University of Michigan Astronomy
Undergraduate Research Symposium 2023
Friday, April 14th
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Three-dimensional Mapping of the Gum Nebula
Doni Anderson (University of Michigan, Ann Arbor), Robert Benjamin (University of Wisconsin, Whitewater)
With recent advances in mapping the 3D dimensional distribution of dust near the Sun, determining the 3D structures of large nearby low-density bubbles in ISM is becoming more achievable. Using these dust maps, we worked on strategies that would allow us to find the boundary of the Gum Nebula, a nearby (300 parsecs away) large angular size (radius 15 degrees) H-alpha bubble seen in the third Galactic quadrant (Galactic longitude L=240 to 270 degrees). In the end, we found that no single automated procedure could adequately outline the boundary of the Gum Nebula, and we developed a procedure to map the extent of the Gum Nebula by eye. The boundary was mapped by looking at the density structure in slices of fixed vertical (z) height and joined together to form an estimated boundary of the Gum Nebula. We also studied the boundary in search of signs of expansion by identifying the dust clouds with HI and CO emissions features of known velocity. One significant problem we uncovered is that the full extent of the Gum Nebula has not been mapped in CO emission. With the measurement of the boundary and velocity structure of the Gum Nebula, we are now ready to create a model of the creation and expansion of this structure as well as to characterize the stellar and interstellar contents of this large HII region/supernova remnant.
This work was supported by the National Science Foundation's REU program in Astrophysics through NSF award AST-2150222.
Marcos Arias (University of Michigan), Eric Bell (University of Michigan)
We determined the structural parameters of the smallest dwarf satellite galaxies in the dark matter halo of Andromeda through a Markov Chain Monte Carlo (MCMC) maximum likelihood algorithm applied to the Pan-Andromeda Archeological Survey (PAndAS). For each satellite galaxy, the algorithm returns the centroid, exponential half-light radius, ellipticity, positional angle, number of stars, along with errors. The returned parameters, and its uncertainties are compatible with published values, and we tested the consistency of the algorithm through ratio and difference plots. The number of stars were also converted into luminosity functions that quantify the absolute magnitude of each dwarf galaxy. Consequently, the smallest and faintest dwarf satellites provide insight into the formation and evolution of galaxies and the behavior of dark matter on small scales, as they are the oldest, most dark matter dominated, most metal poor, and least chemically evolved systems. The unique features of dwarf satellites make them untouched artifacts of the early universe, thus, providing information on the conditions during the formation of the first galaxies. Our goal is to test and strengthen the developed maximum likelihood algorithm to establish robust estimates of the properties of undiscovered ultra-faint dwarfs in the halos of Andromeda and M81.
Mireya Arora (University of Michigan), Hayley Beltz (University of Michigan), Emily Rauscher (University of Michigan), Megan Mansfield (University of Arizona)
During transit, a planet’s nightside emission spectrum is often ignored, as it is thought to be too faint to detect after data reduction. We set out to test this assumption for the ultra-hot Jupiter Wasp-76b. Based on 3D atmospheric models of the planet, we simulated high-resolution transmission spectra of an ultra-hot Jupiter to explore if emission spectra could be detected via cross-correlation. To achieve this, we combined a Phoenix Library stellar spectrum with simulated transmission and emission spectra for several phases throughout transit. We perform principal component analysis on these simulated spectra to determine if emission spectra signatures remain in the simulated data. If we are able to achieve a high enough detection significance with this method, we intend to add noise to the data to simulate observations more realistically. The results will be influential in astronomy to determine if nightside data can be detected from existing high-resolution transmission data.
Alberto F. Ayerza (University of Michigan), Elena Gallo (University of Michigan), Anil Seth (University of Utah), David Ohlsen (University of Utah)
We assembled Chandra X-ray Telescope imaging data for 735 nearby galaxies to obtain a measurement of the active supermassive black hole fraction down to a uniform sensitivity threshold: 38% of the target galaxies have a nuclear X-ray source brighter than 4E+38 erg/s, below which stellar-mass compact objects are likely to dominate. This is a firm lower limit to the true black hole fraction.
