Astrophysics Parallel Talks

The process of how massive, quiescent, elliptical galaxies evolve to their present day status is one of the biggest questions in extragalactic astronomy. As these galaxies stop forming stars they also transform from extended disks to compact ellipticals, but a mechanism responsible for both changes remains undiscovered. Previous studies with the Hubble Space Telescope have found a potential transition population to help fill the gap: massive, compact, star-forming galaxies dubbed ‘red nuggets. In this work, we take a second look at this population using new JWST data which grants us access to redder wavelengths. Through the eyes of JWST, we find many of these candidates are actually less massive, already quiescent, or more extended than previously understood. These results suggest that the red nugget population is not as common as once thought, and therefore cannot fully explain how today’s quiescent galaxies came to be.

When a supermassive black hole is violently ejected from its host galaxy's center, it can drag along a cluster of stars that were gravitationally bound to it, forming a compact, glowing "entourage" that travels with it through space. Two very different processes can cause this ejection: gravitational-wave recoil, where the merger of two black holes sends the resulting black hole rocketing off in one direction, and three-body slingshot interactions, where a black hole is flung out through gravitational encounters with other massive objects. Recent discovery of a candidate runaway supermassive black hole moving at nearly 1,000 km/s has renewed interest in figuring out how to tell these two origin stories apart. Our research asks whether the amount of stellar material left bound to the black hole differs depending on which mechanism ejected it. For the gravitational-wave case, we derived a mathematical formula predicting how many stars stay bound as a function of ejection speed, and confirmed it against computer simulations of stars orbiting a recoiling black hole. For the slingshot case, we ran direct N-body simulations using the REBOUND code, tracking how much stellar mass remains bound as the black hole is flung away from its interaction partners. We find that the two mechanisms leave behind noticeably different amounts of bound stellar mass, meaning that observing the stars and light around a runaway black hole could reveal how it was ejected in the first place.

I am investigating the physical behavior of downflows within bright solar granules on the Sun's photosphere. These downflows are commonly referred to as Dark Dots, due to their appearance. Dark Dots form within the interiors of solar granules before evolving and merging with the surrounding granular lanes. My data consist of a time series of solar granulation images captured by the DKIST telescope using the Visible Broadband Imager. This instrument provides high-contrast images of the photosphere using a G-band wavelength filter of around 430 nm. I am working with intensity-based data to collect measurements of the trajectories, velocities, diameters, intensities, lifetimes, and spatial distributions of the Dark Dots while also exploring the shape and evolution of the solar granules themselves. I have developed a number of algorithms in order to obtain these measurements. The most challenging tasks have been determining precisely when a Dark Dot first emerges within a solar granule and when it merges into a granular lane, at which point it is no longer distinguishable by its intensity. The ability to do this is essential to capturing a complete data set and gaining a better understanding of these objects’ dynamics.

The Mukhanov-Sasaki (MS) equation governs the evolution of primordial scalar perturbations during inflation, encoding the quantum-to-classical transition responsible for the large-scale structure of the universe. We present a formally exact optical analogue of the MS equation in the de Sitter limit, realized through a gradient-index (GRIN) medium with a constructed refractive index profile n(z) that maps the cosmological horizon crossing onto an optical turning point where n(z*) = 0. The comoving wavenumber k emerges naturally from the paraxial approximation as k = k⊥²/2k₀, establishing a rigorous correspondence between beam envelope dynamics and inflationary mode evolution. Numerical solutions of both systems, initialized with Bunch-Davies vacuum boundary conditions, are evolved through horizon crossing and exhibit exact amplitude agreement across all scales, confirming the analogy is not merely qualitative but mathematically precise. The refractive index vanishes at the horizon, producing mode freezing in direct analogy with wave evanescence at an optical turning point. This construction provides both a computational validation framework for MS equation solutions and a physically intuitive realization of inflationary dynamics, with potential applications in analogue gravity laboratory experiments.

