Avery Abramson
The Capacitance and Magnetism Exploration of Lunar Swirls (CAMELS) Mission
Lunar swirls are areas of high albedo material that form distinct spiral patterns on the Moon’s surface and are related to regional magnetic fields. According to the solar wind shielding model theory, the light-colored, high albedo regolith comprising a lunar swirl results from the lunar swirl’s respective regional magnetic field’s ability to deflect solar winds. In contrast, the lunar swirl’s peripheral regolith is darker in appearance due to bombardment from solar winds. Research has indicated that areas of dark regolith between lunar swirls are lower in titanium content compared to the light-colored regolith within lunar swirls. The correlation between lunar swirls and the Moon’s irregular magnetic field therefore present lunar swirls as prime targets of investigation for advancing knowledge of space weathering and lunar crust and surface processes. Motivated by section Q5.2b of the 2023–2032 Planetary Science and Astrobiology Decadal Survey, the Capacitance and Magnetism Exploration of Lunar Swirls (CAMELS) mission will conduct further study of lunar swirls by using a satellite system of LunaSATs developed by The Great Lunar Expedition for Everyone (GLEE). LunaSATs are equipped with accelerometers, magnetometers, and capacitance sensors to measure the magnetic fields and regolith composition both in and around a lunar swirl. Vector maps generated from the CAMELS mission are expected to reveal constant changes in the behavior of a lunar swirl’s magnetic field, and data from the capacitive sensors might indicate that a lunar swirl’s regolith has a lower capacitance than its external regolith. If these predictions are accurate, the CAMELS mission will succeed in providing evidence for the solar wind shielding model theory and contribute valuable insights into the nature of the Moon’s magnetic field and regolith chemistry. The unique aspect of the CAMELS mission is its use of a satellite system directly on the Moon’s surface, allowing for a new perspective of a lunar swirl’s magnetic field. As such, results from the CAMELS mission can be compared to existing magnetic vector maps of lunar swirls generated using orbital satellites and machine learning techniques. These comparisons will also assist with validating previous studies’ data. Furthermore, understanding how regional magnetic fields protect certain areas of the lunar surface from solar radiation can aid in developing improved means of radiation protection for astronauts in space, including those involved in the Artemis program.
Refa Al-Amri
A JWST View of the Central Stellar Kinematics in M87
The black hole (BH) in the giant elliptical galaxy M87 is one of the most well-studied black holes in the local universe, with black hole mass (M_BH) measurements from both stellar and gas dynamics. However, different measurement methods yield varying results. To obtain the most robust stellar dynamical measurement for this key anchor to the upper end of the M_BH and host galaxy relations, we acquired high angular resolution and high signal-to-noise spectra from JWST. Here we present the observations from the central 3×3″ of M87 using the NIRSpec integral field unit covering a wavelength region of 1.66-3.17 microns. We show preliminary results for the measured stellar kinematics in this region.
Eric Caballero, Yuqing (Nerwen) Cao, Mike Jennings, Nachiket Yadav
White Dwarfs as Probes of Long-term Planetary System Evolution
White Dwarfs allow us to study the long-term fate of planetary systems similar to our own. Due to destabilization of the orbits by the mass loss of the central star, disks of rocky debris can be produced in these systems. The ratio of the luminosities of debris disks to their central white dwarfs are plotted, using data from Fusillo et al, Rochetto et al, and GAIA DR3. A high concentration of White Dwarfs with cooling times (since their formation as white dwarfs) from 200 Myr to 700 Myr is observed with fractional luminosities of 0 to 3%. This indicates that the stellar system is relatively stable up to 200 Myr after its host star finished its mass loss on the way to becoming a white dwarf. Our models show a gap of WDs at ~750 Myr to ~1000 Myr. This gap may be explained by a lack of sample size or undiscovered phenomena while White Dwarfs age. Understanding the makeup of WDs and their disks will provide further insight into the processes that our Solar System will go through in the distant future.