4U 1700-377 in NuSTAR Stray Light
Sasha Bacon(University of Michigan), Mckinley Brumback(University of Michigan)
Lailyn Borum (University of Michigan), Ian U. Roederer (University of Michigan)
Caden Burkhardt (University of Michigan), Sally Oey (University of Michigan), Julian A. Deman (University of Michigan), Grant D. Phillips (University of Michigan)
It is theorized that a Wolf-Rayet(WR) star could evolve by being spun up in a close binary system via mass transfer. As a consequence, we expect their binary companion to explode and eject the WR star as a runaway. We analyze the transverse velocities of WR stars in the Large Magellanic Cloud in hopes of finding if any particular class of WR star corresponds to this evolutionary method. We present our preliminary results below.
Raven Cilley (University of Michigan), George King (University of Michigan), Lia Corrales (University of Michigan)
As an exoplanet passes in front of its host star, the star may dim enough for a clear dip to be shown in its luminosity. However, planets are small compared to the size of their host star, and as such the difference in luminosity is a tiny percentage of the star’s original brightness. By looking for exoplanet transits in the X-ray spectrum, the atmosphere of the planet can aid in blocking the star’s radiation and cause a larger dip. Observing transiting exoplanets in X-rays can also provide more information than visible observations about the properties of the planet and how it interacts with its host star’s intense radiation. However, X-rays are notoriously harder to measure as stars are dimmer in the X-ray portion of the spectrum, so specialized telescopes must be used. AXIS is a proposed X-ray observational satellite that would, in addition to other purposes, aid in high-energy exoplanet studies by measuring higher count rates than previously available. This project seeks to discover transit targets that are luminous enough in the X-rays that they could be studied by AXIS. To start, a sample of stars with known transiting exoplanets was taken from the NASA Exoplanet Archive, and sorted to contain nearby targets. Then, the X-ray luminosity (Lx) of each star was found by utilizing either previous measurements or known relationships between Lx and the star’s rotation period or age. These luminosities were used to calculate the X-ray flux. Finally, the theoretical count rate in AXIS of each star was calculated, the corresponding transit light curve was estimated, and the best targets were selected.
Investigating Atmospheric Dynamics of 3D-Modeled Hot Jupiters
L Cinque (University of Michigan), Isaac Malsky (University of Michigan), Emily Rauscher (University of Michigan)
Jacob Cleaver (University of Michigan), Lee Hartmann (University of Michigan), Jaehan Bae (University of Florida)
We compute model lightcurves and spectral energy distributions of accretion outburst events from protoplanetary disks. We input variable initial disk properties in order to make predictions on the amplitude and timescale of the outbursts. From previous simultaneous observations in the optical (Gaia) and infrared (NEOWISE), we anticipate an earlier observation of the outburst in the infrared than in the optical spectrum. Using this knowledge, our goal is to then create approximations of a small outburst (Gaia17bpi) and a larger outburst similar to an FU Ori outburst.
Sophia Davis (University of Michigan), Anne Blackwell (University of Michigan), Joel Bregman (University of Michigan)
Galaxy clusters are the largest gravitationally bound structure, so they should retain all metals produced by their constituent galaxies. Theory predicts that the relationship between metallicity and stellar mass of a galaxy cluster is linearly proportional. Instead, we find a Universal metallicity independent of galaxy cluster stellar fraction (M*/Mgas) and an excess of metals for the largest mass systems. We investigate a universal source of metals, the Early Enrichment Population (EEP), to explain this discrepancy. In analyzing intracluster medium spectra from various galaxy clusters, we are able to estimate the expected contribution of the EEP based on these results where ZEEP = -1.438(M*/Mgas) + (0.483). The inclusion of ZEEP greatly improves the total fit of the total metallicity.
Julian A. Deman (University of Michigan), M. S. Oey (University of Michigan), Grant D. Phillips (University of Michigan)
In recent years, evidence has emerged to suggest that luminous blue variables (LBVs) and B[e] supergiants (sgB[e] stars) may preferentially reside in the field rather than clusters. This would likely imply that they are generally objects ejected from clusters. We use data from Gaia Data Release 3 (Gaia DR3) to obtain transverse velocities for all known LBVs, LBV candidates, and sgB[e] stars in the Magellanic Clouds relative to their local field velocities. The calculated residual velocities for our LBVs, LBV candidates, and sgB[e] stars are all comparable to the velocities of OBe stars in the Small Magellanic Cloud, which are thought to result from supernova ejections in binary systems. Our results support the scenario that both LBVs and sgB[e] stars originate from post-supernova binary systems, consequently acquiring accelerated velocities.
