Bulletin of the American Physical Society
2021 Virtual Conference for Undergraduate Women in Physics
Friday–Sunday, January 22–24, 2021; Virtual
Session U10: Astrophysics and Cosmology IVInteractive Live
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Chair: Molly Watts, Columbia Univ |
Sunday, January 24, 2021 12:00PM - 12:10PM |
U10.00001: Nonlinear Dynamics from Early Dark Energy Ericka Florio, Mary Gerhardinger, Tom Giblin The Hubble tension, one of the foremost problems in contemporary cosmology, describes the disparity between two independent ways of measuring the current expansion rate of the Universe, called the Hubble constant. The Hubble tension now stands at 4.2$\sigma$, which is a strong indicator of unknown physics. The Early Dark Energy (EDE) field is a scalar field which would have begun to oscillate around matter-radiation equality and would have decayed away quickly afterwards, giving the expansion of the Universe a "boost" at that time which might resolve the Hubble tension (Poulin et al. 2019). The EDE field also displays nonlinear behavior as it decays, behavior which could lead to possible predictions of the EDE theory. However, since the EDE field has so far only been studied using linear analysis, this behavior is not well understood. We are simulating the Universe with EDE added in using GABE, a 3+1-d code which numerically simulates an expanding Universe alongside scalar fields and fluids in the presence of local gravity. It is specifically designed to study nonlinear dynamics. With these simulations, we can determine whether the nonlinear behavior of the EDE field would produce observable consequences, which could then be searched for using next-generation CMB telescope. [Preview Abstract] |
Sunday, January 24, 2021 12:10PM - 12:20PM |
U10.00002: Extracting Radial Velocities of Cool, Low Mass Stars Using Forward Modeling with PARVI Katelyn Horstman Observations have shown exoplanets are abundant around type K \& M stars. To search for companions around these cooler, low mass stars, we benefit from observing targets in near infrared (NIR) wavelengths (758 -1388 nm) where the star has its peak emission. We use observations from the Palomar Radial Velocity Instrument (PARVI) to measure radial velocities of type K \& M stars. We present an addition to the existing data reduction pipeline created for PARVI that obtains stellar radial velocities from the one-dimensional spectra of the object. Using a forward modeling technique, we create a model spectrum to mimic the reduced spectrum taken from instrument observations. We focus on four factors when creating our model: a stellar template represented by high resolution PHOENIX models, the telluric absorption of the atmosphere, the blaze function, and line broadening. We apply our radial velocity data reduction pipeline to observations of GJ229 A and recover an estimated, best precision of 11 m/s. Our results are a first step toward showing PARVI can obtain the dynamical masses of candidate planets orbiting K \& M stars detected by the NASA TESS mission. [Preview Abstract] |
Sunday, January 24, 2021 12:20PM - 12:30PM |
U10.00003: Reconciling different expressions for the pulsar timing residuals induced by single-source gravitational waves Hyo Sun Park, Andrea Lommen Pulsars are fast-spinning neutron stars that send electromagnetic pulses to Earth at regular intervals. The times of arrival (TOAs) of their pulses vary when gravitational waves (GWs) pass through, as GWs stretch and shrink the spacetime between the pulsars and the Earth. Pulsar Timing Arrays (PTAs) can directly detect individual GW sources by measuring the timing ``residual,'' the difference between the observed TOAs and the expected TOAs. Due to their high sensitivity in the nano-Hz band, PTAs are the primary GW detector for supermassive black hole binaries (SMBHBs). Many authors have derived the expression for the timing residuals induced by a GW emitted from a SMBHB in a circular orbit. However, we find that there are discrepancies in the published equations, and the notations and coordinate systems being used vary considerably among the authors. We trace their references back to the 1975 and 1989 documents and derive the timing residuals directly using the equations in these original references. We describe how to do conversions between the published expressions and attempt to correct the inconsistencies between them. We also point out the misunderstanding of the ``Earth term'' in timing residuals having the same phase across all the pulsars. [Preview Abstract] |
Sunday, January 24, 2021 12:30PM - 12:40PM |
U10.00004: Investigation of Instabilities in the Magnetosphere Elizabeth Wraback, Surjalal Sharma, Jason Shuster The Magnetospheric Multiscale Mission (MMS) uses four identical spacecraft orbiting the Earth in the magnetosphere to observe the microphysics of magnetic reconnection, particle acceleration, and turbulence. On 12/30/2015, within a 10-minute period of low ion density, there were a series of three 30-second peaks in the ion density and related structures in the ion temperature, ion velocity, and electron energy. In this presentation, I will discuss the analysis of the first density structure. By performing timing analyses and calculating the current density and the plasma parameters for this event, the density increase appears to be the product of magnetic reconnection. Future work is needed to determine whether the other two density structures are associated with magnetopause reconnection events and how these three structures are related. [Preview Abstract] |
Sunday, January 24, 2021 12:40PM - 12:50PM |
