Senior Theses

Maedline Shepley, 2020

Title: A Cosmic "Where's Waldo?": Star Formation in Low-Mass Dwarf Galaxies

Summary: Throughout this thesis, current work on the final 70 galaxies of SHIELD has been presented. The discussion was begun with the SHIELD project's roots in the ALFALFA survey and how ALFALFA provided the groundwork for SHIELD. This discussion continued with a brief description of the KPNO observatories and the subsequent processing. Detailed descriptions followed of the science image creation via pipeline MES.cl and also of the measurement process that occurred with hadophot, Rgas, and HAgal. Finally, SHIELD_phot_calc, a python code written to derive and plot the physical properties of the SHIELD galaxies, was introduced, and a critical eye was given to the results gathered from the measurement and calculation process. From all this work, it was discovered that 56 our of the 82 SHIELD galaxies hasd Halpha detections and that these galaxies tend to have very small diameters and low luminosities compared to galaxies like our own. It was also discovered that though it seemed that more luminous galaxies tended to have higher SFRs, a range of SFRs (10^-5 to 10^-2 solar masses per year) exists for most absolute magnitudes. Despite this large range of SFRs, all the SHIELD galaxies do share one thing related to SFRs in common: All of their SFRs pale in comparison to the SFR of the Milky Way, which is on the order of about one solar mass per year.

Maria Belen del Valle Coello, 2020

Title: Simulations of neutron-argon recoils in CENNS-10 detector for feasibility of an in-situ quenching factor measurement

Abstract: The CEvNS interaction is a key part of studying supernova events, particularly for understanding the bulk of energy and momentum transport in the moments after stellar collapse. The CENNS-10 detector at Oak Ridge National Lab is one of a suite of detectors searcing for this interaction and providing insight into the physics of these astrophysical events. Further calibration of the CENNS-10 detector is necessary to improve the measurement of CEvNS events. In this work, the interaction of neutrons and liquid argon nuclei is simulated to provide insight into the feasibility of performing an in-situ measurement of the quenching factor for the CENNS-10 detctor, which will be used as a calibration tool to understand the signals of nuclear recoils in the detector.

Bryce Cousins, 2019

Title: Studying the Spectra and Environments of Star-Forming Galaxies

Abstract: Star formation is a ubiquitious process throughout the Universe that governs the evolution of galaxies, but the factors influencing it are not well-understood. To investigate these unknowns, the "Star Formation Across Cosmic Time" (SFACT) Survey was established, and is actively producing data of star-forming emission line galaxies (ELGs) across the Universe. However, the thousands of ELGs discovered with SFACT poses a computational problem since each galaxy's spectrum must be individually processed to obtain its emission line properties. To address this, I present the "WRapped Automated Line Fitting" (WRALF) software package that I developed to process the spectra of star-forming ELGs. WRALF is a spectral analysis program created in Python that automatically processes spectra to provide estimates of emission line properties including redshift, line flux, line ratios, and reddening coefficients. WRALF was applied to two fields of the SFACT survey to measure the spectra of 219 ELGs. I present visualizations of these ELGs admist non-ELGs from the Sloan Digital Sky Survey to provide a qualitative picture of their cosmic environments. I then present quantitative measurements of the environments using a nearest-neighbor analysis. In this preliminary analysis, I find that higher-redshift ELGs tend to posess larger nearest-neighbor distances than both lower-redshift ELGs and non-ELGs at any redshift. These findings are consistent with prior studies that have found ELGs to be in lower-density environments relative to non-ELGs. This research also suggests that the sample of ELGs may contain distinct constituent populations of galaxies which each possess different clustering tendencies. These analyses are actively being performed and improved with the progression of the SFACT survey, where every newly-discovered ELG is processed with WRALF. SFACT and WRALF have led to an extensive, growing dataset of galaxies; this will support the current study of ELG environments, and will enable a range of other applications in extragalactic astronomy in the future.

Joseph Dmitri Elfenbein Watkins, 2019

Title: The KPNO 2.1m Hα Dot Catalog

Summary: This thesis presents the entirety of the work done on the Hα Dot 2.1m catalog from 2017-2019. The Hα Dot project began serendipitously, a spin-off project of the ALFALFA Hα survey (Keller 2008). These isolated, point-sources of emission were spotted in the data taken for the ALFALFA Hα survey, and upon obtaining follow-up spectra of them, it was clear they were individual objects not associated with the target galaxy. This confirmed that Hα Dots were a unique kind of astronomical object that visibly show up in narrow-band imaging. Data for the ALFALFA Hα survey were obtained using the WIYN 0.9m and 2.1m telescope located at Kitt Peak National Observatory (KPNO) in Tucson, Arizona. Separating the data from the 0.9m and 2.1m telescope coalesced into two different databases of Hα Dots, those found in 0.9m images and those found in 2.1m images. There are a total of 358 Hα Dots in the 0.9m database and a total of 454 in the 2.1m database, totaling to 812 new and interesting astronomical objects to be further investigated.