Kaj Desch (University of Michigan), Elena Gallo (University of Michigan).
Matthew Fischer (University of Michigan), Monica Valluri (University of Michigan)
Karthik V. Ganti (University of Michigan), Eric F. Bell (University of Michigan), Adam Smercina (University of Washington), Richard A. D’Souza (Vatican Observatory)
Galaxy Cluster Mass Modeling using Simulation Based Inference
Akum Gill (University of Michigan), Humna Awan (University of Michigan), Camille Avestruz (University of Michigan), Yuanyuan Zhang (NOIRLab), Brian Nord (Fermi National Accelerator Lab), The LSST Dark Energy Science Collaboration
Marley Gonzales (University of Michigan), Nuria Calvet (University of Michigan), Marbely Milcolta (University of Michigan), Thanawuth Thanathibodee (Boston University)
The study of exoplanet formation is extremely difficult to do. Since only bright exoplanets far from its central star have been resolved, we must look to other methods for detecting them. One of these methods is through the study of spectra. In this work, we studied the spectra of 23 T-Tauri stars in the Taurus star forming region, which were obtained utilizing the MIKE (Magellan Inamori Kyocera Echelle) spectrometer on the Magellan Telescope in late 2021, early 2022. We analyzed the following emission lines: H𝝰, Ca II K, and one of the Ca II triplet lines at 8490 Angstroms. The spectra of each emission line was normalized to a continuum and converted into a relative flux/velocity scale. These emission lines are formed in the magnetospheric accretion flows through which material from the protoplanetary disk is accreted onto the central star. The aim of this work is to look for depletion in the refractory elements by looking at the strength of the lines of those elements relative to the strength of the H𝝰 line, which comes from matter accretion onto the central star. Particularly, we are interested in the Ca II lines. We see diminished flux in these lines, which indicates depletion in the protoplanetary disk of the star. This depletion means there is an object in the disk which is collecting a large amount of the refractory element Ca, creating a gap in the disk in the visible. The presence of the disk gap is often attributed to the formation of giant planets. We are actively looking for trends that will cause these depletion factors to appear more often, and what those trends can tell us about the protoplanetary disk itself.
Mayra Gutierrez (University of Michigan), John Monnier (University of Michigan)
Our project focuses on creating and flying a two CubeSats pathfinder called STarlight Acquisition and Reflection toward Interferometry (STARI). We are using drones to demonstrate that formation flying and starlight acquisition is possible and build towards a two CubeSat space interferometer. Since many biomarkers are seen in the mid infrared, a space interferometer could observe a larger part of the electromagnetic spectrum improve our ability to detect and characterize Earth-like planets. While ground based interferometers face visual turbulence, CubeSats experience physical turbulence. In our drone starlight acquisition project we have measured the vibrations of the drones and are implementing vibration damping methods. In developing a space interferometer vibration isolation obtain sufficient light coherence time and be competitive with ground-based interferometers.
Fiona Han (University of Michigan) Lee Hartmann (University of Michigan), Nuria Calvet (University of Michigan), Ramiro Franco-Hernández (Universidad de Guadalajara)
We calculate the mm-wave emission of protostellar disks models and compare them to ALMA and VLA observations of irregular objects observed in the Orion B molecular cloud. These objects are unusually bright at 0.87mm and 8mm, suggesting that they have very large dust (and gas) masses on scales <100 AU. The nature of these objects are unclear. Previous study argued that these objects are candidates for first hydrostatic cores, formed in the earliest stage of a star’s lifetime. Using computer simulations, we compute images from disk models to find possible explanations for the observed high luminosity of the HOPS 40X objects, assuming protostellar disk structures is present.
