ABSTRACTS

Strong Lensing In the Era of Survey Science: Characterizing Large Samples of Lensing Systems

Since the advent of large-area, high-quality astronomical surveys strong gravitational lensing has transitioned from a small-N to a large-N discipline. Galaxy cluster scale strong lensing, in particular, holds tremendous untapped potential because it lies at the intersection of cosmology, the most massive structures in the Universe, and the magnified distant universe. Spectroscopic followup, in particular, is a crucial input for characterizing strong lensing systems as it measures redshifts for both cluster member galaxies (the foreground lenses) and high-redshift, strongly lensed background galaxies (the strongly lensed sources). The combination of spectroscopy and multi-wavelength followup with facilities such as the Hubble Space Telescope, the Chandra X-ray Observatory, and the Spitzer Space Telescope enables precise strong lens modeling of the mass distributions of the clusters. I will present results from over a decade of science based on follow-up and characterization of a sample of massive galaxy clusters that are selected purely on their strong lensing features. 

New Analysis of Cold Clouds in Perseus Spiral Arm using Blackbody Fitting 

It is well known that stars form from the gravitational collapse of cold interstellar gas clouds within galaxies, but how such clouds themselves form remains up for debate. The origins and development of these clouds should therefore be investigated. Building on research by Sato (1990) and Hasegawa et al. (1983), we are investigating a section of the Perseus spiral arm. We are developing a new method of determining the abundance of cold hydrogen gas in this region, where passage through the arm may cause the clouds to evolve. Our approach compares cold atomic gas appearing as HI self-absorption (HISA), molecular gas traced by carbon monoxide (CO) emission, and thermal radiation from interstellar dust. To test this method, we measure the intensity of the dust in the cloud as a function of frequency. This intensity is then fitted with a modified blackbody function to find the dust optical depth, temperature, etc. These values are used to determine gas properties, which is then compared with our method and Sato's and Hasegawa et al.'s to test and refine our analysis. Once our method is finalized, we will compare the gas properties (column density, grain size, etc.) implied by different studies to assess how their analytic assumptions affect our knowledge of these clouds' evolutionary states and their prospects for future star formation. This work was generously supported by the WKU Department of Physics and Astronomy.

Update on the 0.7 meter Bell Observatory Telescope

I will provide an update on our the progress with the installation and commissioning of the 0.7 m Planewave telescope system at Western Kentucky University's Bell Observatory. This upgrade is the result of a successful proposal to the NSF MRI program, involving faculty from WKU, Morehead State University, Thomas Moore University, the University of Kentucky, Northern Kentucky University and Austin Peay State University. The telescope is operational, and all systems are functioning nominally. We await the delivery of our filter wheel to begin training undergraduate student observers planning and executing science observations. We plan to make the observatory a resource available to faculty and students from across Kentucky and the region.

HD 51082: an observation and analysis of an eclipsing binary star system

Eclipsing binary star systems are sets of two stars orbiting one another, that in our plane of vision from Earth, eclipse each other. This causes variation in the brightness observed over time, creating a very distinctive light curve. The observation and analysis of eclipsing binary star systems is one of a few ways to measure basic properties of high mass stars with high precision, something that is both necessary as a foundation for astrophysics and yet severely under researched. A collection of identified eclipsing binary targets have been observed as part of an on-going research project at the Thomas More Observatory. This project focuses on HD 51082. The data obtained for this target is both spectroscopic (velocity) and photometric (brightness), and has been analyzed using the PHOEBE modeling software to make a complete solution of the binary system and individual star parameters.

Star Formation and Gas Supply Since Cosmic Noon

The green valley remains a highly researched topic in galactic astrophysics. Understanding the star formation rates, stellar mass, and HI gas content of these galaxies will tell much about how galaxies create new stars and how they evolve as a whole. We leverage both archival and new data in the highly researched Chandra Deep Field-South to study these properties over the last 7 Gyr of cosmic history.