Lipika Chatur
Understanding the Evolving Distribution of Satellite Galaxies Around the Milky Way
The Milky Way (MW) is surrounded by dozens of satellite galaxies spanning nearly six orders of magnitude in stellar mass and nearly three orders of magnitude in size. The vast majority of this diverse population is constituted of ultra-faint dwarf galaxies, some of the oldest stellar systems in the Universe. Understanding the abundance of these satellites and their radial distribution, therefore, provides insight into galaxy formation and the microphysics of dark matter models. Using the predicted orbital histories of galaxies around the MW and the Large Magellanic Cloud (LMC) calculated from methods of Patel et al. 2020, we investigate the evolution of the radial distribution of satellites galaxies around both the MW and the LMC. These radial distributions can provide helpful insight into the selection criteria used to identify LMC satellites and to differentiate between MW-mass halos that do and do not experience a recent group infall. Furthermore, they provide a counterpart to observations of MW and LMC analogs to help place our galactic neighborhood in a cosmological context.
Olivia Cooper
First Results from WERLS: Tracing Ionized Bubbles with Keck and JWST
Characterizing galaxies <1 Gyr after the Big Bang is crucial for constraining the main sources of reionization, the last major phase change of the Universe from a neutral to ionized intergalactic medium (IGM). We present the Web Epoch of Reionization Lyman-alpha Survey (WERLS), a spectroscopic redshift survey using Keck/MOSFIRE+LRIS to target Lyman-alpha emission from ~800 already identified UV-bright galaxies embedded in the Epoch of Reionization (EoR). Here, I discuss early results from WERLS targets detected with MOSFIRE at z~7-8, and synergy with Cycle 1/ERS JWST NIRCam imaging. WERLS is designed to be a pre-follow-up survey for the first large extragalactic imaging surveys from JWST over 0.7deg^2: COSMOS-Web, PRIMER-UDS, and CEERS. So far, these programs have already resulted in detections and new discoveries of galaxies in the EoR, and will allow us to map the galaxy distribution in large scale structure on 10-100Mpc scales. With WERLS, we will directly compare the Lyman-alpha-inferred location of ionization bubbles to underlying galaxy density maps measured via deep NIRCam imaging to constrain the galaxies responsible for reionization and map ionized bubbles in the IGM on large scales.
Silvana Delgado Andrade
Jeans Models of Fast-Rotating MASSIVE Early-type Galaxies
Detailed studies of local massive early-type galaxies (ETGs) are essential for informing galaxy formation and evolution models. ETGs are broadly categorized into fast and slow rotators, each with distinct kinematic characteristics, photometric properties, and growth channels. We present stellar-dynamical models for fast-rotating galaxies in the MASSIVE Survey, an integral-field unit (IFU) and photometric survey of the most massive ETGs with stellar masses greater than 10^{11.5} M_\odot within 108 Mpc. We fit large-scale stellar kinematics measured from the Mitchell Spectrograph IFU on the 2.7m telescope at McDonald Observatory and deep K-band imaging from the Canada-France-Hawaii Telescope with Jeans Anisotropic Models (JAM). From these models, we determine stellar mass-to-light ratios, which can be compared to the mass-to-light ratios derived from stellar population studies to learn about variations in the initial mass function. We also measure dark matter fractions within an effective radius and the orbital anisotropy, all of which provide insight into the assembly histories of ETGs. The JAM results for the sample will be compared to future axisymmetric and triaxial orbit-based dynamical models, enabling an assessment of the impact on the inferred parameters due to different underlying modeling assumptions.