U10.00005: Combined Energy Spectrum of the Supernova Remnant IC 443 Leah Hunt, Miguel Mostafa The supernova remnant IC 443 is a very well-studied source and a clear example of interaction with a molecular cloud. We consider the highest energy emissions of the source using data collected with the High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory. We combine the TeV data from HAWC with radio, X-ray, and gamma-ray data from other experiments in order to produce a physical model including both leptonic and hadronic emission. [Preview Abstract] |
Sunday, January 24, 2021 12:50PM - 1:00PM |
U10.00006: X-ray Follow-Up to Dark Energy Survey Year 3 Galaxy Clusters Allison Swart Dark energy has important implications for the history and future of our universe, but not much of its nature is understood. One way to place constraints on the dark energy equation of state is to examine the properties of galaxy clusters, which can be done by large-scale surveys and related follow-ups. In this research, I performed an X-ray follow-up to galaxy clusters selected optically by the Dark Energy Survey. X-ray follow-ups offer a check on aspects of optical cluster selection such as centering and help calibrate cluster mass through mass proxies like X-ray temperature and luminosity. During analysis, I identified remarkable cluster components such as center galaxies and cluster mergers and performed checks on the X-ray analysis pipeline MATCha (Mass Analysis Tool for Chandra) in contribution to the constraint of dark energy. [Preview Abstract] |
Sunday, January 24, 2021 1:00PM - 1:10PM |
U10.00007: The Hubble Tension and Early Dark Energy: Studying Nonlinear Instabilities Mary Gerhardinger, Ericka Florio, John Giblin One of the emerging problems within cosmology today is the tension between separate measurements of the Hubble constant ($\text{H}_0$), the rate of the expansion of the Universe today. This discrepancy could be due either to systematic errors in measurements or an incompleteness in the Lambda-CDM model of Cosmology. In this work, we assume the latter and investigate a possible solution to this tension by introducing a scalar field, called Early Dark Energy (EDE). EDE ‘turns on’ around matter-radiation equality, coherently oscillates, and changes the expansion of the universe (Poulin et al 2018). In order to affect only one early-time measurement of H0, it also needs to dilute away quickly which is achieved through nonlinear dynamics. Using only linear analysis, EDE has been shown to solve the Hubble Tension, however nonlinear physics is present which should additionally have observational consequences. Hence, we study the dynamics of this field using a code entitled GABE which numerically evolves scalar fields and fluids in an expanding universe with local gravity. Our goal is to simulate a universe with EDE present in order to make observational predictions about what our Universe should look like today if it had EDE in it. [Preview Abstract] |
Sunday, January 24, 2021 1:10PM - 1:20PM |
U10.00008: Simulating Observations of M87 with the Event Horizon Telescope and Space VLBI Catherine Petretti, Vincent Fish, Kazunori Akiyama The Event Horizon Telescope (EHT), composed of many sub-millimeter radio telescopes across the globe, uses Very-Long-Baseline Interferometry to act as a telescope the size of the Earth. In 2019, the EHT released the first image of a black hole, the super massive black hole at the center of M87. Such images have the potential to provide insight on highly distorted areas of space-time, the perfect environment to test General Relativity and to study the astrophysics of jet formation. However, the EHT's angular resolution of $\sim 20\ \mu as$ does not provide enough detail to resolve important features such as radiative outbursts surrounding the accretion disk, nor to measure the shape and position of the photon ring at physically interesting levels. Here we simulate observations of general relativistic magnetohydrodynamic models of the Kerr black hole M87 with the EHT in conjunction with various satellite arrays to demonstrate how the extension of the EHT into Earth orbit will benefit imaging. Arrays consisting of two satellites just above Geosynchronous Earth Orbit yield an angular resolution of $\sim 3\ \mu as$, providing sharper, more faithful images of M87 and demonstrating the ability to produce spatially resolved, time-resolved movies of the jet-launch region. [Preview Abstract] |
Sunday, January 24, 2021 1:20PM - 1:30PM |
U10.00009: Modeling the 3D Emission Spectra and Phase Curves of Hot Jupiter WASP-43b Nina Robbins Blanch, Tiffany Kataria, Natasha Batalha We calculate 3D spectra and phase-resolved emission for the hot Jupiter WASP-43b considering atmospheric dynamics and clouds by using a suite of atmospheric codes. We first use the 3D pressure, temperature and eddy diffusion profiles from the SPARC/MITgcm, a 3D general circulation model (GCM), as inputs to Virga, a phase equilibrium code that computes the optical depth and scattering properties of condensate clouds on hot Jupiters. With Virga, we calculate 3D cloud profiles with different sedimentation efficiencies. Together, we use WASP-43b's thermal structure and cloud properties to simulate spectra using PICASO, a radiative transfer code. We also compute cloud-free spectra for testing and comparison purposes. We will build upon the framework of PICASO by developing a function that calculates a planet's phase-resolved emission (i.e., phase curves) in thermal emission. In this way, we can compare our simulated phase curves of WASP-43b to observations from Spitzer and HST. Finally, we will make predictions for future phase-curve observations of WASP-43b using JWST. [Preview Abstract] |
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