The ΛCDM model predicts more faint stellar companions than we observe, a discrepancy known as the Missing Satellites Problem. M81, a nearby spiral galaxy at ~3.61 Mpc, provides an opportunity to search for ultra-faint stellar systems beyond the Local Group. Using high-resolution HST data from the GHOSTS survey (de Jong et al. 2006), we identified two young stellar systems in Field 8. Their compact size, morphology, and color suggest they may be previously unknown clusters or extremely faint stellar populations in M81's outer halo.

A new method for recovering the properties of bars has been developed and tested using edge-on-orientated n-body representations of barred disk galaxies. We aim to test this method with near-face-on oriented barred disk galaxies. This process involves inferring a 3-dimensional mass distribution from a 2-dimensional surface brightness image. The recovered 3D mass distribution is then used to obtain the gravitational potential of the barred system. We use this gravitational potential to construct orbits of 20,000 stars within the system. Each orbit is superposed with different weights to best-fit the 2D surface brightness image and 2D Integral Field Spectroscopic data. We construct mock data from 20 co-rotated snapshots from an n-body simulation of a barred disk galaxy with a moderately weak bar to test whether increasing signal-to-noise ratio improves supermassive black hole mass recovery. Following these tests, we will apply this method to the barred spiral galaxy, NGC 4151 using data from both Gemini NIFS and SAURON IFU spectrographs.

XO-3b is a large transiting hot Jupiter on an eccentric and inclined orbit. Its eccentricity causes variable stellar irradiation, leading to a varying temperature; a complicated and possibly asymmetrical temperature structure is hypothesized to exist on the planet. Previous transit observations of XO-3b in the NUV showed an Rp/Rs significantly larger than the optical, indicating the presence of ionized iron past the optical radius of the planet. This suggests that there may be ongoing atmospheric evaporation. However, models suggest that the planet is too massive for significant photoevaporative mass loss. Thus, more investigation of XO-3b is needed to explain its deep NUV transit. Other proposed explanations of the large radius are the presence of silicate clouds, though the expected temperature of the planet fluctuates in and out of the range where silicate clouds could form; or that the planet is burning deuterium, leading to a puffed up atmosphere. The ephemeris of the transit has also been found to be inconsistent in some studies, suggesting that the orbit may be actively circularizing due to tidal dissipation; however, this claim is controversial. In this study, we detect and analyze the transit of XO-3b in both optical and NUV, using a joint analysis of TESS and ISAS data and a NUV XMM-Newton Optical Monitor observation, in order to determine the transit timing and apparent radius differences between optical and NUV.

Barred galaxies can form boxy/peanut or X-shapes (BP/X) due to the bar bending out of the disk midplane. We parametrize the BP/X structure observed in edge-on barred galaxies into radius from the peak of the peanut to the center of the galaxy, width from the center of the peak, and amplitude from the galaxy plane to the peak, bar amplitude (length of the bar), and bar pattern speed. We use a set of N-body models and show that there is a statistically significant correlation between radius of the peanut and bar amplitude, and radius of the peanut and bar pattern speed, indicating a link between X-shape and bar parameters with their relationship culminating in the morphology of a barred galaxy.

Over the past few decades, astronomers have used large-scale simulations and observations to investigate how galaxies form and evolve. A key part of this work involves studying the low-density intergalactic and circumgalactic medium—gas that feeds into galaxies and sustains star formation by replenishing the interstellar medium. One of the most effective ways to probe these regions is by analyzing how they absorb light from bright background sources like quasars.

This project focuses on intervening gas clouds known as Lyman Limit Systems (LLSs), which are optically thick (τ = 1) to hydrogen-ionizing photons at the Lyman limit (rest-frame 912 Å). We analyzed the spectra of ~60 LLSs to investigate their chemical composition and physical properties by measuring redshifts and identifying the Lyman limit break in each system. Using Python and libraries such as AstroPy and Matplotlib, we developed tools for spectral analysis and visualization.

During this analysis, we serendipitously identified a proximate MgII absorber, located near the background quasar, offering a rare opportunity to measure its HI column density. We characterized this absorber by measuring the equivalent widths of MgII and OIII absorption lines, as well as the HI column density. Because proximate MgII absorbers are linked with quasar-driven outflows, this system presents a valuable case study for understanding feedback in galaxy formation. Ongoing work includes comparing this absorber to other proximate MgII systems at similar redshifts to explore their broader role in shaping the intergalactic medium and informing solutions to the overcooling problem in galaxy formation models.

