2019 REU Results
UW–Madison Astrophysics REU Program Summer 2019
Leonardo Clark (University of Minnesota)
A Long Molecular Filament towards Galactic Longitude l=352
Mentor: Audra Hernandez
Using data from the Three-millimeter Ultimate Mopra Milky Way Survey (ThrUMMS) of molecular-line emission — which covered a 2°-thick section of sky along the galactic midplane from l = 360° to l = 300° at several radio frequencies — we have measured the properties of a long Giant Molecular Filament, G352.00+0.65 which lies parallel to the Galactic plane, and is generally presumed to be part of the Sagittarius-Carina spiral arm. At a minimum, this filament is five degrees long, and may extend as long as ~ 13°, making it one of the longest molecular filaments catalogued to date. Three major star forming complexes with Gaia parallax distances lie along this structure: NGC 6357 (l = 353.2°, d = 1.77 ± 0.14 kpc, Nstar = 178), NGC 6334 (l = 351.1°, d = 1.63 ± 0.13 kpc, Nstar = 5), and RCW 120 (l = 348.2°, d = 1.68 ± 0.15 kpc, Nstar = 31). We characterize the mass, structure, and star formation properties of this filament, and note that a section of this filament lies at VLSR > 0. This is unexpected considering that material within the solar circle in this direction should only have negative velocities. This work was supported by the National Science Foundation’s REU program through NSF awards AST-1560016 and AST-1852136.
Sarah Kostmayer (Mississippi State University)
Cataloging Dwarf Galaxies in Abell Galaxy Clusters
Mentor: Ralf Kotulla
Galaxy clusters are gargantuan groupings of many different kinds of galaxies; the intricacies of interaction within these clusters is still something of a mystery. This project stands to examine the structure of three Abell clusters of varying size and distance through the distribution of their dwarf galaxies. A dwarf galaxy is a significantly smaller, less massive galaxy, and despite their size difference, they tend to make up the larger population by number of any cluster. Their small size allows them to more prominently display the effects of cluster tides on their structure (and frequency). By cataloging the number of ultra diffuse galaxies in these clusters, we will be able to learn more about cluster forces and the accuracy of current cluster simulations. The process begins with R band data from the Subaru Hyper Suprime camera, and a combination of Source Extractor and Galfit technologies are used to identify light sources in a given field and catalog the few in a field that were the UDG’s we want by examining their size, magnitude, elongation, and many other characteristics. The results give a view into the intricacies of the galaxy clusters; based on our preliminary results we find a distinctly irregular structure to them and a noticeably lower number of dwarfs relative to the giant population in the center as opposed to the outskirts. This indicates that dwarf galaxies may be destroyed in dense environments. This work was supported by the National Science Foundation’s REU program through NSF awards AST-1560016 and AST-1852136.
Allison Erena (Smith College)
Playing with Matches
Mentor: Eric Wilcots
In this project, we identify candidate AGN from the SDSS eBOSS catalog by comparing position on the sky and redshift of observed QSOs to galaxy groups identified in SDSS DR8 by a modified friends-of-friends algorithm. We aim to identify characteristics of these candidate AGN; in particular we examine typical position in the group, finding that about 30% of our AGN are located in the brightest group galaxy (BGG), 40% are located in another member galaxy, and the remaining 30% did not match to a member galaxy (likely indicating an incomplete group member catalog). We suggest that with such a significant proportion of AGN located outside the BGG, group dynamics may play a greater role in activation of AGN than previously thought.
Emily Geist (Juniata College)
Comparing Galaxy Bar Strengths with Star Formation Rates
Mentor: Jay Gallagher
More than half of all spiral galaxies exhibit a “bar” consisting of dense populations of stars moving on elongated orbits around the galaxy centers. Despite the prominence of bars, the specifics of bar evolution and their role in galactic dynamics and galactic evolution remains abstract. Galactic bars are thought to affect the star formation rates (SFRs) of galaxies by transferring angular momentum to the outer regions of the galaxy which causes gas to flow inward towards the center. Using PanSTARRS data, we measured the bar strength of 40 galaxies using isophote analysis to determine the percentage of stellar mass that resides in each galaxy’s bar. SFRs were determined by measuring the luminosity in the 22-24 micron mid-infrared. We compared these measurements for possible correlations and found a strong correlation does not exist between a galaxy’s SFR and the strength of its bar. However, the data does indicate an average range of bar strength versus SFR with a separate group of star-burst galaxies with strong bars. This work was supported by the National Science Foundation’s REU program through NSF awards AST-1560016 and AST-1852136.
