Bulletin of the American Physical Society
2021 Virtual Conference for Undergraduate Women in Physics
Friday–Sunday, January 22–24, 2021; Virtual
Session U09: Astrophysics and Cosmology IIIInteractive Live
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Chair: Khushi Bhatt, Western Michigan University |
Sunday, January 24, 2021 12:00PM - 12:10PM |
U09.00001: Polarized Imaging for Reionization, with an Application to HERA Jennifer Locke, James Aguirre, Zachary Martinot, Jianrong Tan, Kaelyn Dauer, Adriana Gavidia, Alexander Seidel, Gonzalo Tucker A continuing source of uncertainty for Epoch of Reionization (EoR) measurements is the degree to which polarized foregrounds (and imperfect accounting of the polarized response of the instrument) will contaminate the measurement of the unpolarized EoR signal.~Measuring and characterizing polarized emission at low radio frequencies requires good models of the intrinsic polarized signal from extragalactic and Galactic sources, the rotation measure structure of the Galactic ISM, and others, combined with the ability incorporate all of these effects into fully-polarized visibility simulation and calibration. While HERA is not optimized for imaging, given the highly redundant array configuration, we have nevertheless made significant progress in modeling the full polarization response of the antenna and feed, and incorporating this into realistic simulations of the measured visibilities.~We discuss the current difficulties with models of source emission rotation measure, and how we have incorporated the ionosphere into our simulations.~We also discuss success thus far with a custom calibration approach. We explore correcting for the primary beam using both an image-based, least-squares solution for the Stokes images, as well as deconvolution using tools from CASA. [Preview Abstract] |
Sunday, January 24, 2021 12:10PM - 12:20PM |
U09.00002: HI Shielding of H$_{\mathrm{2}}$ in UV Irradiated Protogalaxies: Building the First Massive Black Holes Meredith Neyer, Jemma Wolcott-Green Observations of supermassive black holes in the early universe have necessitated new theories to explain the rapid formation and growth of early black holes. One of the most prominent of these theories is direct collapse, which suggests that suppressing molecular hydrogen (H$_{\mathrm{2}})$ abundance in protogalactic halos can cause inefficient H$_{\mathrm{2}}$ cooling leading to rapid accretion onto a dense core, forming a supermassive star, and ultimately a black hole. Since H$_{\mathrm{2}}$ is the primary cooling agent in primordial gas, a high UV flux can dissociate enough H$_{\mathrm{2}}$ to prevent the halo from cooling below the virial temperature. Simulations of these protogalaxies require precise modeling of chemical processes to determine the critical UV flux that will suppress enough H$_{\mathrm{2}}$ to keep the halo ``hot''. We use three-dimensional cosmological simulations to study a process not previously included: neutral atomic hydrogen (HI) shielding of H$_{\mathrm{2}}$ and its impact on the critical flux. HI can absorb some of the H$_{\mathrm{2}}$-dissociating UV radiation, and as a result, we find that the critical flux increases significantly when HI shielding is included. [Preview Abstract] |
Sunday, January 24, 2021 12:20PM - 12:30PM |
U09.00003: Effects of Eccentricity on Binary Black Hole Detection Rates by LIGO Urja Shah, Imre Bartos Templated based gravitational wave searches used by AdLIGO and AdVIRGO currently do not include eccentric orbital templates. I am working to find a rate of binary black hole mergers for not highly and highly eccentricities that LIGO could detect in the O5 observational run. To do this, I am reviewing all the potential theoretical models of binary systems including the environment that they are originating from. Along with the information for the theoretical models, the details about the detectors and their detection capacity plays a big role in predicting a detection rate for mergers by LIGO in O5. Using information provided in LIGO reference papers, we are able to obtain important equations and constants used in the calculations. The technique used to perform the calculations includes finding the detection rates for the past O2 run since the reference papers constants corresponds of the O2 run. These were then upscaled to the O5 run by taking into consideration the potential time that LIGO will be running as well as the range of distance it will be observable. I am presenting the detection rate prediction calculated for one such binary black hole model for the O5 run. [Preview Abstract] |
Sunday, January 24, 2021 12:30PM - 12:40PM |
U09.00004: Gravitational-Wave Signatures from Compact Object Binaries in the Galactic Center HUIYI WANG, Alexander Stephan, Smadar Naoz, Bao-Minh Hoang, Katelyn Breivik Almost every galaxy has a supermassive black hole (SMBH) residing at its center, the Milky Way included. Recent studies suggested that these unique places are expected to host a high abundance of stellar and compact object binaries. These binaries form hierarchical triple systems with the SMBH and undergo the eccentric Kozai-Lidov (EKL) mechanism. Here we estimate the detectability of potential Gravitational Wave (GW) emission from these compact objects within the frequency band of the Laser Interferometer Space Antenna (LISA) and Laser Interferometer Gravitational-Wave Observatory (LIGO). We generate a post EKL population of stars at the onset of Roche limit crossing and follow their evolution to compact object binaries. As a proof-of-concept, we adopt two metallicities, solar metallicity ($Z = 0.02$) and $15\%$ of it ($Z = 0.003$). We demonstrate that over the observation timescale of LISA, black hole binaries (BH-BH) and white dwarf binaries (WD-WD) provides the most prominent GW sources via the EKL assisted merger channel. Systems involving neutron stars (e.g., NS-BH, NS-NS) are less observable but possibly abundant through different merger channels. [Preview Abstract] |
Sunday, January 24, 2021 12:40PM - 12:50PM |
