When massive stars in a galaxy die, they explode and create clouds of gaseous debris. If these clouds of debris break out of the galaxy, they can create galactic winds. The nearby Large Magellanic Cloud (LMC) galaxy is ideal for studying galactic winds as it is oriented face-on and is driving out 85 million Sun’s worth of gas. Using observations from the Hubble Space Telescope, we are studying chemical absorption fingerprints from the light that passes through the LMC’s galactic winds. These chemical fingerprints enable us to assess the physical properties of the winds. We are using the light from 150 young, massive stars in the LMC to probe through the LMC’s galactic winds. In order to determine where the LMC’s disk ends and the winds begin, we utilize the Galactic All-Sky Survey observations to trace the motions of the neutral hydrogen gas. Together, these observations will allow us to measure how fast the winds are moving, how much gas they contain, and their ionization states. Exploring the LMC’s galactic outflows will contribute to our understanding of the relationship between a galaxy’s environment and its evolutionary progression.

The antimicrobial properties of ZnO are well documented. Demonstrated effectiveness against various strains of both Gram-positive and Gram-negative bacteria in addition to being an abundant and inexpensive material leave it well positioned for application as an antibacterial agent. ZnO based antibacterial agents see current usage in biomedical, water treatment, food storage and various other industries. Despite the significant promise and proven application, realization of both novel and efficient, targeted applications is hindered by a lack of understanding in the fundamental mechanisms responsible for the antimicrobial properties of ZnO. In particular the role and nature of components of the local bacterial environment in mediating/hindering these antibacterial interactions. Phosphate-rich environments in particular have been observed to inhibit antimicrobial behavior in ZnO though the manner in which this occurs has not been adequately described. To elucidate the environmental interactions relevant to the antimicrobial action of ZnO we investigated the effects of interactions with both bacteria and the bacterial environments on the physicochemical and optoelectronic properties of the free crystalline surface of ZnO microparticles (MPs). This involves exposing hydrothermally grown ZnO MPs to phosphate-buffered saline (PBS) media both with and without the presence of Newman strain S. aureus bacteria. Changes in the surface electronic structure and charge dynamics due to these exposures are monitored via both time and energy dependent surface photovoltage (SPV) conducted prior to and following biological assays. In doing so we demonstrate significant changes in the characteristic timescales of long-lived processes in the SPV transients after exposure to phosphate-rich environments. Such findings point to significant phosphate adsorption at the free crystalline surface. This is further supported by suppression of oxygen rich defect centers after exposure to PBS media. We also comment on the interaction of bacteria as the presence of S. aureus suppresses this adsorption and influences charge transfer processes at short and intermediate timescales.

Excitation and emission (observation) conditions heavily impact fluorescence measurements. Both observed spectra and intensity decay (fluorescence lifetimes), when incorrectly measured, may lead to incorrect data interpretations. The necessity of using so-called total fluorescence intensity or intensity measured under magic angle (MA) conditions is demonstrated for both steady-state and time-resolved fluorescence measurements. Rhodamine 6G (R6G) in two solvents - ethanol and glycerol have been used in order to demonstrate the general importance of Magic Angle observation.

Star clusters have long been used as chemical and dynamical tracers for our home galaxy, the Milky Way. Many of these clusters are the old, metal poor, and massive objects known as globular clusters. These globular clusters are ideal test-beds for studying stellar evolution, stellar dynamics, and Galactic evolution since all the included stars are born from the same gas cloud. In this work, we combine the positions and motions of stars on the sky, provided by the European Space Agency’s Gaia space telescope, with the high-resolution chemical abundances from the Apache Point Galactic Evolution Experiment (APOGEE) to create a catalog of globular clusters. By only using data from two sources this sample of clusters is less susceptible to systematic offsets induced by combining multiple literature datasets. Overall, our catalog includes nearly half of all known Milky Way globular clusters, and a total of 5000 likely stellar members with APOGEE chemical abundances. We use these data to explore the internal properties of globular clusters as well as the population of the clusters as a whole to paint a picture of what the Milky Way looked like when it was first forming.

Characterizing Galactic sub-structures is crucial to understanding the assembly history and evolution of the Milky Way. To accomplish this, we need to identify and analyze the accreted sub-structures. With ESA Gaia and SDSS-IV/APOGEE, studies have been done to analyze the kinematics and chemical abundances, respectively. However, one challenge that still remains is deriving reliable ages for these sub-structures. We utilize the new relationship between the carbon to nitrogen ratio and stellar age derived by the OCCAM team, which has recently been extended to the metal-poor regime, to probe stars within the sub-structures in the metallicity range -1.2 ≤ [Fe/H] ≤ +0.3 dex. This allows us to determine the ages of a greater number of stars within these sub-structures, which paints a more coherent picture of the original galaxies that have been disrupted to form the Milky Way’s halo. Using the sample of halo sub-structures in Horta et al. (2023), we apply the newly extended calibration to determine ages of stars within these sub-structures and compare them to previous age estimates.