Planetary nebulae (PNe) form towards the final phase in the life cycle of low-to-intermediate-mass stars. Mass lost during the asymptotic giant branch phase is shaped into shells by a fast wind that also causes a shocked inner region called a hot bubble. The role of binarity in the formation of PNe is a growing concern and hard X-ray emission sources have revealed unseen companions. The formation of PNe in globular clusters (GCs) is rare since the stars in GCs are old and metal-poor, and the radiation environment can be destructive for circumstellar material. Hence, the PNe K648 in the GC M15 offers a unique opportunity to study this phenomenon in an extreme environment. Over 100ks of serendipitous Chandra X-ray observations were studied to determine the nature of X-ray emission from K648 first identified as a potential X-ray source by Hannikainen et al. 2005. To pinpoint the nature of the X-ray emission, we carefully aligned the X-ray observations with each other based on the limited number of field sources. Based on this alignment, we conclude that the X-ray emission is very likely diffuse. Next, we compared the X-ray sources with multiple optical and infrared source catalogs to identify a robust alignment that could be used to bootstrap alignments across numerous multiwavelength images. We were able to reduce the uncertainty of the alignment to a quarter of an arcsecond. Based on this alignment, we conclude that the diffuse X-ray emission is most likely associated with the northern arc of the nebula, thus likely resulting from shock interactions rather than binary interactions at the core. This confirmation of the nature of the X-ray emission means that K648 is the most distant source of diffuse X-ray emission detected from a PNe.

The metal oxides titanium oxide (TiO) and vanadium oxide (VO) have long been hypothesized as drivers of temperature inversion in hot Jupiter atmospheres. However, low spectral resolution observations from ground- and space-based telescopes in the pre-JWST era have produced conflicting results on the presence of TiO and VO across the hot Jupiter population. The ultra-hot Jupiter WASP-121b (~ 2500 K) is sufficiently hot that TiO and VO should exist in the gas phase at its day-night terminator, but precise metal oxide abundance measurements proved elusive from the limited spectral resolution of HST.   

Here, we present JWST/NIRISS transmission spectra of WASP-121b, obtained as part of GTO Program 1201. Our retrieval analysis establishes conclusive detections of TiO and VO with ultra-precise abundances (< 0.2 dex). Additionally, we present evidence of stellar contamination, thermal dissociation, and the presence of H2O and H-, offering constraints on the atmospheric metallicity and ionic chemistry in the atmosphere of this enigmatic hot Jupiter.

Photoionization fronts are waves of high-energy photons which ionize the medium through which they are traveling, turning the medium into plasma. Photoionization fronts are present in various high-energy astrophysical phenomena, including supernovae, early universe cosmology, and high-energy-density physics. Recent advancements in laboratory photoionization front experiments provide new opportunities to study the dynamics and interactions of the resulting plasmas, offering valuable insights for interpreting astronomical observations and modeling the thermal and ionization structures of astrophysical environments. Due to experimental limitations in capturing complete measurements, we also employ simulations to study the behavior of photoionization fronts and the plasmas they generate and give more context to our experimental data. We analyze the evolution of argon’s spectral opacity features and relative population in time-dependent simulations, as well as their temperature dependence in steady-state simulations. We also place a notable emphasis on the components of the opacity spectra due to neon-like argon, as it is an ion that has high ground state fractions during the plasma temperature ranges relevant to our experiments. Additionally, we aim to identify general spectral opacity features with temperature sensitivity that can be detected within the resolution limits of available experimental sensors.

I present flux and luminosity measurements of two newly discovered Type Ib supernovae using Swift Ultraviolet/Optical Telescope (UVOT). Supernovae are explosions of stars. The flux is measured in different bands (UVM2, UVW1, UVW2, B, U, and V bands), and the luminosity is measured by flux and distance which is estimated by redshift. Type Ib supernovae are characterized by the absence of Hydrogen lines and the rich in Helium lines and are caused by the core collapsed of massive stars. Calcium-rich Type Ib supernovae share the similar features but show a stronger Ca II line, lower peak luminosity, and fast light curve evolution. In this study, we present observations and analysis of two recent events: SN2025aft, a type Ib SN,, and SN2025coe, a Ca-rich SN Ib. 