Trevor Erwin
The Distribution of Hollow Spheres in Exoplanet Transit Spectra
The James Webb Space Telescope (JWST) will allow for continuous wave-length coverage of transit spectra from the mid optical to mid-infrared for the first time (Stevenson et al., 2016). Such broad wavelength coverage necessitates a reassessment of how aerosols are modeled, specifically, particles that deviate from perfect spheres. This paper discusses how aerosol species of various size and shape distributions will appear in JWST transit spectra, specifically focusing on deviations from spherical particles. We modeled nonspherical particles using the distribution of hollow spheres (DHS), a computationally efficient model that approximates the distribution of small, randomly oriented nonspherical particles (Min, M. et al., 2003). Incorporating DHS theory allows for a general model of clouds and hazes, altering features present in the classical Mie scattering model (Min & de Koter, 2005). By incorporating DHS into existing transit spectra code, we can create a model that will allow for much more precise measurements of various clouds and hazes in exoplanet atmospheres. If nonspherical particles are affecting transit spectra to a significant degree above noise, it will become necessary for other studies to consider the effects in future transit surveys.
Junehyoung Jeon
Observability of Low-Luminosity AGN in the Early Universe with JWST
Active galactic nuclei (AGN) in the early Universe are thought to be prominent sources of energy and ionizing photons that affected the growth of their host galaxy and their environment. However, it is still unclear how the supermassive black holes (SMBHs) that fuel these AGN grew to the observed high masses already at high redshifts. Observations of high-redshift SMBH progenitors or lower-luminosity AGN will thus help characterize the evolution of SMBHs and their impact on the surroundings. With the launch of the JWST, fainter objects at high redshifts can now be detected, including lower-luminosity AGN. We assess the observability of such low luminosity AGN, using the cosmological simulation code GIZMO to provide a realistic environment for black hole growth in the early Universe. Soon after the first stars are born in the simulation run, we insert stellar-remnant black hole seeds of various initial masses, between 300 and 10^4 M⊙, at the center of a dark matter halo and follow their growth until z∼6. Such stellar black hole seeds placed in a typical high-z environment do not significantly accrete and grow to reach masses that can be observed with the JWST under conditions of standard Bondi-Hoyle accretion, as energy input from stellar feedback and chaotic dynamics prevent efficient gas accretion onto the black holes. To be observed with the JWST, rarer but still physically feasible growth regimes, involving Eddington or super-Eddington accretion, would be required. Alternatively, AGN observability may be boosted under even rarer conditions of extreme gravitational lensing.
Ananya Kaalva
Pre-Stellar Gas Evolution Analysis using STARFORGE Simulation Data
Characterizing star formation is a difficult task due to the myriad of physical properties involved in the process. The Star Formation in Gaseous Environments (STARFORGE) Project is a novel star formation simulation initiative which aims to address this by taking all forms of stellar feedback physics into account when numerically simulating the time evolution of giant molecular clouds (GMCs), including stellar radiation, stellar winds, protostellar jets, and type II supernovae. This makes STARFORGE a useful method to accurately track the evolution of each gas parcel that eventually accretes onto each star. I present the results of a STARFORGE simulation of a 2000 solar mass GMC, specifically the evolution of the mass, velocity dispersion, virial parameter ratio, and effective radius of the gas that forms each star. By analyzing the pre-stellar gas properties we aim to identify characteristics that distinguish star-forming gas from external dense gas present in the cloud.
Eugene Lee
Evolution of Galaxy Size in the FOGGIE Simulation
Cosmological simulations are a powerful tool to study galaxy evolution as they can span a substantial fraction of the cosmic time. In this research note, we use the Figuring Out Gas and Galaxies In Enzo (FOGGIE) simulations— cosmological hydrodynamic simulation of Milky Way-like galaxies— to measure the evolution of the radius of the galaxy disk. Additionally, we analyze the simulations along three different lines of sight. Lastly, we show that the disk size increases over time regardless of angle of projection.
Micah Marks
Optical Analysis of a Newly Detected Restarted Radio Galaxy
Radio galaxies are characterized by giant regions of radio emission extending from a core engine at the center of the galaxy. These galaxies go through cycles of activity, in which phases of quiescence can be followed by repeated activity of the central supermassive black hole. What we are still far from understanding is how these alternating phases of Active Galactic Nuclei (AGN) activity are reflected in the optical properties of the host galaxy. To investigate this question, we analyzed the optical Sloan Digital Sky Survey spectra of one newly found restarted radio galaxy that was radio-selected using observations from the LOw Frequency ARay. In this poster, we present the analysis of its optical properties utilizing [OII] and [OIII] emission lines, along with measurements of u-r color and the D4000 break. We use these metrics to make comparisons to those of active, restarted, and remnant radio sources from the literature of previously selected AGN from the Lockman Hole region.
