Stellar Population Synthesis and Photoionization Models

Using the latest generations of the Starburst99 stellar population synthesis models and the Mappings III photoionization code, we have recently generated a new grid of model spectra for star-forming galaxies (available for download here). We are currently in the process of updating these models using the new Geneva evolutionary tracks with rotation. We hope to eventually use these models to develop and/or recalibrate a number of rest-frame optical and UV ISM diagnostics, utilizing them to probe the ISM properties, stellar populations, and star formation histories of both nearby and high-z galaxies.

Gamma-Ray Burst and Supernova Host Galaxies

This research is aimed at exploring the host environments that produce the young massive progenitors of long-duration gamma-ray bursts (LGRBs) and core-collapse supernovae (CCSNe). As a continuation of research begun during my PhD thesis, we are conducting the first uniform high-quality spectral survey of LGRB host galaxies, using the Keck telescopes on Mauna Kea, the Magellan telescopes at Las Campanas, and the Gemini telescopes at Mauna Kea and Cerro Pachon. These observations allow us to characterize many properties of these galaxies’ ISM environments, placing them in context by comparing them to data from a number of existing star-forming galaxy surveys. We can also apply these same diagnostics, along with the latest generation of stellar population synthesis and photoionization codes (now available here!), to the host galaxies of nearby sub-luminous LGRBs and core-collapse supernovae. We’re currently continuing our LGRB host work with ongoing observations at places like Keck and Gemini, and beginning some new work on CCSNe host galaxies using the 3.5-meter telescope at Apache Point Observatory.

Physical Properties and Heavy Element Abundances in Red Supergiants

Red supergiants are a helium-burning phase in the evolution of massive stars that until recently was poorly understood and reproduced by the predictions of stellar evolutionary models. Our previous research has aimed at making the first accurate determinations of these stars’ physical properties in the Milky Way and nearby Local Group galaxies (the Magellanic Clouds, M31), utilizing moderate-resolution spectrophotometry and the latest generation of the MARCS stellar atmosphere models. We are currently extending this research to other low-metallicity Local Group galaxies (NGC 6822, WLM) and acquiring high-resolution spectroscopy of previously-observed RSGs in our sample using the Apache Point Observatory 3.5-meter telescope and the Magellan telescopes at Las Campanas Observatory. With these data and synthetic stellar spectra, we can construct the first detailed abundance profile for RSGs, providing a valuable test of the MARCS stellar atmosphere models.