Dark matter (DM) halos in Λ Cold Dark Matter cosmological simulations are triaxial, the majority of which exhibit figure rotation (tumbling). Ash & Valluri (2023) found 82 % of TNG50 halos with baryons exhibit figure rotation that is aligned with the minor axis in 62% and with the major axis or no axis in 38% of those halos. We study a subset of 23 halos with stellar disks over the past ∼4 Gyr to understand how a triaxial halo’s motion and orientation can affect the warp of the disk. We measure the warp amplitude at twice the stellar half-mass-radius of disks by decomposing the z-height of the disk density in a number of annuli into azimuthal harmonics. By calculating this amplitude across snapshots spanning a lookback time of ∼4 Gyr and normalizing the measurement by dividing a disk’s warp amplitude with its stellar half-mass-radius, we can track and compare the ”warpiness” of disks across time. The evolution of this warpiness is compared with the tilt of the disk’s angular momentum axis from the halo major or minor axis. Additionally, we plot the orientations of the disk spin axis and halo major/minor axes over time in an orthographic projection to visually confirm precession and figure rotation. By isolating four archetypal galaxies exhibiting varying degrees of halo tilt, disk precession, and figure rotation, we show how these processes form a complex interplay of dynamical forces that can warp disks.

NGC 1275 is a galaxy in the Perseus cluster with a highly energetic nucleus that emits most visibly in the X-ray band. Numerous phenomena have been observed around NGC 1275, but astrophysicists have struggled to study the system due to interference from other objects in the cluster. The X-ray emissions of NGC 1275 are most notable for their significant disruption of the cluster in NGC 1275’s surrounding area. Despite this visual evidence of the power of this X-ray source, emissions from the nucleus of NGC 1275 are entangled with emissions from the Perseus cluster, making precise flux readings elusive. This project aims to develop a method to isolate the emissions from the nucleus of NGC 1275 from contamination caused by other objects in the cluster. X-ray observations of NGC 1275 taken by NASA’s Neil Gehrels Swift Observatory from 2005 until 2025 were graphed and analyzed using Goddard Flight Center’s Xspec software suite. Python and Linux Shell script were developed to sort, bin, and process the 89 relevant observations using Xspec. Xspec was used to calculate key parameters such as the power-law index, normalization, flux, and error range for each source. All parameters except the power-law were linked across observations; importantly, the power-law index was allowed to vary by observation. The power-law index created by the 89 observations excludes individual variations from the cluster, so the flux measurements taken from the power-law accurately reflect the emissions from the nucleus of NGC 1275, not the surrounding cluster. This analysis will provide missing information about NGC 1275, and develop a technique for studying objects in systems with heavy contamination from other sources. Additionally, these results will help refine models of clusters near supermassive black holes.

When multiple galaxies collide, the supermassive black holes (SMBHs) at their centers couple to form a massive black hole binary (MBHB) and scatter stars in the newly formed nucleus before merging. Thus, MBHBs could produce a noticeable deficit of stellar mass and luminosity in the galactic center. In our research, we analyze the surface brightness (SB) profiles of Early-Type Galaxies (ETGs) within 500 million lightyears of Earth to detect such deficits. We sourced images of the ETG sample population from archival exposures captured by the Hubble Space Telescope and used the Fortran-based software Xvista to clean and analyze them. This program produces profiles (plots of surface brightness relative to distance from the galactic center) of an ETG using non-parametric elliptical isophote fitting. The steepness of the inner slope of these profiles indicates whether or not these galaxies have a mass deficit in their core. ‘Core’ profiles have curves with a very shallow inner slope and can indicate a mass deficit in the ETG core. On the contrary, ‘Power-law” profiles have curves with steeper inner slopes and are expected for undisturbed ETGs. I have produced SB profiles for NGC 2300, NGC 3309, NGC 3640, NGC 2768, NGC 3412, and NGC 1389. When plotted, the morphology of NGC 2300 and NGC 3309’s SB profiles best match ‘core’ profiles, NGC 1389 and NGC 3412’s SB profiles best match ‘power-law’ profiles, and NGC 3640’s profile had an intermediate morphology. I failed to fit an adequate SB profile to NGC 2768 due to noise produced by dust within the galaxy. In conclusion, the SB profiles ETGs NGC 2300, NGC 3309, and NGC 3640 should be refined to quantify their inner slopes and mass deficits. Since MBHBs produce gravitational waves during their inspiraling and coalescence, analysis of these ETGs would increase the sample size of galaxies NANOgrav can use to model the gravitational wave background.