U09.00005: Forming Stars in W51 as Seen by ALMA Danielle Bovie W51 is a star forming giant molecular cloud. While comparing images taken of W51 North by ALMA at long and short baselines, I looked at not only possible protostars and their surrounding disks, but also the reservoir of gas and dust that surrounds them. This reservoir is the surrounding gas and dust that is accreting onto the star. By subtracting the different resolution images I was able to isolate the surrounding material and compare the flux in the low resolution image coming from the protostar and surrounding disk and the flux coming from the surrounding reservoir of material. By knowing how much material is in the surrounding reservoir we can gain insight into the protostar’s potential for future growth. [Preview Abstract] |
Sunday, January 24, 2021 12:50PM - 1:00PM |
U09.00006: An Asteroseismic Age for a Solar Type Star in a Wide Binary with an M dwarf Erica Sawczynec, Jennifer van Saders, Daniel Huber, Jason Curtis, Nicholas Saunders, John Tonry M dwarfs are popular targets for modern surveys as they are the most numerous and longest-lived stars in the universe. Their close habitable zones make them ideal candidates for finding exoplanets using typical planet-finding methods. Being able to estimate the ages of M dwarfs is crucial; young M dwarfs produce high energy flares which may affect the atmospheres of and the probability of finding bio-signatures on surrounding planets. However, estimating the ages of M dwarfs is challenging, and conventional techniques often fail. Some age-dating techniques, such as period-age relations, could be widely used, but require further calibration. The system HIP 43232, comprised of an M dwarf in a wide binary pair with a late F type star, can provide a benchmark for such calibration as ages of solar-like stars can be estimated using asteroseismology. Asteroseismology is the study of the oscillations in stars using the visible pulsations to determine stellar properties such as age, radius, and mass. Here we present the stellar parameters of the late F type star in HIP 43232 derived using asteroseismology utilizing data from the K2 survey. Additionally, we present the stellar parameters and rotation period of the M dwarf and their implications for testing M dwarf spin down. [Preview Abstract] |
Sunday, January 24, 2021 1:00PM - 1:10PM |
U09.00007: Determining the Efficiency of HETDEX's Emission Line Discovery Algorithm Delaney White, Steven Finkelstein, Adam McCarron, Dustin Davis, Oscar Chavez, Gene Leung, Daniel Mock The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) takes advantage of the Hobby-Eberly Telescope at McDonald Observatory to map the three-dimensional positions of more than a million galaxies and will ultimately revolutionize our understanding of dark energy. While HETDEX already has an algorithm for detecting emission lines, many in the collaboration believe this collection is incomplete and wish the results could be verified by a separate analysis. I created an automatic line-finding code using a Markov chain Monte Carlo Ensemble sampler to cipher through over 60,000 known galaxies in one of HETDEX's spectroscopic surveys. My results will verify HETDEX detections and characterize the efficiency of the HETDEX algorithm based on feature strength. By quantifying what features are missing, collaborators can then improve the HETDEX algorithm and potentially increase the detection rate. Furthermore, verifying the catalog of known detections would give scientists confidence that the features they study are real. [Preview Abstract] |
Sunday, January 24, 2021 1:10PM - 1:20PM |
U09.00008: Detecting the 21cm Signal from EoR using HERA Mine Gokcen Hydrogen Epoch of Reionization Array (HERA) is a radio telescope consisting of over 300 individual dishes with a collecting area of 150 square meters. It is the most sensitive radio telescope designed to measure the 21cm (HI) signal that characterises the Epoch of Reionization (EoR). The detection of HI signal is important to constrain the theoretical models of reionization and cosmic dawn. Parameters of these models -namely the star formation efficiency, circular velocity of star forming halos, and x-ray heating efficiency in the scope of this presentation- describe the formation of first stars and galaxies. By comparing the power spectra from simulations to the sensitivities of HERA, we determine the ranges of parameters that can be detected by HERA; thus, the extent to which HERA will contribute to our understanding of the cosmic history. [Preview Abstract] |
Sunday, January 24, 2021 1:20PM - 1:30PM |
U09.00009: The Circular Polarization of Galactic Synchrotron Emission Kassidy Kollmann, Tobias Marriage, Yunyang Li Studying the cosmic microwave background (CMB) is important for better understanding the origin and evolution of our Universe. However, the circular polarization (CP) of the CMB has not been well studied, as this signal is obscured by a more prominent source of CP due to Galactic synchrotron emission (GSE). This project set out to determine if the Cosmology Large Angular Scale Surveyor (CLASS) telescope, which aims to map the polarization pattern of the CMB, is sensitive enough to detect the expectedly weak GSE CP signal. For this project, we used a data-driven model of Galactic CP as a template to cross-correlate with CP data from CLASS. We ultimately concluded that CLASS is not currently sensitive enough to detect the CP from the GSE, however, we succeeded in producing upper limit estimates on the contribution of GSE CP to the CLASS maps. We determined the signal-to-noise ratio in the CLASS CP maps to be approximately 1/7. For a 5$\sigma$ detection of the GSE CP signal, we would need 35x less noise in the CLASS data, or equivalently, 1225x as much CLASS data if the GSE CP signal is as predicted by models. This is a preliminary dataset, and GSE CP constraints may be achievable with much larger data volumes that are currently being collected. [Preview Abstract] |
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