -1400 cm-1 range, with variable spectral resolutions of 0.53 to 15 cm-1, for global observations of Saturn’s atmosphere and its satellites. Radiative transfer models and non-linear spectral inversion techniques employed for analysis of the infrared observations of Saturn’s atmosphere provide knowledge of the thermal structure and atmospheric constituent distributions of various atmospheric constituents, including some isotopic species. The unexpectedly high C16O2 densities in Saturn’s atmosphere, retrieved from analysis of the observed data, have implications of unspecified external sources, and have been discussed in previous publications. The focus of this presentation is on evaluation of the 18O12C16O distribution in Saturn’s atmosphere from Cassini/CIRS observations in conjunction with the related analytical results of C16O2 , with the objective to acquire a knowledge of fundamental interest relating to the oxygen isotopic ratios of 18O/16O in Saturn’s atmosphere, and other various atmospheric constituents, including some isotopic species. The unexpectedly high C16O2 & C18O2 densities in Saturn’s atmosphere, retrieved from analysis of the observed data, have implications of unspecified external sources.

Tuesday, 29 September 2015

From Dark Matter to Galaxies: Probing the Spatial Structure of the Universe on Small Scales

Speaker: Dr. Andreas Berlind (Vanderbilt)
Location: OPB 234, 2:30pm
Abstract: The last decade has seen an explosion of high precision measurements of the structure of the universe, courtesy of large galaxy surveys such as the Sloan Digital Sky Survey (SDSS). Galaxy clustering measurements encode information about the nature and abundance of dark matter and dark energy, as well as the complex physical process of galaxy formation. However, harnessing the full constraining power of the data is very challenging since it requires a detailed understanding of the statistical and systematic uncertainties in both data and models, which in turn demands significant computational effort. I will discuss my ongoing research program to analyze SDSS data and model it with the help of cosmological N-body simulations, highlighting results from both recent and ongoing projects.


Tuesday, 22 September 2015

Newly Discovered Young Planets Constrain Formation and Migration Theories

Speaker: Dr. Russel White (GSU)
Location: OPB 234, 2:30pm
Abstract: Our understanding of planet formation and migration is limited by both the poorly constrained ages of young stars and the dearth of known planets orbiting them. I'll present results from two observation programs that directly address these. The first uses Georgia State's CHARA Array to measure the angular sizes of young stars, permitting more robust age estimates. The second is a multi-wavelength radial velocity search for young and adolescent age planets. Our discoveries include the first hot- and warm-Jupiters in the nearest open clusters.


Tuesday, 15 September 2015 Special Seminar

Mathematica 10 in Education and Research

Speaker: Troy Schaudt (Wolfram)
Location: OPB 234, 10:30 - 11:30am
Abstract: This talk illustrates capabilities in Mathematica 10 and other Wolfram technologies that are directly applicable for use in teaching and research on campus. Topics include:

  • Enter calculations in everyday English, or using the flexible Wolfram Language
  • Visualize data, functions, surfaces, and more in 2D or 3D
  • Store and share documents locally or in the Wolfram Cloud
  • Use the Predictive Interface to get suggestions for the next useful calculation or function options
  • Access trillions of bits of on-demand data
  • Use semantic import to enrich your data using Wolfram curated data
  • Easily turn static examples into mouse-driven, dynamic applications
  • Access 10,000 free course-ready applications
  • Utilize the Wolfram Language's wide scope of built-in functions, or create your own
  • Get deep support for specialized areas including machine learning, time series, image processing, parallelization, and control systems, with no add-ons required

Current users will benefit from seeing the many improvements and new features of Mathematica 10, but prior knowledge of Mathematica is not required.

Tuesday, 15 September 2015

Standoff Raman Technique for Chemical Sensing

Speaker: Dr. Anup Sharma (AAMU)
Location: OPB 234, 2:30pm
Abstract:  The seminar will summarize our research involving the standoff Raman technique for the Army and the Department of Homeland Security. The technique has been used by us for sensing of chemicals used for making explosives from a distance of up to 250 meters. Stand-off Raman technique can also detect food contaminants/adulterants which could be toxic from a safe, non-contact distance of several meters. Examples include detection of Economically Motivated Adulteration in food items like milk and edible oils. The results show a potential to solve issues related to monitoring food-supply chain and characterize the nature of vulnerability.

Tuesday, 8 September 2015

Engaging Students in the Learning Process

Speaker: Dr. Carol Strong (UAH/Physics)
Location: OPB 234, 2:30pm
Abstract: How to make sure your students are getting the most out of lectures, workshops, and experiments.


Tuesday, 1 September 2015

The Dawn of Gravitational Wave Astrophysics

Speaker: Dr. Tyson Littenberg (UAH/CSPAR)
Location: OPB 234, 2:30pm
Abstract: For decades direct detection of gravitational waves has promised to revolutionize our understanding of the universe. That promise is now poised to become a reality. Ground-based interferometers have completed major upgrades and will resume observations in just a few weeks. An experimental technology demonstration mission paving the way for space-based interferometry will be launched this year, and pulsar timing observations are placing ever-greater astrophysical constraints on the dense stellar environment around massive black holes. This talk will introduce the concept of using gravitational wave measurements as an astrophysical probe and survey the status and prospects for current and future observations.


Tuesday, 25 August 2015

Plasmonics and Metal Optics for Sensing, Energy Harvesting, and Displays

Speaker: Dr. Junpeng Guo (UAH/ECE)
Location: OPB 234, 2:30pm
Abstract: Metals are high density plasmas with bulk plasma frequencies in the UV range, which makes metals having negative electric permittivity in the wide spectral range from the visible to microwaves. Structured metals, such as holes, particles, patches, are intrinsically plasmonic resonators which can store and dissipate electromagnetic energy at their resonant frequencies. Resonant frequencies of metal nanostructures are controlled by the size and geometry of the structure and sensitive to surface conditions. A variety of biochemical sensors have been demonstrated to utilize the plasmon resonance effect of metallic nanostructures. Many of these surface plasmon resonance sensors rely on optical spectrometers for resonance spectral measurement. In this talk, I will present a new surface plasmon resonance biosensor platform that does not need optical spectrometers. The function of spectral measurement is integrated in the system by using grating-patterned nanostructures. Although nanostructures support plasmon optical resonances, metals are intrinsically light absorbing materials. Metallic nanostructures can be designed to completely absorb light at selective wavelengths. In this talk, I also present several metal nanostructures for perfect light absorption in visible and near-IR spectral range for solar energy harvesting and color display applications.