NGC 6822 is a barred irregular galaxy located about 1.6 million light years away in the Sagittarius constellation. We are observationally identifying red supergiants (RSGs) in this galaxy to compare with stellar evolutionary models. Stellar evolutionary theory provides us with the expected quantity of RSG populations. The research conducted will allow for a comparison between observational data to theoretical expectations. Here, we propose a new sample of RSG candidates in NGC 6822 that can be utilized as an observational test of such theory. RSG stars are the coolest of the evolved massive stars and have K and M spectral types and temperatures below 4100 K. Typically, they can be up to a thousand times the radius of the Sun and are therefore highly luminous. To find them in NGC 6822, we first used parallax and proper motion values from the GAIA satellite to filter out foreground stars, before using the NIR color-magnitude diagram to eliminate lower-mass asymptotic giant branch star contaminants. Next we transformed the J and K magnitudes to effective temperatures and luminosities to create an HR diagram (HRD), and selected RSGs based on their position on the HRD. Currently, we are comparing our results to previous spectroscopically confirmed RSGs. In combination with population studies done by ourselves and others in the Local Group galaxies IC 10, M31, M33, and the Magellanic Clouds, we can test model predictions across a wide range of metallicities. Additionally, by locating a population of RSGs in NGC 6822, future possibilities for studying these massive stars with direct spectroscopic follow-up are created.

Lightning is an intensely energetic atmospheric phenomenon that causes significant loss of life and property, ignites wildfires, and sustains the natural cleansing power of the atmosphere. Lightning is also an indicator of storm intensity and of the microphysical properties of cloud precipitate. Thornton et al. (2017) showed that lightning frequency over two of the world’s busiest oceanic shipping lanes is on average double that over neighboring ocean areas. Fuel combustion by ships emits sub-micrometer particles which alter cloud microphysics and possibly storm intensity, providing a potential explanation for the increased lightning density over the shipping lanes. Starting January 2020, the International Maritime Organization imposed a seven-fold reduction in the amount of sulfur in shipping fuel. Fuel sulfur is a significant contributor to particulate matter in ship exhaust. In addition, there was a significant temporary reduction in maritime ship traffic related to economic impacts of COVID-19. We use lightning frequency observations from the World-Wide Lightning Location Network (WWLLN) to analyze how these changes in shipping activity and emissions affect lightning enhancements over major shipping lanes in 2020 compared to the past decade. We find that the lightning enhancements over shipping lanes in 2020 were significantly lower compared to the past decade, with more than 100% reduction in the lightning enhancement, temporarily, as well as sustained, but smaller reductions in over half of the seasonally active months. Together, these changes suggest both the temporary COVID-19 reductions in ship traffic and prolonged reduction in ship exhaust emissions may have significantly altered lightning activity in major oceanic shipping lanes.

The power of climate models are in part derived from their predictive ability. One such prediction is the Time of Emergence (ToE). The ToE is the year in which the year-to-year variability of a given holistic climate variable over a given period, such as 90th percentile maximum temperature, is overtaken by the effects of climate change. The Time of Emergence can help society plan for our climate future by dictating deadlines for levy construction completion or other such necessary climate change ready infrastructure. In the Coupled Model Intercomparison Project Phase 5 (CMIP5) models and data sets, there are both Global Circulation Models (GCM) and Weather Research and Forecasting (WRF) models. In these two classes of climate models, there are different resolution scales and different parameters. GCM models are less local, do not consider smaller scale geographical features, and lack the regional resolution of WRF models. This analysis compares these two model classes through the ToE, determining how each model sees the emergence of climate change in the Pacific Northwest and Southeast China at local and global levels. The differences therein elucidate the predictive accuracy of each model class at small scales and further highlights the phenotypical aspects of each model class.

The circumgalactic medium (CGM) is a massive reservoir of gas surrounding a galaxy in which density and temperature range several orders of magnitude and contains more mass than the galaxy itself–similar to a cloud engulfing the galaxy. The CGM also plays a substantial role in the life of its galaxy as it will govern the accretion of matter for the galaxy to continue star formation. To better learn about the CGM, many astronomers utilize simulations to test theories by comparing their simulation data with observational data. Yet, current simulations struggle to replicate the CGM and its breadth of properties accurately. This project uses the TEMPEST and Patient0 simulations of Milky Way-type galaxies and a novel analysis method–known as synthetic spectroscopy–to better understand the effects of cosmic rays on altering how the CGM gas is ionized and how cooler CGM gas moves within the cloud. Many simulations tend to omit cosmic ray physics, however, cosmic rays are believed to provide non-thermal pressure support which will change the ionization structure of the CGM. Through our use of synthetic spectroscopy, we extracted column density and velocity information of various ions, such as HI and OVI, from our simulation to generate velocity histograms and plots of column density versus distance from the galaxy. Ultimately, this provided us further insight into the impacts of cosmic rays on setting the ionization and kinematic properties of the CGM which will better inform us on galactic evolution.