Andrew Toivonen (University of Notre Dame)
Cosmic Ray Energy Spectrum in the Heliosphere
Mentor: Jay Gallagher
There is an anisotropy in the detection of TeV particles incident on our solar system from interstellar space. These particles, known as cosmic rays, consist of mainly protons, helium, and other atomic nuclei and propagate through our solar system by spiraling along magnetic field lines. The heliospheric magnetic field is known to have an effect on the trajectories of cosmic rays, and we are analyzing how this magnetic field affects the trajectories at various energies differently. Using Liouville’s Theorem and time-reversibility, we simulated anti-protons originating from Earth backwards in time. These simulations provided us with regions in the sky that are magnetically connected to Earth’s approximate position in the solar system, from which we then simulated protons forward in time. By measuring the energy spectrum of particles incident on target spheres of various sizes around the Earth, we found that the heliosphere does have an impact on protons in the 1-100 TeV range. A peak in the energy spectrum of our simulations was observed at ~6 TeV, which may be due to the gyroradius of such particles being comparable to the diameter of the heliosphere. This work was supported by the National Science Foundation’s REU program through NSF awards AST-1560016 and AST-1852136.
Ariel Daniel (Northern Arizona University)
Temperature Control for Astrophysical X-ray Detectors
Mentor: Dan McCammon
To better understand how galaxies like our own formed and how they evolve, we must observe not only bright objects like stars, star forming regions, and supernovae, but also the matter that is more difficult to detect. This matter is the diffuse hot gas that is in, around, and between galaxies. X-ray detectors are ideal when trying to investigate these regions of million-degree gas throughout the galactic halo, the interstellar medium, and the circumgalactic medium. These X-ray detectors are used on sounding rocket flights and X-ray satellites, and this instrumentation requires extremely stable temperatures around 0.05 K. The detectors have to be kept in a cryostat where they are kept at a constant temperature of only a few tens of mK for ideal energy measurements of X-ray photons. Detectors are cooled by an adiabatic demagnetization refrigerator, where changing the voltage on the magnet will help regulate temperature, and a thermometer dictates if the magnet should be stronger or weaker. This requires accurately measuring a tiny voltage signal from a thermometer. To do this, an amplifier that adds very little noise to the thermometer signal is required. By creating and editing preamp circuit schematics and then making and testing these boards, a large signal is produced that is easy to read with very little noise. By using these high-resolution X-ray instruments, the state of the hot gas can be accurately detected and characterized. This work was supported by the National Science Foundation’s REU program through NSF awards AST-1560016 and AST-1852136.
Samantha Creech (University of North Carolina, Asheville)
Testing the Efficiency of Wavelength-Shifting Fibers for the Next Generation of Neutrino Telescopes
Mentor: Nahee Park
The low cross section of neutrino interactions requires that high energy neutrino observatories have a large detector covering a volume of space on the order of a cubic kilometer. Modern high energy neutrino observatories, such as IceCube, utilize 3D arrays of photo-detectors embedded in transparent material. The next generation of neutrino detectors will be on the order of ten cubic kilometers, and will be essential to studying astrophysical neutrino sources. In order to improve the sensitivity of this large-scale telescope, it is important to design a detector with increased efficiency at a relatively low cost. The Fiber Optical Module is one proposed design for the next generation of photo-detectors; this module would utilize wavelength shifting optical fibers and would not require a thick glass vessel, thus increasing the module’s efficiency at detecting the ultraviolet and blue light that Cherenkov radiation peaks at. Additionally, a detector of this kind can be relatively inexpensive. This study aims to characterize the efficiency of wavelength shfting fiber at transmitting ultraviolet light in a laboratory setting. We then compare experimental results with a Geant4 Monte-Carlo simulation. We present the preliminary results of this laboratory test..