The Dark Energy Spectroscopic Instrument (DESI) is one of the largest high-resolution 3D map of the Universe to date. DESI’s scientific success also creates an operational challenge. The instrument is extremely complex; it relies on a large and constantly growing collection of technical documentation for telescope and instrument operations. During observing, operators often need to quickly find procedures, known issues, and troubleshooting information across manuals, technical notes, and operational records. This research focuses on the development of AskDESI, a fully local AI expert system for retrieving and summarizing DESI operational knowledge, designed to work without cloud-based services. The project uses a Retrieval-Augmented Generation (RAG) pipeline to extract text from technical documents, divide it into searchable sections, store vector embeddings, and retrieve relevant information from natural-language questions. Testing shows that retrieval structure strongly affects system performance. Section-aware and graph-assisted retrieval produced more complete answers, improved source traceability, and reduced failures caused by fragmented document context. AskDESI is also designed to refuse unsupported questions and use validated expert corrections instead of generating unverified operational procedures. The system provides a foundation for future testing in operational shadow mode.

Dust-obscured galaxies provide a unique opportunity to study galaxy evolution during periods of intense star formation and represent the most extreme examples of processes occurring in the broader galaxy population. Determining whether these galaxies host active galactic nuclei (AGN) is challenging because dust attenuation can mask conventional AGN signatures, yet identifying AGN is essential for understanding galaxy evolution, as well as for accurately interpreting galaxy properties. We use the James Webb Space Telescope (JWST) to analyze emission-line diagnostics in the near-infrared spectra for a sample of dust-obscured galaxies, and combine these measurements with independent X-ray AGN tracers to characterize the contributions of AGN and star formation to the observed emission. Using these tracers, we assess the AGN occupation fraction in dust-obscured galaxies and evaluate the utility of near-infrared emission-line diagnostics for identifying AGN in dust-obscured galaxies. Our results indicate that star formation dominates the observed emission in most of our sample, while also demonstrating that near-infrared emission-line diagnostics are a powerful tool for identifying AGN where dust obscuration limits conventional optical diagnostics. These findings highlight the importance of combining multiwavelength observations to confidently identify AGN and improve our understanding of galaxy evolution in heavily obscured systems.

Open clusters are groups of stars that formed together from the same cloud of gas, making them natural laboratories for testing how stars evolve. By measuring the brightness and color of member stars and plotting them on a Color-Magnitude Diagram (CMD), astronomers can extract a cluster’s distance, age, composition, and other properties. Messier 29 sits behind lots of galactic dust, which means its reddening is significant and its properties, therefore, uncertain. Using Sonoma State University’s Gamma Ray Optical Robotic Telescope (GORT) to collect photometry in Blue, Visual, Red, and Infrared, I fit theoretical isochrones to the CMD of the open cluster Messier 29 to solve for its physical properties. This work was funded by Sonoma State University and NASA. I determined a distance of 5,240 light years, an age of roughly 20 million years (10^7.3 years), a metallicity of Z = 0.014 (1.4%), a reddening of Av = 3.24, and a stellar mass range of 0.748–11.2 solar masses. These results confirm and extend existing characterizations of M29 from the Gaia space telescope and demonstrate the power of photometric methods for studying young open clusters.

Determining stellar parameters have long been of interest to astronomers. One way of determining these parameters is using asteroseismology, the study of sound waves in stars. The pressure and gravity waves in the convective layers provide us very precise measurements of certain stellar parameters. However, studies involving galactic bulge stars have been limited, given the heavy dust extinction in the bulge. The upcoming launch of the ROMAN telescope and start of the ROMAN Galactic Bulge Time Domain Survey (GBTDS) offers a great opportunity to study this area. To prepare for this, we built a list of asteroseismic targets for the upcoming mission. We combined photometry from VVV and 2MASS, which we used to isolate red giant stars. Crossmatching this data with Gaia parallaxes, we were able to constrain red giants within the bulge. We find over 500,000 potential targets within the bulge, compared to previous estimates of about 300,000. This list of targets can be used as a starting point for asteroseismic studies after the ROMAN launch.