Chi Han (University of Michigan), Tyler Gardner (University of Exeter), John D. Monnier (University of Michigan), Colton Peterson (University of Michigan)
The ARMADA Survey hopes to investigate demographic information about exoplanets. We are also interested in studying stellar properties. In this study, we present a detailed analysis of HD6456, a system that consists of two A0Vnn stars. We performed isochrone fittings to obtain its total photometric mass and compared it with its dynamical mass from orbital fitting. We conclude that with a distance measurement of 87.9 +/- 0.68 pc and metallicity of -0.46, the difference between total dynamical and photometric mass is 1.12 +/- 0.12 solar masses. This result does not agree with the expectation of a brown dwarf as a third component. We investigate the correlation between metallicity and distance measurements, and we find that at the metallicity of [to be determined], the photometric and dynamical masses agree within the 1-sigma range. This result also indicates that the surface metallicity measurements do not represent the metallicity of an A star at its core. A possible explanation for this is A-stars have radiative shells. The lack of convection caused them not to be very well mixed.
Daniel J. Heilman (University of Michigan), Per Calissendorff (University of Michigan), Michael Meyer (University of Michigan)
We present the conclusions drawn from studying the spectra of extrasolar object 2MASS J08561384-1342242 (J0856) in order to determine its properties. J0856 is a brown dwarf discovered through the 2 Micron All Sky Survey (2MASS) and published in a discovery paper by Boucher et. al. (2016). It is of particular interest for a couple of reasons. Firstly, because its spectra can provide information about brown dwarfs, and secondly, because it has a circumstellar disk, despite being older than the average age at which most such disks dissipate. This peculiar feature makes it of particular interest and can potentially provide insight into the nature of circumstellar disks and “Peter Pan” disks such as this one that outlive their expected lifespan. The disks are an important feature in themselves, but are also closely related to the formation process of stars and substellar objects, and end up being the birthplace of gas giants like our own Jupiter and many other planets. This spectral analysis was done using Python in Jupyter Notebook, an open source IDE. The MIKE spectrograph was used with the Magellan telescope to collect data on the object during a six hour observation period in winter 2022. The MIKE spectrograph is a high resolution spectrograph that covers optical wavelengths between 320-480 nm in the blue and 440-1000 nm in the red and was used to look at a number of features. These include the H-alpha emission line at 6563 angstroms indicative of accretion from the disk, the LiI absorption line at 6707 angstroms that can confirm the youth of the object, and the doppler shift of such features as these. The information gathered contributes to data that gives astronomers insight into the formation and properties of brown dwarfs, other substellar objects, and circumstellar disks. Our findings can be compared to the findings presented in the discovery paper and can be used to assess membership probability of J0856 in the TW Hydrae young moving group (which our object likely fits into), as well as the Columba and Tucana-Horologium young moving groups in addition to others.
Aleck Hernandez (University of Michigan), George King (University of Michigan), Lia Corrales (University of Michigan), Raven Cilley (University of Michigan)
The near-UV and X-ray are relatively underexplored regions of the electromagnetic spectrum in terms of studying exoplanets. The GALEX telescope made UV measurements on many host stars during its lifetime, but gaps in the data have remained since its decommissioning in 2013. Our goal is to remedy this by building a catalog of UV (200-250nm) and X-ray (0.3-2.4 keV) data collected from exoplanet host stars in order to find optimal targets for NUV and X-ray transit studies.
Alicia N. Highland (University of Michigan), Ryan MacDonald (University of Michigan), Erin May (Johns Hopkins APL), and the JWST GO-1981 Team (Various)
With recent advancements in exoplanet detection, the search for life beyond Earth has become a major focus of astronomical research. A key step in assessing potential habitability within the universe is understanding the atmospheric composition of exoplanets. Exoplanets with the highest probability of life include rocky planets orbiting red dwarf stars within the habitable zone, the area around a host star in which the planet’s atmospheric conditions could support liquid water.
In this poster, we present the tentative and preliminary results of the study where we used JWST transmission spectroscopy on transiting exoplanets (specifically GJ 1132 b) to gain knowledge of exoplanet atmospheres. An atmospheric retrieval code, POSEIDON, was used to run retrievals that would characterize the chemical compositions of the atmospheres or lack thereof. The models in this program give insight on the chemical species present in the atmosphere (if any), cloud properties, temperature, and other parameters. Although our findings are still in process at the time of this poster, the final results are expected to have significant implications for the search for life outside of Earth and the future of exoplanet exploration.