In the 2.1m Hα Dot Catalog, each Hα Dot has valuable information about its position and brightness. It contains the astrometry we derived from our data and the astronometry available in the Sloan Digital Sky Survey (SDSS) Data Release 12 (DR12). It also contains all the line fluxes we obtained from our photometry, as well as SDSS r-band magnitudes. We enclose all this information in the database for the purpose of allowing other astronomers looking to find, measure, or use information about Hα Dots.

As part of a side-project and learning experience, the 0.9m Hα Dot Catalog now includes 18 new, fully-reduced spectra of Hα Dots. These spectra provide us with more information about the physical processes producing strong narrowband emission. These spectral reveal not only Hα-detected Hα Dots, but [OIII]- and [OII]- detected Hα Dots with moderate redshifts. This is consistent with the results of the spectroscopic follow-up of Hα Dots detected in the 0.9m data. All present emission lines in these new spectra were also measured for use in constructing line-flux ratios, for use in determining the ionization mechanism responsible for these emission lines.

Brooke Kimsey-Miller, 2019

Title: A Recipe for Green Pea Environments

Goal of this Project: The Green Peas have an extreme star formation rate, which ranges from 3 to 40 M_sun/year. For comparison, the Milky Way has a SFR between 0.68 - 1.45 M_sun/year, but is over 100 times larger than even the more massive Green Peas. The goal behind this research is to quantitatively describe the galactic environment surrounding the Green Peas in order to decide if merging galaxies could be a driving mechanism in this extreme star formation rate. A distribution of galaxies surrounding Green Peas can be created by obtainign spectroscopic velocities of these neighboring galaxies. The distributions allow for an examination of the large scale structure surrounding the target, as well as provide a stepping stone for a quantitative measurement of galactic density.

Nicholas Barth, 2018

Title: Rotation Signatures in M10 and M71

Abstract: We present a study of the internal kinematics of two globular clusters, M10 and M71, using individual radial velocity (RV) measurements obtained from observations using the Hydra multi-object spectrograph on the WIYN 3.5m telescope. We measured 120 RVs for stars in M10, of which, 107 were determined to be cluster members. In M71, we measured 83 RVs and determined 799 of those measurements belonged to cluster members. Using the cluster members, we determine a mean RV of 75.9 +/- 4.0 (s.d.) km/s and -22.9 +/- 2.2 (s.d.) km/s for M10 and M71, respectively. We combined the Hydra RV measurements with literature samples and performed a line-of-sight rotational analysis on both clusters. Our analysis has not revealed a statistically significant rotation in any of these two clusters with the exception of the inner region (10"-117") of M10 for which we find hits of a possibly significant rotation with amplitude equal to 1.13 +/- 0.18 km/s and a rotational axis at a position angle of 205 +/- 34 degrees. We also explored the rotation of the multiple stellar populations identified in M10 and M71 and found no statistically significant difference between their rotational properties.

Neil Bassett, 2018

Title: Constraints in Internal Stellar Physics from Lithium in NGC 752

Abstract: Observations taken with the Hydra multi-object spectrograph on the WIYN 3.5m telescope were used to study the lithium abundances of main sequence stars in the open cluster NGC 752. High precision UBVRI photometry from the WIYN 0.9m provided updated 10-color based effective temperatures for all but the brightest cluster members. The Li morphology of the cluster was studied by selecting proper motion and radial velocity cluster members consistent with the single star fiducial main sequence with small sigma(Teff) (<75K).

The results confirm that the Li morphology of the cluster displays several striking departures from the predictions of the standard model of stellar evolution. The highly non-standard Li dip in F dwarfs is observed in NGC 752. A second group of depleted stars at temperatures hotter than the Li dip is also observed. Comparison with the younger clusters Praesepe and the Hyades shows that Li depletion continues during the main sequence, contrary to the predictions of standard theory.

Tyler Jones, 2018

Title: Evaluating the Basic Parameters of the Open Cluster NGC 1817 Using UVBRI HDI Photometry

Abstract: This honors thesis presents the results of a study conducted of the open star cluster NGC 1817 using UVBRI photometry taken with the Half Degree Imager (HDI) at the WIYN 0.9m telescope at Kitt Peak National Observatory. We determined the cluster parameters: reddening, metallicity, distance, and age. Using Color-Color diagrams we calculated a reddening of E(B-V)=0.25 \B1 0.01 and a metallicity of [Fe/H]=-0.40 \B1 0.10. Using color-magnitude diagrams (CMDs) we calculated a distance of 1485 \B1 55 parsecs and an age of 1.21 billion years \B1 0.027 billion years (with possible additional systematic errors).

Tasman Payne, 2018

Title: Stellar Populations of Nearby Galaxies: Colors and Radial Trends

Abstract: A survey of 32 nearby low-mass galaxies was processed and analyzed to attempt to find trends in the color and star formation rates indicative of various galaxy formation theories. What was found was that, in general, there were no color trends and the star formation rate radial profiles seemed to be independent of the color gradients.