With the launch of Roman’s Coronagraphic Instrument, exoplanet imaging can enter the realm of reflected light. This can be particularly useful in exoring detection, as exorings often outshine planets in the visible and near infrared. By revisiting earlier theoretical frameworks, we can model reflected light phase curves of ringless and ringed planets. We can then identify which features in phase curves are characteristic of a ring. Specifically, a ringed planet can appear up to one-hundred times brighter than its planet and can present four extrema within a phase curve instead of two. These attributes can allow us to differentiate between a large, ringless planet and a smaller, ringed planet. Additionally, we can simulate Roman observations, demonstrating how possible these detections will be.

The majority of iron (Fe) enters the interstellar medium (ISM) in the gas phase via Type Ia supernovae, but observational studies suggest that 90 - 99% of ISM Fe is instead present in solid dust grains or nanoparticles. The properties of these grains, which are not well understood, can be probed using X-Ray spectroscopy. The composition of Fe-bearing dust grains are commonly studied by modeling their photoabsorption features. We aim to check the accuracy of three specific models by examining their Fe L shell (n = 2) profiles. Each model contains unique grain sizes, shapes, and compositions, which we replicate with General Geometry Anomalous Diffraction Theory (GGADT) and a Mie scattering subroutine. They are fit using PyXSPEC to high resolution observations of Galactic X-ray binaries from the Chandra X-Ray Observatory and XMM Newton. We report that models containing aligned, oblate-spheroidal dust grains with effective radii  300 nm fit inadequately to observations. Models restricted to 10 to 250 nm spherical grains fit with greater accuracy, reducing the fit statistic by up to 66%, but still perform poorly. Fully understanding the chemical composition of ISM Fe may require more complex parameters, such as porosity and density, in addition to studying silicates bearing Fe nanoparticles.

A population of compact, red active galactic nuclei (AGN) known as “Little Red Dots” (LRDs) has been revealed by the James Webb Space Telescope (JWST), creating a new mystery for extragalactic astronomy. Theorized to be powered by supermassive black holes and corresponding to intense star formation in their host galaxies, we are interested in investigating the LRDs’ formation and whether their characteristics align with or challenge current understandings of AGN. Using observations from JWST’s Near-Infrared Spectrograph through the GO2028 program, we perform a detailed spectral analysis of the LRDs using a data reduction technique that combines the JWST Science Calibration Pipeline and Pypeit software. The resultant spectrum/emission lines allow us to measure the LRD’s black hole mass, bolometric luminosity, and Eddington ratio. Deriving these quantities enables us to examine the relationship between the black holes and their host galaxies as seen in high-redshift LRDs and better understand the anatomy, activity, and origins of supermassive black holes and this population of “Little Red Dots.” Generally, we extrapolate our findings to understand how objects in the early Universe differ from or influence what we observe in the local Universe.

Large, energetic accretion events have been observed in the inner disks of young stars and protostars. Modeling of these “FU Ori” outbursts predicts the presence of an infrared precursor before the optical peak, caused by the inwards movement of a high-temperature, high-density accretion wave which begins at approximately 1 AU. Whether or not these infrared precursors can be detected depends on the degree of extinction of the accretion disk from the dusty, infalling protostellar envelopes commonly found around FU Ori objects. To explore this question, we combined these outburst models with a disk and envelope component, using the radiative transfer simulation RADMC3D, in order to determine the viability of observing the spectra of these infrared precursors with realistic density distributions. We find that, for envelope mass infall rates typical of protostars, the infrared precursor is only conclusively apparent when viewed along an outflow cavity. At inclinations free of disk shadowing, the outburst may still be detectable.

A deeper understanding of the masses of galaxy clusters, which consist of both baryonic and dark matter, will lead to better constraints on cosmological parameters. Because cluster masses are not directly measurable, we can determine the masses of galaxy clusters by estimating their internal dark matter velocity dispersions, which are inferred from velocity dispersions of satellite galaxies within each cluster. However, because satellite galaxies are biased tracers of dark matter density and velocity fields, a velocity dispersion bias is introduced. Recent cosmological simulations indicate a ‘brighter is cooler’ effect: galaxies with larger stellar mass exhibit a slightly smaller normalization in the velocity dispersion-total mass scaling relation than galaxies with a smaller stellar mass. We confirm this expectation on a percent-level by utilizing empirical data from large surveys within an ensemble velocity likelihood model.