Mahan Mirza Khanlari
Exploring HI Density up to ~1Mpc Around Lyman Alpha Emitters in HETDEX
The distribution and kinematics of neutral Hydrogen (HI) gas provide key insights into the large-scale structure and dynamics of the Universe. Leveraging the HETDEX dataset, we examine the HI gas column density near and between Lyman Alpha Emitters (LAEs) spanning z~1.9-3.5. The Lyman Alpha absorption line, which results from HI absorption of integrated Extragalactic Background Light (EBL), serves as our primary observational tool. We stack ~2 million fiber spectra from 55000 LAEs, ensuring a strong Signal-to-Noise Ratio. We detect absorption up to ~1Mpc around an average LAE (z ~ 2.6), where the absorption decreases as we increase the radius. LAEs in low density regions exhibit minimal absorption. We also explore the HI gas between pairs of LAEs up to ~2Mpc. We find a clear correlation between LAE pair separation and HI column density, with LAEs that have a larger separation showing less absorption. These results can be used as an empirical map of HI gas filaments that can be compared to theoretical models. The analysis employs a custom machine learning pipeline, refining LAE selection and reducing false positives. This study deepens our understanding of gas filaments and galaxy evolution, paving the way for in-depth research into the symbiotic evolution of LAEs and surrounding HI gas.
Neel Nagarajan
Chemical Compositions Of Red Giant Stars In The Old Open Cluster NGC 7789
Red giant stars usually contain negligibly small lithium abundances. This is expected, since when main sequence stars evolve into red giants, the surface lithium is convected deep into their interiors where nuclear reactions convert it into other elements. However, around one percent of red giants have been found to be unusually lithium-rich, sometimes with even more lithium than is typically observed in main sequence stars. Two stars in the open cluster NGC 7789 were previously observed to be lithium rich- NGC 7789 193 and NGC 7789 301. Both as of the time of beginning this study had not had their lithium abundances examined again for 35 years, making them an exciting target to perform high resolution spectroscopy on using the improved technology of today. We have gathered optical-region spectra, derived model atmosphere parameters, and computed thorough elemental abundances for 15 red giant stars in the open cluster NGC 7789, including stars 193 and 301. We especially focused on the lithium and CNO abundances, since they provide clues to evolutionary changes associated with internal fusion events and chemical mixing. We confirm and extend the report from the earlier study that stars 193 and 301 have anomalously large Li abundances, and that these values are apparently unconnected to any other elements’ abundances in these stars. These stars also show relatively low C12/C13 ratios compared to other cluster members, suggesting that these stars are relatively evolved. A companion study of the He I λ 10830 lines in several NGC 7789 cluster members as well as a number of field stars shows that star 301 has a strong He 10830 spectral feature while star 193 does not. Possible explanations for the large Li abundances of these stars include helium flash-induced chemical mixing events and binary interactions at some past or present times. In either case, an internal eruption of energy could cause fresh synthesis of lithium via the Cameron-Fowler Berillyum transport mechanism. Rapid transport of lithium to the outer layers via convection may explain our observing the enhanced lithium levels in their spectra, and may have created significant chromospheric transient disturbances, producing enough helium ionization to allow for the strong He 10830 absorption in star 301. These results are based on observations obtained with the Tull Spectrograph aboard the 2.7 meter Harlan J Smith Telescope at McDonald Observatory. We acknowledge support from NSF grant AST-1616040 (CS). We also appreciate additional financial support and resources from the University of Texas at Austin’s Astronomy Department and the College of Natural Sciences.
Carolina Navarrete
An Exploration of Retrieval Choices for JWST Transit Spectra of Hot Jupiters: Varying Sampling, Algorithms, Wavelength Coverage, Spectral Resolution, and Multi-Dimensionality of Models.