Prachet Jain (University of Michigan), Shashank Kalluri (University of Michigan), John Monnier (University of Michigan)
Space-based interferometers would revolutionize observational astronomy, helping detect more cosmological phenomena in the mid-infrared wavelength range, including exoplanets with biomarkers in their atmosphere. Technological challenges have prevented the launch of a space-based interferometer, which we hope to remedy by proposing STARI: A two-element cubesat-based pathfinder mission. The ability for the two elements of the formation to maintain a precise relative distance and orientation is of paramount importance to accomplish beam transfer, but fine-positioning systems at the required accuracy level have not yet been developed for space. We propose a beacon system using LEDs for this purpose. Using a set of LEDs on one element and a camera on the other, we can deduce the relative position and orientation of one element with respect to another. This information will be fed to a control loop to adjust the relative positions and orientations in real-time. Benchtop testing is currently being carried out on our system, which will then be tested on a two-drone formation to validate our algorithms.
Michelle C. Jecmen (University of Michigan), M. S. Oey (University of Michigan)
Mechanical feedback from massive stars is strongly metallicity-dependent, and therefore low metallicity feedback should vary dramatically from that at solar. We examine the following effects relevant at low metallicity: reduced stellar winds, core-collapse supernovae starting at ages much later than 3 Myr, accretion-driven feedback, and dynamical mechanisms that remove massive stars from clusters. We use the Starburst99 population synthesis code to compare the mechanical luminosity and momentum injection rate predicted by the classical feedback scenario to models at subsolar metallicity. We find that the onset of mechanical feedback is effectively delayed until an age of ~10 Myr. This can explain high star formation efficiencies seen in super star clusters, multiple stellar populations in globular clusters, and overestimated mechanical luminosity of Large Magellanic Cloud superbubbles. Furthermore, this scenario may promote the escape of Lyman continuum radiation and may affect galactic chemical evolution.
Elise Kesler (University of Michigan), Sean Johnson (University of Michigan), Zhuoqi Liu (University of Michigan), Jonathan Stern (Tel Aviv University)
Theorized suppression of star formation by AGN outflows is a keystone of many galactic evolution models. Proposed mechanisms driving these outflows include radiation pressure and hot, shocked winds, but no conclusive model has yet emerged. Here, we examine UV and optical circumnuclear spectra from 7 galactic-scale outflows in an attempt to understand the driving mechanisms. Flux results and line ratios thus far, when compared with theoretical models, suggest these outflows are dominated by radiation pressure. However, a potential outlier indicates a potential hot wind component, which could be constrained by further diagnostics.
Maxwell Klein (University of Michigan), Keren Sharon (University of Michigan), Kate Napier (University of Michigan), Ryan Walker (University of Michigan), Grace Smith (University of Michigan), Nicole Kuchta (University of Michigan); Mike Gladders (University of Chicago); Gourav Khullar (University of Pittsburgh); Guillaume Mahler (Durham University); Antony Stark (Center for Astrophysics | Harvard & Smithsonian Center; a COOL-LAMPS Collaboration)
We present a strong-lensing analysis of COOLJ1241+2219, the brightest gravitationally lensed galaxy at z ≥ 5. Discovered by the COOL-LAMPS Collaboration (Khullar et al. 2021), COOLJ1241+2219 has a redshift of z = 5.043 and an AB magnitude z = 20.5; roughly 5 times brighter than the next brightest z ≥ 5 galaxy. This redshift places it at the end of the Era of Reionization and as such it serves as a touchstone for future research of that epoch. Its lensing cluster has a redshift of z = 1.002 and a core mass of M(<500kpc) = 7.63 ± 0.3 1013 M☉ based on our lensing model. The powerful lensing magnification in this line of sight results in high spatial resolution in the image plane, enabling detailed studies of the properties of star formation on a clump-by-clump basis. We use new Hubble Space Telescope (HST) imaging to improve upon the lens models of Khullar et al. (2021). The high resolution of the HST data reveals internal structure in the giant arc, which we use to identify 15 constraints and construct a robust lens model. This model is used to create a source plane reconstruction, extract cluster mass, and determine magnification values. All of these will support our team's forthcoming James Webb Space Telescope program to characterize the stellar mass assembly and physical properties of this high-redshift galaxy at scales that are otherwise unattainable.