Hot Jupiters are giant gaseous exoplanets in close orbits to their host stars. Their proximity results in high (T>1000 K) atmospheric temperatures, providing the best opportunity for observational characterization to date. High-resolution emission spectroscopy has been on the frontier of characterizing hot Jupiter atmospheres, as the spectral features of these atmospheres provide critical insights into their atmospheric dynamics and composition. In particular, hot Jupiter atmospheres are expected to exhibit large day-night temperature differences, suggesting that the emitted spectra may vary depending on the region of the planet under observation. While 3-D models of hot Jupiter atmospheres exist, isolating and analyzing spectral features from specific atmospheric regions has yet to be explored. In this project, we have adapted code to calculate regional spectra and analyze the spectral features using 3-D atmospheric models of the quintessential hot Jupiter WASP-76 b. We find differences in spectral features between the east and west sides of the planet, which may likely indicate distinct chemical and thermal structures for each region. This project expands the field’s knowledge of exoplanet atmospheres by understanding their physical properties regionally rather than exclusively globally. Combining this with cutting-edge observational techniques, we can further our understanding of hot Jupiters as complex 3-D objects.

Currently, there is a gap in the detection of exoplanets and exosatellites transiting low mass stars. We aim to identify a star forming region with high yields for exosatellite transits around brown dwarfs to analyze using the Wide Field Instrument (WFI) on the Roman telescope. We identified the Upper Scorpius (Upper Sco) cluster as one potential region with a high clustering of brown dwarfs. We plan on fitting an IMF based on the magnitudes of the stars predicted to be in this region to estimate the number of yet-to-be-detected low mass substellar objects. We conclude that Upper Sco will be a good region for characterizing atmospheric variability of substellar worlds and detecting exosatellite transits.

Globular clusters (GCs) are useful signposts of the accretion of satellite galaxies and kinematic probes that reach far out into the dark matter-dominated galactic potentials. However, GCs are challenging to distinguish from foreground stars and background galaxies, and thus very little is known about their distribution very far from their host. The Andromeda Galaxy (M31) is an excellent example for studying GCs, with an exceptionally complete GC catalog within a projected radius rproj of 150 kpc; yet, only two GCs are known beyond rproj > 150 kpc. Our goal is to determine if more GCs lie past rproj > 150 kpc with g ≲ 18.5. Using archival data from Pan-STARRS DR1, WISE, and Gaia, and a set of color, magnitude, and profile criteria in combination with visual inspection, we were able to recover 111 confirmed GCs within 150 kpc with only 2 background galaxies contaminating our sample. Of these confirmed GCs, 70% were not in our training set and illustrate the effectiveness of the selections. We have searched to rproj ∼ 600 kpc, finding 255 candidates. Visual inspection and previous spectroscopy show that many candidates were background galaxies or foreground stars. We discovered 8 GC candidates up to rproj ∼ 500 kpc from the center of M31. Using the Hiltner 2.4 meter telescope at the MDM Observatory, we obtained spectra with high enough S/N to obtain radial velocities for 6 of the 8 candidates. The velocities are consistent with MW star velocities, and allow us to rule them out as GCs. The remaining two candidates require photometry to confirm or deny their GC status.

Galaxy clusters are the largest gravitationally bound objects in the universe, and analysis of their mass distribution and dynamical state informs our understanding of their evolution across cosmic time. Using new NIRCam/F150W2 and F322W2 imaging from the Strong LensIng and Cluster Evolution (SLICE; Cerny et al. 2025) JWST program, we present the first strong gravitational lensing model for the cluster PSZ1 G118.46+39.31 (z = 0.3967). We utilized the broad coverage of the SLICE extra-wide JWST filters to make new identifications of lensed galaxies that are not visible in HST, either because they are obscured by dust or at high redshift, to model the cluster’s mass distribution. The modelling process is currently ongoing as the gravitationally lensed galaxies used to build the model do not yet have spectroscopic redshift measurements. However, the model shows a promising ability to map the mass distribution of the cluster, as the mass peaks produced by the model align well with Chandra imaging of the cluster’s X-ray gas. The mass of the cluster estimated from X-ray observations is 6.00 x 10^14 Msun. We find the mass of the main cluster to be 1.5 ± .005 x 10^14 Msun within 170 kpc, the mass of the east subcluster to be 0.67 ± .006 x 10^14 Msun within 110 kpc, and the total mass within 500 kpc to be 10.4 ± 0.07 x 10^14 Msun.