Among the various methods for characterizing exoplanet atmospheres, transit spectroscopy has proven to be the most prolific. Hot Jupiters, while relatively rare, have emerged as favorable targets for spectral analysis. Their hot temperatures, close proximity to their host stars, and low-density atmospheres enable unparalleled insight into their structure and composition. Previous studies that investigated the atmospheres of Hot Jupiters using transmission spectroscopy were hampered by restricted wavelength coverage. Superior quality data demonstrated by JWST ERS and cycle 1 is pushing the community to upgrade their analysis methods to extract as much detail as possible. In our project, we assess to what degree the expanded wavelength coverage offered by JWST necessitates further complexity beyond the first generation of one-dimensional retrieval frameworks. We conducted several studies investigating trade-offs between wavelength coverage and signal-to-noise ratios. As part of this project, we have made significant improvements to the existing transit modeling and retrieval code, METIS, making it more suitable for application to real transit observations. Notably, we have incorporated Hamiltonian Monte Carlo techniques for parameter retrievals in our transit spectral analysis, a departure from previous Markov Chain Monte Carlo (MCMC) and nested sampling methods. We anticipate that it will be useful for multi-dimensional models and joint analysis of multiple datasets, as HMC has demonstrated to converge more robustly than MCMC for models with large numbers of parameters in other applications.
Marissa Perry
Spurious Source Rejection Algorithms for Galaxies from JWST
Our research group aims to understand the epoch of reionization by studying early galaxies of redshift 6-8 and their evolution. Studying these galaxies gives us insight into the assembly of the early universe, the formation of early stars and galaxies, and their evolution to present time. For this study, we look at photometrically imaged NIRcam sources from JWST CEERS surveys. Our goal is to visually inspect a large chunk of sources and filter out spurious galaxies (false detection of galaxies) which we do so by detecting errors: point sources, diffraction spikes, bad sensor readings, box pixels, etc. Additionally, we look for minimal error in the spectral energy distribution (SED) plots and visually analyze the photometry of various wavelength filters. For confirming our judgement of visually inspecting the plots, we used two image classification algorithms. First, the t-Distributed Stochastic Neighbor Embedding (t-SNE) dimensionality reduction technique was implemented along with a clustering algorithm (Gaussian Mixture Model). Next, a convolutional neural network pipeline was also implemented to classify these images. Performances are compared between the clustering and CNN algorithm. The dataset which all above criteria signifies potential candidates for clustered galaxies that we may further use for research.
Kaila Ronayne
7.7 μm PAH Star Formation Rate Calibration with JWST MIRI
We test the relationship between (dust-corrected) UV-derived star formation rates (SFRs) and the 7.7 μm polycyclic aromatic hydrocarbon (PAH) luminosities from the integrated emission of galaxies at z = 0-2. We utilize multi-band photometry covering 0.2 – 160 μm from HST, CFHT, JWST, Spitzer, and Herschel for field galaxies in the Cosmic Evolution Early Release Science (CEERS) Survey. We perform spectral energy distribution (SED) modeling on the galaxies and use these data to measure dust-corrected UV-based SFRs. We also model the JWST/MIRI 7.7-21 μm CEERS imaging to derive a rest-frame 7.7μm luminosity, (L_770), using the average flux density in the rest-frame MIRI F770W bandpass. We observe a correlation between rest-frame 7.7μm luminosities and the dust-corrected FUV luminosities, with this we derive a single-wavelength SFR calibration to estimate the total SFR from the rest-frame 7.7μm luminosity. The SFR estimates from the single-wavelength calibration correlates with SED-model estimated SFRs with a scatter of 0.24 dex. We also derive a multi-wavelength calibration, which considers the total SFR to be a combination of the obscured and unobscured SFR, for the dust-corrected FUV luminosity using a linear-combination of the rest-frame observed FUV and 7.7μm luminosity. The SFR estimates from the multi-wavelength calibration correlates with SED model SFRs with a scatter of 0.23 dex. Overall, we find that the 7.7μm luminosity correlates with the total SFR estimated from the UV for massive heavily obscured galaxies, but diverges from the UV-based SFRs for galaxies at lower metallicities, low dust obscuration, and for galaxies dominated by more evolved stellar populations.