Brennan J. Kompas (University of Michigan), Hirsh V. Kabaria (University of Michigan), John D. Monnier (University of Michigan)
We analyze the stability of drones for astronomy applications, with the goal of flying a drone formation as an interferometer. While commercial drones have guidance systems that ensure safe and predictable flight, they are not able to natively able to hold a tight formation. In order to best understand which flight modes are the most stable, we conducted multiple flights and compared internal drone guidance to a true position captured by an external motion capture system. We found that loiter mode provides the most stable flight and most accurate guidance position estimate.
Olivia R. Korensky (University of Michigan), Gabriele Cugno (University of Michigan), Michael Meyer (University of Michigan)
The study of protoplanets and their formation has accellerated in recent years due in the advent of the creation of telescopes with higher angular resolutions and of the adoption of more intuitive methods of protoplanet detection. Despite this, very few protoplanets have been confirmed using direct imaging methods, which are key to understanding the process (accretinary or otherwise) of gas giant formation. In our research, we use a combination Angular Differential Imaging (ADI) and Spectral Differential Imaging (SDI) to search for H-Alpha emission indicative of accretion shocks around the T-Tauri star LkCa15 in order to confirm or provide evidence to refute theexistence of LkCa15b, a controversial protoplanetary cantidate detected from H-Alpha emission (656.3nm). After reducing 4 epochs of H-Alpha High Contrast Imaging in Pynpoint, we did not detect any signals indicative of an accreting protoplanet. In order to determine the quality of our data for future research into the mass accretion rate limits of protoplanets around the star, we plotted contrast curves of our observations using the new software Applefy. We concluded that since the magnitude of contrast of each epoch of data was below that of the proposed detection in 2015 (5.2 +/- 0.3), it is less likely that that previous detection was a true protoplanet.
Nicole Kuchta (1), Keren Sharon (1), Kate Napier (1), Gourav Khullar (2), Guillaume Mahler (3), Michael Gladders (4), Håkon Dahle (5), Maxwell Klein (1), Ryan Walker (1), Grace Smith (1) | 1 University of Michigan, 2 University of Pittsburgh, 3 Durham University, 4 University of Chicago, 5 University of Oslo
The high mass of galaxy clusters makes them the most extreme examples of gravitational lensing – a phenomenon described by general relativity in which the spacetime curvature distorts light from background sources. Here, we present the first lensing analysis of COOLJ2129-0126, a strong lensing cluster studied by the COOL-LAMPS Collaboration (ChicagO Optically-selected strong Lenses - Located At the Margins of Public Surveys). Discovered using DECaLS grz imaging, COOLJ2129 was spectroscopically confirmed in August 2020 with the Nordic Optical Telescope. The cluster was found to be exceptional for both its high redshift, z=1.33, and its high mass, as evident by the large radius of the giant arc produced by the cluster at 18”. The giant arc observed in this field is just as remarkable as the foreground cluster as it is an extremely bright image of a galaxy at redshift z = 3.29. The lensing model for this galaxy cluster is based on multi-band imaging data from the Hubble Space Telescope and ground-based spectroscopy of the lens and background sources. We use these data to identify 21 constraints, primarily from key features and substructures observed in the lensed image. This lensing model is used for constraining the mass of the galaxy cluster, creating a source plane reconstruction, and finding the magnification values of the field – all parameters that are crucial in characterizing the physical processes within and the structure of both the lensing cluster and the background lensed galaxy.
Andrew R. Lapeer (University of Michigan), Monica Valluri (University of Michigan), Eugene Vasiliev (University of Cambridge), Behzad Tahmasebzadeh (University of Michigan), Matt Taylor (University of Calgary)
Ultra-compact dwarf galaxies (UCDs), characterized by their abnormally dense stellar populations and ultra-compact nature, provide a unique tool in the study of galaxy and galaxy group evolution, and possibly exist as a link between various classes of stellar systems (e.g. globular clusters, dwarf ellipticals). Central black holes in such systems not only provide a useful asset in probing the nature of UCDs, but also in the constraint of the black hole mass function in general.