Exoplanet Observations at The Thomas More Observatory 

The observation of exoplanets as a part of NASA’s Exoplanet Program has the ultimate goal of finding unmistakable signs of current life in other solar systems. A part of NASA’s Exoplanet program is NASA’s Universe of Learning Exoplanet Watch, whose main goal is to ensure large telescopes, like James Webb Space Telescope and Hubble Space Telescope, efficiently use their time in observing these targets through citizen observations with small aperture telescopes. The goal of this project has been to actively participate in NASA’s Exoplanet Watch program through observing the period and timing of an exoplanet eclipse and uploading observations to the American Association of Variable Star Observers (AAVSO) Exoplanet Database to be included in ephemeris calculations for NASA. Thomas More Observatory’s equipment is able to detect any planetary transit down to a 1% drop in brightness and a V magnitude of 14 or brighter. 

A New Metric for Assessing the Accuracy of Orbital Period Determinations

The APO Galactic Evolution Experiment APOGEE-1 and APOGEE-2 surveys took high-resolution H-Band spectroscopy of 657,135 stars (as of Data Release 17) and produced stellar radial velocities with of order 100 m/s precision. The combined surveys cover a base line of over 6 years (~2000 days). Of these, 34,739 stars have 12 or more epochs of APOGEE data. With these time series data it is possible to search for and characterize stars with stellar and sub-stellar mass companions. The first step of this characterization is to determine the companion’s orbit. The chi-squared space for Keplerian orbital fits is highly sensitive to the correct determination of the orbital period. In this talk, I will discuss our use of a Monte-Carlo rejection sampling algorithm call the Joker, and new metrics we can use for determining the reliability of our orbital period determinations.

New Analysis of Cold Clouds in Perseus Spiral Arm using Blackbody Fitting 

Metabolism suspension, otherwise known as cryptobiosis, is used by certain species that have adapted to survive extreme environments. Despite the rare benefit of this process, little is understood about its advantages in tardigrades; resilient microorganisms also known as water bears. To better understand the ways in which tardigrades respond to their environment we have devised several approaches to prepare for the results of our final experiment in conjunction with the High Altitude Research Project (HARP). We will test the local tardigrade populations susceptibility to freezing, drying, and the condition of a vacuum in order to predict their response to the exposure of near space-like conditions.

Cloudy, and Life, the Universe, and Everything

I will give a quick summary of Cloudy, the spectral simulation code I have been developing in Lexington since 1980, and discuss some of the questions it has been used to answer. These include testing Big Bang nucleosynthesis and understanding the origin of the atoms in our body.

OJ 287 - The binary black hole system that appears to be small

I will report Multi-wavelength Observations and Modelling of OJ 287 (MOMO) project. One of the major results of this multi-year multi-wavelength study is that the mass of the central black hole in this super-massive black hole binary (SMBHB) system turns out to be sufficiently lower than previously thought. OJ 287 shows repeated double flares every about 12 years. The most common model of this system requiresa SMBHB with a mass of 10 Billion solar masses where the periapsis precession of the secondary black hole's orbit by more then 30 degrees per orbit causes the observed double-peaked periodicity. This models made very specific predictions which our new observations revealed were not observed. More over, no other observational properties such as the host galaxy or the virial motion seen in the hydrogen emission lines agree with the 10 Billion solar mass black hole model. We estimate that the black hole mass is about a factor of 100 smaller, of the order of 100 Million solar masses. 

Updates on Jupiter's Zonal Winds and Global Modes from PMODE

The Planetary Multi-level Oscillations and Dynamics Experiment (PMODE) collected 24 nights of Doppler and polarimetric data on Jupiter from the AEOS 3.6m telescope in August 2020, in an effort to unambiguously identify the global oscillations of Jupiter. These oscillations, if detected, can be subsequently inverted to provide the first and only direct measurements of the deepest interior of Jupiter, allowing the astronomical community to search for a solid core within the gaseous layers. Here, we present updated results from the PMODE campaign, including the strictest amplitude limit to date (of 4.5 cm/s) on the global modes of Jupiter, constraints on possible excitation mechanisms for these oscillations, and an updated measurement of the Jovian zonal wind profile -- all results which may revolutionize the continued search for a Jovian core. 

Preparing for High Resolution X-ray data in the Microcalorimeter Era

A collaborative mission between JAXA (Japan Aerospace Exploration Agency) and NASA called XRISM will be launched in the year 2023. This mission will be collecting unprecedented high-resolution soft X-ray spectroscopic data from celestial objects in the universe using a microcalorimeter array. Such data will transform the study of black holes, galaxy clusters, compact objects, and the aftermath of stellar explosions, all of which are part of the hot, energetic universe. 