Victoria Salazar
Using Mg II Doublet Ratios to Predict the Escape Fraction of Lyman Continuum from Fourteen Galaxies
The gas between galaxies in the early universe absorbs ionizing photons, so it is impossible to directly observe ionizing photons escaping from galaxies during the epoch of reionization. The best way to trace the escape of ionizing photons is through tracers of neutral gas, such as Mg II. We aim to test the efficiency of Mg II tracing LyC escape fraction with a sample of 14 bright Mg II emitters found in the HETDEX survey for which we will get Lyman continuum photons observations with upcoming HST/COS observations. These galaxies were selected solely from their Mg II emission properties, and, unlike previous samples, no other requirement. Using the LRS2 instrument on HET we measured the Mg II doublet emission lines to determine the flux ratio of the two Mg II lines (R = λ2796/λ2803). These R ratios and the dust attenuation of each galaxy will be used to predict the escape fraction of the LyC for each galaxy. In addition, the measurement of the [OIII]/[OII] optical lines are used to determine the escape fraction of each Mg II doublet emission lines. Using each Mg II escape fraction and the dust attenuation we can predict the LyC escape fractions. We discuss significant correlations that we discovered between the LyC escape fraction and the host galaxy properties. Future work will consist of comparing these three predicted LyC escape fractions to the observed escape fraction by HST/COS to determine if Mg II and dust alone are enough to predict the observed LyC escape fraction. This will provide the template for future studies of high-redshift galaxies with JWST.
Sujay Shankar
Precision Fundamental Stellar Properties with Interpretable ML
Precomputed synthetic spectral model grids have tremendous impact across astronomical applications from galactic SEDs, to fundamental stellar properties, to substellar atmospheric characterization. However, as data quality and quantity has grown, limitations of these models have become increasingly acute. Three problems predominate: 1) incomplete knowledge of input physics and chemistry yield imperfections in the synthetic spectra, 2) the exponential scaling of brute-force grid computation limits the number of explored parameters to 3-5, and 3) coarse sampling across the grid dimensions obscures non-linear trends in spectral line properties. Here we present an interpretable machine learning emulator aimed resolving these issues. We demonstrate full-grid emulation on PHOENIX (Husser et al. 2013) by extending the cloning procedure introduced in the blasé framework (Gully-Santiago & Morley 2022) to up the maximum of 30,927 individual grid points. This technique enables the extraction of fundamental stellar parameters—Teff, log(g), and Z—for stars across the HR diagram, and serves as a stepping stone for Extreme Precision Radial Velocity (EPRV) analysis needed to identify Earth-like planets around Sun-like stars. Our approach can be extended to brown dwarf spectra such as the Sonora family of models, which involve the physics of clouds and exoplanet chemistry. We visualize discrete surfaces of the whole PHOENIX grid as heatmaps of line properties, and discuss tradeoffs of machine learning strategies to train surface regressors across the entire grid volume. The overall procedure acts to distill stellar atmosphere data into line-by-line trends that can later be refined from data. Our ultimate goal is to create a semi-empirical model: rooted in physics but informed by observations, making previously static models tunable and therefore useful to a wider variety of applications.