This investigation aims to probe the lower limit of recoverable central black hole mass in such systems via self-consistent orbit-superposition (Schwarzschild) modeling (Schwarszschild 1979). We employ the FORSTAND code (Vasiliev & Valluri 2020), an iterative, observationally-constrained Schwarszchild modeling routine, to recover black hole mass from mock kinematic data generated from static, self-consistent N-body representations of simplified UCD-like systems. The mock data are designed to mimic the spatial and spectral resolution of JWST NIRSpec IFU data. This analysis of mock data will enable us to interpret and model IFU kinematics from a Cycle I JWST Guest-observer program. We identified a lower limit of recoverable mass of order ~106.5 M⊙, however further investigation is needed to constrain this limit to the fullest extent.
Xinyue Liu (University of Michigan), Jane Huang (University of Michigan), Edwin Bergin (University of Michigan)
Our project aims to investigate the chemical compositions and the molecular tracers of the structures in four Class I protoplanetary systems at different evolutionary stages (IRAS 04158+2805, IRAS 04166+2706, IRAS 04295+2251, and IRAS 04302+2247) in the Taurus star-forming region using the Submillimeter Array (SMA). Here, we present some preliminary and representative results of the molecular tracers of the four primary structures (envelope, outflow, disk and streamer) in Class I systems. By combining their chemical properties and their structures tracers, we can infer their evolution stage and understand the growth of protoplanetary systems better.
Aidan Meador-Woodruff, Alex Wingate, Elizaveta Gavrilova, Ryan Walker, Sanil Mittal, David Gerdes (all University of Michigan)
Sanil Mittal (University of Michigan), Ian U Roederer (University of Michigan)
Using improved estimates of Gaia photometry, dust extinction and distances for metal poor stars, we use empirical and well-defined relationships to get better estimates of effective temperature (Teff) and surface gravity (logg) values for 313 metal-poor stars. These estimates are important for calculating abundances in the stellar atmospheres and stellar metallicities.
Yanbo Pan, Eric Bell, Benjamin Radmore (University of Michigan)
By analyzing the stellar spatial distribution, we try to search for potential dwarf satellite galaxies by examining stellar overdensities within the DELVE survey. We attempt to search for overdensities for horizontal branch stars and red giant branch stars using the Density-Based Spatial Clustering of Applications with Noise (DBSCAN). We have focused on the Pegasus IV dwarf galaxy and its stellar population properties as a guide for our overdensity search. With the detected overdensities on the color-magnitude diagram, we also explore the stellar overdensities regarding their spatial distribution.
Em Peplinski (University of Michigan), Thomas Kennedy (University of Michigan), Emily Rauscher (University of Michigan)
The launch of JWST in late 2021 has made possible a new era of exoplanet research. Capable of incredibly sensitive infrared spectroscopy, the telescope enables examination of these distant planets’ atmospheres in greater detail than ever before. This allows us to learn about planet formation histories, common planet features, and to probe the question: are we alone in the Universe? It is our goal to study the structures and elements of these atmospheres through the comparison of our 3D exoplanet models to actual JWST observations. This poster details the method I have devised for taking the raw emission spectra from our models and turning them into simulated JWST spectra, processed in part using the program PandExo. In subsequent research, I will be making a tutorial of this method for use by the broader research group. We will also use this method to compare models of the Hot Jupiter WASP-80b to real JWST observations.
Benjamin C. Radmore (University of Michigan), Eric F. Bell (University of Michigan), Yanbo Pan (University of Michigan)
Ultra-faint dwarf galaxies (UFDs) are faint, dark matter-dominated galaxies comprised of notably low-metallicity stars. In this work, we reproduce the detection of Pegasus V, a dwarf satellite of M31, using data drawn from the DECaLS survey. We locate the galaxy as an overdensity in RGB/HB sources, and compare the CMD of said sources to the RGB/HB branch of a low-metallicity isochrone. We conclude that DECaLS is an effective tool for UFD detection, and intend to use it for further field scans.
