Fall 2017 Physics Colloquium

Thursday, September 14th
New Physics Majors Induction Ceremony

Noon
Tome 115
Lunch provided

Thursday, September 21st
Dr. David Schaffner, Bryn Mawr College

"Heliospheric-Relevant Plasma Turbulence in the Laboratory"

The heliosphere is an extremely rich laboratory for the study of plasma turbulence. However, its exploration is restricted by the limitations associated with remote observation and direct measurements through satellites. In this talk, I will discuss a different approach to the examination of heliospherically-relevant turbulence using a laboratory-based plasma experiment. With a specialized plasma source, magnetically dynamic plasma can be produced in a wind-tunnel-like environment which can mimic certain aspects of astrophysical magnetohydrodynamic (MHD) turbulence. I will explain the conditions through which this type of plasma can be created and then give an overview of the myriad of statistical techniques we use to understand this plasma’s turbulence characteristics. Using these metrics, we can compare the laboratory plasma to various regions of the heliosphere, including the solar wind and the magnetosheath. By utilizing the controlled conditions of the plasma in the laboratory, we can complement results from space physics and computer simulation analyses to generate a more comprehensive picture of heliospheric turbulence.

Noon
Tome 115
Lunch provided

Thursday, November 2nd
Chris Johnson, STScI, Post Doctoral Research Fellow

"Crowded Field Photometry Using Image Subtraction and PSF Fitting: Frmo the Galactic Bulge to Massive Open Clusters"

Crowded field photometry is vital when analyzing dense stellar regions of space that contain thousands up to tens of millions of stars per square degree. Aperture photometry fails in these dense regions since stellar neighbors can be so close that they contribute unwanted light in to your aperture and give false magnitudes. Stars appear as point sources of light when imaged with a telescope and their light can be modeled as a Gaussian function. The light spreads out radially from the bright center (much like a bell curve) and we refer to this function as a "Point Spread Function" or PSF. We can then fit a basic PSF model to all the stars in the field, build up a better average PSF model by iterating through the image and rejecting bad pixels, variable stars, bad images, etc. and create a final master PSF. We then subtract this master from each individual star in each image again and the residuals left behind will tell us something about the source. I have extended the techniques that I used from graduate school to look at X-ray binaries in the Galactic Bulge to uncovering eclipsing binary populations in very young open clusters.

Noon
Tome 115
Lunch provided

Tuesday, November 14th
Sigma Pi Sigma

4:30pm (Speaker & Induction Ceremony)
Tome 115
6:00 pm (Dinner)
Social Hall West

Monday, November 27th
Physics Senior Research Presentations

4:30pm
Tome 115
Refreshments provided

Tuesday, November 28th
Physics Senior Reserach Presentations

Noon
Stafford Lecture Room
Lunch provided

Thursday, November 30th
Physics Senior Research Presentations

Noon
Tome 115
Lunch provided