William Bowman, 2016

Title: Detecting Multiple Populations in Globular Clusters

Abstract: We present g´ and intermediate waveband photometry of the blue CN-band in stars in the globular clusters M3, M13 and M71 taken with the WIYN 0.9-m telescope. CN band strengths are correlated with measured sodium abundances to establish whether the CN band can be used to discriminate multiple stellar populations in globular clusters. This project seeks to develop methods of detecting popula\AD tion gradients in integrated cluster light, which can then be applied to globular clusters in other local group galaxies.

Andrew Nine, 2016

Title: A UBVRI Photometric Analysis of Open Cluster NGC 2423

Abstract: This honors thesis presents the results of a precision photometric analysis of the open cluster NGC 2423. The data for this analysis were acquired on the WIYN 0.9-meter telescope at Kitt Peak National Observatory, and were analyzed to determine the parameters of age, metallicity, distance, and reddening. Using the color-color diagrams, we determined the metallicity to be [Fe/H] = -0.19 \B1 0.02 and the reddening to be E(B-V) = 0.108 \B1 0.005. We then compared the color-magnitude diagrams to the Yale-Yonsei isochrones to determine the cluster age to be 1200 \B1 100 Myr and the distance to be 977 \B1 37 pc. (There may be additional systematic errors.) The work performed for this study also provides data for use in future photometric and spectroscopic studies.

Timothy Braun, 2015

Title: Detection of an Extended Outflow in NGC 4102

Abstract: We report the detection of an extended galactic outflow in narrowband Hα imaging of NGC 4102, a nearby SABsb spiral galaxy that hosts a low-ionization nuclear emission-line region (LINER) and a circumnuclear HII region. NGC 4102 is a moderate luminosity galaxy (M_B = -19.3) in the Ursa Major Cluster. The ionized gas outflow protrudes out to 60" (5 kpc at an adopted distance of 17.4 Mpc) to the northwest of the galactic center and may extend as much as 75" (6.3 kpc). Follow-up integral-field spectroscopic observations reveal split line profiles over the outflow region, indicative of both blue- and red-shifted emission-line components where one spectrum shoes emission-lines split approximately 150 km/s. Based on [NII]/Hα and [SII] flux ratios of this region, the line emission appears to be non-thermal and originating from a low density environment. By supplementing this work with the literature, we hypothesize that this outflow originated from a nascent nuclear starburst region, while any supporting wind from the AGN in the past is ambiguous.

Christian Hayes, 2015

Title: A BVI Photometric Study of the Old Open Cluster Czernik 30

Abstract: We present the first BVI photometry of the old open cluster Czernik 30, a distant cluster, subject to high field contamination. In order to account for the field contamination, we employ a statistical field star subtraction method to clean the produced color-magnitude diagram, clearly revealing the cluster sequence. Applying theoretical isochrones from a number of different models, we determine properties which are consistent between the individual models and with the previous study of this cluster. Our best fit model determines the following properties of Czernik 30: age = 2.8 +/- 0.3 Gyr, [Fe/H] = -0.2 +/- 0.2, (m-M)_V = 14.8 +/- 0.1, E(B-V) = 0.24 +/- 0.06, and E(V-I) = 0.36 +/- 0.4. This shows that Czernik 30 is an old sub-solar metallicity cluster located at a galactocentric radius of about R_gc ~ 13.3 kpc. Thus, Czernik 30 provides an interesting target for future observations, given that it is one of a small number of known old open clusters and of clusters in the outer disk of the Galaxy. Additionally, given its location in the Galaxy, Czernik 30 falls around the bend or transition of the metallicity gradient seen in open clusters.

Aaron Monk, 2015

Title: A UBVRI Analysis of Open Cluster NGC 2539

Abstract: This honors thesis presents the results of a high-precision UBVRI photometric study of the open star cluster NGC 2539. Data were acquired on the WIYN 0.9m telescope at Kitt Peak National Observatory and analyzed to determine the star cluster parameters of age, metallicity, reddening, and distance. From color-color diagrams, we determined a reddening of E(B-V) = 0.080 +/- 0.005 and a metallicity of [Fe/H] = +0.03 +/- 0.05. We compared color-magnitude diagrams to Yale-Yonsei isochrones and derived a distance of 1515 +/- 50 parsecs and an age of 580 +/- 15 million years. Additionally, this work has provided a high-precision data set that can be used in future studies.

Daniel Wavle, 2015

Title: A Kinematic Analysis of Nine Low Mass Gas-Rich Galaxies

Abstract: We present results from a kinematic study of the neutral hydrogen in nine dwarf irregular galaxies. Six of the galaxies in the sample exhibit extended hydrogen envelopes, providing a useful tracer of structure out to many disk scale lengths. We combine archival HI data from the Very Large Array with optical data from the WIYN 0.9m telescope to model and decompose the galaxy rotation curves into baryonic and dark matter mass components. No correlation was observed between the size or structure of the dark matter halos and extended hydrogen structure, and we show that all of the dwarfs appear roughly similar in the context of the gravitational potential of dark matter. We therefore provide an analysis of the stability of the gaseous disks using a criterion presented by Toomre (1964) and show that all these dwarf galaxies are stable against star formation throughout their disks, explaining in part the apparent inefficiency of star formation in the hydrogen envelopes.