Isa Slavin
Contributions of AGB Stars to Galactic Nucleosynthesis
How much of the Galactic content of trans-iron group elements (those heavier than element Z = 30 or so) are synthesized by Sun-like stars of approximately 1- 8 M$_{\odot}$ ? In this poster, I examine the actual amounts of these elements relative to H that are produced by slow neutron captures (the “s-process”) during the Asymptotic Giant Branch (AGB) stage of the lives of these stars, and how these amounts vary according to initial mass and metallicity. The present-day composition of the interstellar medium – and the new stars that form from it – is partly determined by s-process-enriched material expelled by such stars, which eventually forms a planetary nebula. By examining the predicted amounts of trans-iron elements in the outer layers of such stars at the end of the AGB according to current theoretical models, we can construct an accurate inventory of their role in increasing the concentration of these heavy elements in the Galaxy. We concentrate on models of AGB evolution for 2 and 3 M$_{\odot}$ stars and the corresponding nucleosynthesis of elements with atomic numbers Z = 32-60 that takes place during this stage. Stars in this mass range, and with metallicities of about one-fourth solar to solar, exhibit the most prolific s-process synthesis of these elements. We will ultimately compare these predictions with observations of selected s-process products in Milky Way planetary nebulae whose progenitor stars had initial masses and metallicities consistent with these parameters. This work is being supported by the NSF grant AST-2307117.
Urvi Thakurdesai
Spurious Source Rejection Algorithms for Galaxies from JWST CEERS
Our research group aims to understand the epoch of reionization by studying early galaxies of redshift 6-8 and their evolution. Studying these galaxies gives us insight into the assembly of the early universe, the formation of early stars and galaxies, and their evolution to present time. For this study, we look at photometrically imaged NIRcam sources from JWST CEERS surveys. Our goal is to visually inspect a large chunk of sources and filter out spurious galaxies (false detection of galaxies) which we do so by detecting errors: point sources, diffraction spikes, bad sensor readings, box pixels, etc. Additionally, we look for minimal error in the spectral energy distribution (SED) plots and visually analyse the photometry of various wavelength filters. For confirming our judgement of visually inspecting the plots, we plan to use the t-Distributed Stochastic Neighbour Embedding (t-SNE) dimensionality reduction technique to classify the galaxies as good or bad sources and further implement a clustering task to our filtered dataset by using the Gausian Mixture Model clustering algorithm. The dataset which all above criteria signifies potential candidates for clustered galaxies that we may further use for research.
Jordan Thomas
Characterizing Stellar Jitter with Fe-I Lines for Precise Radial Velocity Measurements
The radial velocity (RV) method is currently the most versatile exoplanet detection method. The method works by measuring Doppler Shifts in a star’s spectrum, indicating the presence of a planet gravitationally pulling on it. However, the RV method is currently limited in its ability to detect earth-mass planets orbiting sun-like stars because the RV shifts created by low-mass exoplanets are smaller than those created by astrophysical noise, or “stellar jitter,” which obscure the signal. To characterize the physical sources of this noise, we utilized the StellarBox code, which are 3D radiative hydrodynamics models of the upper stellar convection zone and lower atmosphere, along with the SPINOR code to generate synthetic line profiles for HD 209458, a sun-like star with a known exoplanet. This allowed us to simulate physical processes on the star to determine their effects on the mean line profile across multiple Fe-I lines, allowing us to determine the impact of various physical processes on the shape of the line profiles in a star’s spectrum, and thus the resulting false RV shifts from stellar jitter. In the future we would be able to do Fourier analysis to determine the signal generated by stellar jitter so that it could be filtered out of a star’s spectrum to reveal hidden exoplanets.
Zhilong (Franklin) Wang
A Gemini Large and Long Program: Stellar kinematics from nearby galaxies
The masses of supermassive black holes (SMBHs) are known to tightly correlate with the properties of their host galaxy, suggesting that SMBHs and galaxies co-evolve. As such, robust SMBH mass measurements are required to properly characterize the relationships and to understand the underlying physics driving them. However, most of the previous SMBH mass determinations have been made in galaxies with small sizes relative to the local population at a given luminosity. Our work aims to address this troublesome bias using Gemini NIFS behind laser guide star adaptive optics, complemented by HST imaging observations and large-scale integral field spectroscopy, to detect and weigh SMBHs in 31 nearby galaxies. We show results of stellar kinematics extracted from galaxies observed by NIFS and discuss work to measure large-scale kinematics from HET LRS2 and VIRUS-P/W on the 2.7m Harlan J. Smith telescope at McDonald Observatory.