Cloudy conducts simulations of non-equilibrium plasma which results in predictions of X-ray lines. Since the original build of cloudy, it has undergone improvements to meet the spectroscopic resolution of missions such as XRISM. Elements between C and S show emission lines in the soft X-ray regime, of which the strongest are the H-like and He-like lines. Although, H-like and He-like atoms/ions exhibit level splitting due to quantum fine-structure interactions, {\sc cloudy} thus far have not taken these effects into account. In this talk I will present my work to further improve the microphysical calculations conducted by Cloudy by taking fine-structure splitting into consideration. This will make the Cloudy level energies and line wavelengths sufficiently accurate to study alongside the high resolution data from the upcoming X-ray missions. 

3-D Imaging: Designing an Integral Field Unit as a Primary Camera

Over the past 25 years, 3-D spectroscopy in astronomy has become practical. Integral Field Units (IFUs) combine imaging and spectroscopy, so that each pixel in the image contains a spectrum of that point. Most IFUs are optimized for spectroscopy, and there is a trade-off between imaging resolution and spectral resolution, with the cost and size of the CCD detector being a constraint on the design. But in designing one for imaging, a low spectral resolution (R~50) would allow users to simulate any filter at any redshift, ideal for extragalactic astronomy. Since no photons are blocked, all wavelengths are imaged simultaneously, speeding up multi-band imaging.

explOration of Astronomy by Kentucky Students (OAKS)

The proposed OAKS PAARE project is designed to improve access by (rural) minority students to opportunities in astrophysical research by greatly enhancing partnerships between research astronomers across the Kentucky Commonwealth. The partners are rural serving institutions such as Moorehead State and Berea University, and the astrophysics research department of the Northern Kentucky University and the University of Louisville. We propose creating a substantive and sustainable partnership spanning Kentucky to provide personalized mentoring, financial and academic support to KY undergraduates, plus the resources and opportunities to further their research and engage with the astronomical community on a national level. 

The societal goal for Astronomy as a science is to see the entry from a variety of previously underrepresented groups in the student and professional body. Underrepresented groups are women, people of color, first-generation students, and those from a poor socio-economic background and often a combination of these identities. Kentucky has some of the poorest counties in the continental United States and substantial numbers of students from these backgrounds attending university at one of its state schools, often as the first in their family. 

Professional astronomers are dispersed throughout the state in small physics departments but have banded together in the Kentucky Area Astronomical Society (KAAS). Under the KAAS umbrella, faculty have organized shared summer online classes on speciality astronomical topics and the Kentucky Area Meeting (KAM). The goal is to support early student research, e.g. a first project, a first presentation at a professional meeting and a first paper. Strong limitations to student research are financial, the hidden curriculum of academia, and familiarity with the basic tools of research. 

The aim is to bring in students from disadvantaged backgrounds in the KY state system, including the smaller, rural Universities and offer them research opportunities either at NKU and UofL or sponsor them to go to an REU experience at a national observatory, sponsored by this program. The aim is to familiarize students with professional astronomy through a series of workshops as part of the program, mentor their research with a local faculty contact for support, and financially support students to ensure they have financial stability to conduct uninterrupted research. 

Buckling instability in stellar bars using high-resolution N-body simulations

We analyze the origin of the buckling instability in stellar bars using high-resolution N-body simulations. Previous studies have promoted the nonresonant firehose instability to be responsible for the vertical buckling. We have analyzed the buckling process following the resonant excitation of stellar orbits in the bar. We find that (1) the buckling is associated with an abrupt increase in the central mass concentration and triggers velocities within the bar. The velocity field forms circulation cells, increasing vorticity, which is absent in classical firehose instability; (2) The bending amplitude is nonlinear when measured by isodensity contours or curvature of the Laplace plane, which has a substantial effect on the stellar motions; (3) The planar and vertical 2:1 resonances appear only with the buckling and quickly reach the overlapping phase, thus supporting the energy transfer from horizontal to vertical motions; (4) Using nonlinear orbit analysis, we analyze the stellar oscillations and find that stars cross the vertical 2:1 resonance with the buckling. The overlapping planar and vertical 2:1 resonances trapping more than 25% of the bar particles provide the smoking gun pointing to a close relationship between the bending of stellar orbits and the resonant action --- these particles are assuring the cohesive response in the growing vertical asymmetry. We conclude that resonant excitation is important in triggering the buckling instability, and the contribution from the nonresonant firehose instability should be reevaluated.