Evan T. Rootness (University of Michigan), Eric F. Bell (University of Michigan), Jiaming Pan (University of Michigan)
Globular star clusters (GCs) are useful tools for studying hierarchical accretion models of galaxy formation and evolution because they are old, bright, and often numerous in large galaxies. The Andromeda Galaxy (M31) has already been searched thoroughly for GCs within a 150 kpc projected radius with the PAndAS survey. We aimed to extend this search past 150 kpc with the use of archival survey data from Pan-STARRS, WISE, and Gaia. We tuned our selection criteria to account for multiple parameters including color, size, and extended natures using a set of confirmed halo GCs. Within a 150 kpc radius we recovered 111 confirmed GCs, 77 of which were not included in the confirmed sample, with less than 2% contamination. When we applied the selection criteria past a radius of 150 kpc almost 200 candidates were selected. The candidates in the southwest region were contaminated with background galaxies, likely the result of the Perseus-Pisces supercluster overlapping with the search area. Additionally, the Galactic plane caused northern regions to be contaminated with tens of foreground stars. There were around 7 remaining ambiguous candidates that require follow up imaging or spectra to confirm or deny their classifications. Our aim is to take spectra of these remaining candidates and either disprove that there are bright GCs past 150 kpc, or discover the most distant GC from M31.
Alyssa Russell (University of Michigan), Leandro Beraldo e Silva (University of Michigan)
Grace Smith (University of Michigan), Guillaume Mahler (Durham University), Kate Napier (University of Michigan), Keren Sharon (University of Michigan), Matthew Bayliss (University of Cincinnati), Maxwell Klein (University of Michigan), Nicole Kuchta (University of Michigan), Ryan Walker (University of Michigan)
We present a strong lensing analysis and reconstruct the mass distribution of SPT-CL J0356−5337, a galaxy cluster at redshift z = 1.0359. This cluster was previously modeled by Mahler et al. (2020) using ground based imaging and spectroscopy, and single-band Hubble Space Telescope (HST) imaging. Using new multi-band HST data, we identify four additional lensed galaxies to inform a more well-constrained model using 14 sets of multiple images in 7 separate lensed sources. The three previously-known sources were spectroscopically confirmed by Mahler et al. (2020) at redshifts of z = 2.363, z = 2.364, and z = 3.048. Redshifts of two of the newly-discovered arcs were measured using archival MUSE data, at z = 3.0205 and z = 5.3288. Our model corroborates the conclusion that SPT-CL J0356−5337 is dominated by 2 mass components, and is likely undergoing a merger on the plane of the sky. Our lens model will be used in conjunction with X-ray data from Chandra to study the dynamical state of this system and determine whether it is pre- or post-merger; it will potentially confirm the highest redshift bullet-cluster-like example of a dissociative merger.
Sophia Troshynski (University of Michigan), M.S. Oey (University of Michigan), Norberto Castro (Leibniz Institute for Astrophysics Potsdam (AIP))
Benjamin Velguth (University of Michigan), Eric Bell (University of Michigan), Adam Smercina (University of Washington)
Ultra-diffuse galaxies (UDGs) are a relatively new classification of dwarf galaxies, characterized by low stellar mass (<10^8 M_sun) high radii (>2 kpc), and low surface brightness (~25 mag/arcsec^2). These galaxies have been observed throughout the universe, and understanding how they form is critical to filling a gap in our knowledge of galactic evolution. Up until now, these galaxies have only been studied as a population, but the proximity of F8D1 allows us to analyze the stellar populations within this UDG to understand the inner workings of these galaxies. Recently, (Žemaitis, et. al. 2022) discovered that F8D1 has been tidally disrupted, estimating a tidal radius of around 60 kpc. By analyzing the stellar population and star-formation history (SFH) of this tidal stream, we can conclude the likely formation mechanisms that took place within this galaxy and possibly generalize this formation to other UDGs in the universe. By using an SFH predicting method outlined in (Harmsen, et. al. 2023), we have been able to calculate that 90% of the star formation within F8D1’s tidal tail stopped 2.05 +/- 1.4 Gyr ago.