Cosmic Ray Variation with Weather

I present the results of a project to monitor cosmic-ray muons.  Muons are an elementary particle that result from atmospheric reactions of cosmic radiation from sources around the earth, such as the sun. This radiation reaches earth and interacts with the atmosphere to produce a shower of muon particles. Various factors affect the detection and flux rate of muons, such as altitude, solar activity, air pressure, and the angle of the detector. Using historical weather data, we are looking to see if meteorological factors such as pressure produce a noticeable effect on the rate of detection of muons. Additionally, we are creating a detector of our own design, consisting of scintillator tiles and a counting device, to be flown on a high-altitude balloon to study the effects of high altitudes on the radiation levels. 

Detecting AGN in Extremem X-ray Flux States with Swift

We will report on a long-time monitoring campaign of more than 100 Active Galatic Nuclei (AGN) with the NASA Neil Gehrels Swfit mission in order to detect AGN in extreme X-ray flux states. A detection will trigger follow up observations with two other X-ray missions, XMM-Newton and NuSTAR. The long-term Swift monitoring campaign allows us to better understand the long-term changes of the AGN properties, for example the development of the accretion rate and that of an line of sight absorber. The XMM-Newton and NuSTAR observation allow for a study of the ionized matter closest to the central super-massive black hole. These observing campaigns have been very successful over the last decade and several examples of follow-up observations will be presented and discussed. 

Galactic Archeology of Planetary Nebulae

Planetary nebulae (PNe) are envelopes of gas and dust that are ejected by stars that are 1-8 solar masses near the end of their lives. There are heavier elements present within these lower mass stars which are not readily synthesized. These elements show insight into the environment in which the progenitor star was formed. Here we present analysis of the elemental abundance of oxygen in 10 PNe using Nebular Empirical Analysis Tool (NEAT) and PyNeb. The data used in our analysis were obtained by the 4.1-meter Southern Astrophysical Research Telescope in Chile. Funding for this project is supported by 2022 NASA Kentucky Space Grant Consortium Research Experience for Undergraduates (REU-22-042).

Distance to RR Lyrae AO Tuc

RR Lyrae stars exhibit a linear period-luminosity relationship and are useful for measuring distances to globular clusters in our galaxy and nearby galaxies. Our research is a segment of an extensive effort investigating variable stars with robotic telescopes, with the primary goal of improving the period-luminosity relationship of RR Lyrae stars. We used Las Cumbres Observatory Global Telescope Network to obtain images of RR Lyrae variable star AO Tuc every four hours for three weeks in four filters: B, V, ip, and z-s. We analyzed AO Tuc’s light curves to find the period and calculate its distance. The metallicity of a star (abundance of heavy elements relative to hydrogen) can also affect the distance calculation. For a metallicity value of -0.46, the measured distance of AO Tuc is 904 ± 23 pc, and for a metallicity of -1.25, the measured distance is 993 ± 24 pc. The distance values obtained were compared with those of the Gaia Space Telescope, and two versions of Gaia data were used for comparison: Gaia Data Release 2 of 1313 ± 49 pc and Release 3 of 1253 ± 22 pc. We found that our distance value with lower metallicity is more consistent with Gaia. 

The Many Phases of the Filaments in Cooling Flow Clusters

Massive galaxies in cooling flow clusters display clear evidence of feedback from Active Galactic Nuclei (AGN). Joint X-ray and radio observations have shown that AGN radio jets push aside the surrounding hot gas and form cavities in the hot intracluster medium (ICM). These systems host complex, kiloparsec-scale, multiphase filamentary structures, mainly observed in warm ionized (10,000 K) and warm and cold molecular (<100 K) gas . These striking filaments are believed to be a natural outcome of thermally unstable cooling from the hot intracluster medium (ICM), likely triggered by AGN feedback. These structures can also serve as fuel for supermassive black holes (SMBHs). However, the details behind the formation mechanism of the filaments are still unknown, and the relationship between the gas phases of different temperature is poorly understood. By using a key novel method of blind source separation, we have isolated the hot phase of the X-ray filaments, which was blended with the bright diffuse ICM (and contaminated by cavities and fronts), to unveil its relation with the warm phase. We have discovered a tight positive correlation between the X-ray surface brightness and the Halpha surface brightness of the filaments (over 2 dex), in a sample of seven X-ray bright cooling-flow clusters, covering scales of ~5--70 kpc. This discovery provides strong evidence supporting theoretical models of Chaotic Cold Accretion and precipitation, in which the in-situ turbulent multiphase condensation and excitation mechanisms shape the tight co-evolution of the hot and warm filaments. The correlation also agrees with that found in diffuse gas in stripped tails, suggesting that such mechanisms may be self-similar over different scales and systems.

Connecting Lyɑ and LyC escape with a gravitationally lensed, super star cluster at cosmic noon

The physical processes that control the escape of ionizing Lyman continuum (LyC) photons from a galaxy are poorly understood, and are likely not isotropic. LyC escape physics should depend on the local properties of the interstellar medium, which can vary on the physical scales of individual star-forming regions. Limited instrumental coverage of resolved LyC radiation at low redshifts and the angular diameter evolution with redshift jointly mean lensed galaxies at redshifts z~2-4 offer the smallest scales we can resolve LyC escape. A valuable tool to identify LyC escape methods is Lyɑ emission, since it strongly interacts with the same HI and dust as LyC. Its complex radiative transfer process encodes significant information about the HI morphology and kinematics of the galaxy. In this talk, I will present results connecting Lyɑ and LyC escape in the Sunburst Arc, a z=2.37 strongly lensed galaxy with LyC emission resolved to a single region ≲20 pc across in a young super star cluster. The strong lensing creates multiple images of the LyC-leaking region, as well as images of different, non-leaking regions of the galaxy. We find great diversity among the Lyɑ profiles observed along different lines of sight into various locations inside the galaxy, with a differing number of peaks and relative peak strengths. We directly fit the profiles to constrain a large number of common Lyɑ parameters (such as peak separation, peak FWHM, EW, and more). Briefly, we find the leaking region has a narrow peak separation (~330 km/s), a stronger Lyɑ EW (~25 Å versus ~10 Å in the non-leaking regions), and other signatures of high LyC escape. We analyze the mutual dependence of the Lyɑ parameters, as well as their relation to LyC escape. We highlight the correlations and anticorrelations from this, and attempt to offer an explanation for the diversity of observed Lyɑ profiles. The most likely explanation supports the existence of a mirror-like HI geometry that effectively reflects Lyɑ photons into our view, far (≳270 pc) from their suspected origin in the LyC-leaking region. This might explain why we observe central Lyɑ peaks—closely connected to LyC escape—in areas of the galaxy that do not leak LyC. This would emphasize the stochasticity of Lyɑ radiative transfer and the highly complex relation between Lyɑ and LyC escape at scales resolved below the size of a galaxy. This will be an important lesson as the number of high-redshift, lensed galaxies grows and JWST and upcoming ELTs target them with unprecedented resolution.

The Analysis of Black Hole Masses Through Spectroscopy

Most galaxies have a massive black hole at their center, and these black holes grow through accreting gas from the galaxy. So, we can expect there to be a relation between galaxy mass and black hole mass. Using the spectra of several galaxies, we have measured the masses of their black holes. The gas orbiting the black holes moves at speeds related to the black hole mass, and we can measure the speeds spectroscopically from their Doppler shift. In addition to this, we have observations of the galaxy as a whole with Integral Field Spectroscopy, in which every pixel in the image has a spectrum. This way, we can measure the Doppler shift of each part of the galaxy as it orbits the center, allowing us to measure the mass of the galaxy.

Chemical abundances and ISM ionization properties of galaxies from Cosmic Noon to the Epoch of Reionization

I will present recent results based on JWST/NIRSpec rest-optical spectroscopy of star-forming galaxies spanning z=2-9, as well as results from ground-based spectroscopic surveys at z=0-3. I will discuss new constraints on the properties of the ionized interstellar medium, particularly focusing on the evolution of gas-phase chemical abundances and ISM ionization state. Characterizing the evolution of metallicity scaling relations such as the mass-metallicity relation provides powerful insight into galaxy formation and growth processes including gas inflows and outflows, while chemical abundance patterns can be used to constrain formation timescales. JWST spectroscopy is opening an era of precision chemical abundance studies of high-redshift galaxies. I will discuss upcoming JWST programs that will build on the initial work with early data and advance toward a detailed view of galaxy chemical evolution from Cosmic Noon to Cosmic Dawn.

PMODE Doppler Measurements

The physical properties of the inner cores of the giant planets are poorly known. Humanity has only been able to attempt these measurements of, in our case, the Jovian core by measuring gravitational influences from probes sent to the planet. But now, the PMODE team has constructed an instrument to observe a more indirect set of data for the Jovian core: by recording the small shifts in radial velocity of the upper cloud decks on Jupiter by using a custom instrument at Mt. Haleakala, Maui, HI, as a way to study the atmosphere and interior of the planet. This research created a rich planetary dataset, valuable to the public but unusable in its current state as all files lack necessary archival header information. Our goal is to create a program which inserts these data automatically into each of the tens of thousands of individual frames of Jupiter and upload them as a database to NASA’s Planetary Data System for the general scientific community to utilize. This will greatly facilitate the study of the Jovian core, as this project will open up a significant wealth of data for further study of Jupiter’s interior below the clouds. We present the current status of the project, the goals that we have for finishing the project, and the hopes we have for the future with this data.

Observations of the Changing-Look AGN RX J0128.1-1848

While in the standard Unified Model of Active Galactic Nuclei we distinguish between Seyfert 1 and 2 galaxies, some AGN change their type. These are called Changing Look AGN and many of them have been known for more than a decade. Recently another of this rare type was discovered by Swift in an unusual low X-ray flux state in November 2022, the galaxy RX J0128.1-1828. This discovery triggered XMM and NuSTAR observations at the beginning of January 2023. Here I will summarize the preliminary results from our Swift monitoring of RX J0128.1-1848 and well as from the XMM and NuSTAR observations.

A High Precision Survey of the D/H Ratio in the Nearby ISM

We present high S/N measurements of the H I Ly alpha absorption line toward 16 Galactic targets which are at distances between approximately 190 and 2200 pc, all beyond the wall of the Local Bubble. We find total H column densities ranging from 10^20.01 to 10^21.25/cm2, and determine the D/H ratio along the sight lines. We confirm and strengthen the conclusion that D/H is spatially variable over these H I column density and target distance regimes, which predominantly probe the ISM outside the Local Bubble. We discuss how these results affect models of Galactic chemical evolution. We also present an analysis of metal lines along the five sight lines for which we have high resolution spectra and, along with results reported in the literature, discuss the corresponding column densities in the context of a generalized depletion analysis. We find that D/H is only weakly correlated with metal depletion and conclude that the spatial D/H variability is not solely due to dust depletion. A bifurcation of D/Htot as a function of depletion at high depletion levels provides modest support that deuterium-rich gas is infalling onto the Galactic plane.

Nope! It did not do it again. The Story of IC 3599.

I will report on the long-term monitoring campaign of the Seyfert 1.9 galaxy IC 3599 by Swift, starting in 2013. IC 3599 was discovered as an extremely bright X-ray source during the ROSAT All-Sky Survey in 1991, but later pointed observations revealed a dramatic drop in the X-ray flux. One model to explain such a dramatic X-ray outburst is the tidal disruption of a star by the central black hole. However, another flare was detected in 2010 by Swift. This makes the Tidal Disruption Event (TDE) scenario less likely and favors an accretion disk instability. Nevertheless, one possibility is the partial tidal stripping of a star on an elliptical orbit around the star which would suggest a periodic flaring. In this model it was predicted that another flare would occur in 2019/2020. Our Swift monitoring clearly shows that this is not the case and that the flares can be explained by accretion disk instabilities. I will present how that X-ray and UV emission in IC 3599 has changed over the last decade and what this means for modelling this AGN.