Bulletin of the American Physical Society
2021 Virtual Conference for Undergraduate Women in Physics
Friday–Sunday, January 22–24, 2021; Virtual
Session U13: Astrophysics and Cosmology VIIInteractive Live
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Chair: Benjamin Lehmann, UC Santa Cruz |
Sunday, January 24, 2021 12:00PM - 12:10PM |
U13.00001: Dark matter and electrons in the early Universe Dimple Sarnaaik, David Nguyen, Vera Gluscevic We explore the possibility of dark matter and electron interactions in the early Universe using the temperature, polarization, and lensing anisotropy of Planck measurements. No evidence of such interactions was found and thus we report an upper bound for the cross section of these interactions if they exist. We analytically estimated the upper limits of cross-sections for electron-dark matter particle interactions. This gave us an approximate idea of where the upper limits of these interactions lie, allowing us to accurately sample over that region of parameter space.We tested dark matter masses between 1 keV- 1 TeV with Monte Carlo Markov Chain (MCMC) analysis using Cobaya, a framework for sampling and statistical modeling. We compared our results with those for dark matter and proton interaction cross sections and found that dark matter masses of around 1MeV and lower have a tighter bound in electrons than protons. This is not true for higher mass ranges. Our results provide stronger constraints for dark matter particles by orders of magnitude. [Preview Abstract] |
Sunday, January 24, 2021 12:10PM - 12:20PM |
U13.00002: Studying the influence of bars on the $M$–$\sigma$ correlation Tanvi Deshmukh, Monica Valluri To examine the evolution of galaxies and their supermassive black holes, we look at the relationship between black hole mass, $M$, and the central velocity dispersion of stars, $\sigma$, commonly referred to as the $M$–$\sigma$ correlation. Using data from the cosmological TNG100 simulation, we compare the results of the most popular $\sigma$ calculation methods when applied to disk galaxies with varying bar strength. We also compare each $\sigma$ method to the kinetic energy of the stars in the central bulge and make the recommendation that $\sigma$ measurements which consider both line-of-sight dispersion and mean line-of-sight velocity get closest to accurately representing the galaxy. From here, we move on to analyzing $M$–$\sigma$ and find that TNG100 systematically overestimates $M$ when compared to observational data. However, we can still note differences between barred and unbarred galaxies, indicating that a more accurate relation can be obtained after separating galaxies by bar strength. Finally, we examine $M$–$\sigma$ for samples at increasing redshifts, $z$, and find that they differ from the correlation at $z=0$. This implies that if TNG100 represents reality, the $M$–$\sigma$ relationship in disk galaxies at $z=0$ cannot be used to predict $M$ at higher redshifts. [Preview Abstract] |
Sunday, January 24, 2021 12:20PM - 12:30PM |
U13.00003: Cosmological evolution of ultralight axionlike scalar fields Cameron Norton, Robert Scherrer We examine the cosmological evolution of ultralight axionlike (ULA) scalar fields with potentials of the form $V(\phi) = m^2 f^2[1 - \cos(\phi/f)]^n$, with particular emphasis on the deviation in their behavior from the corresponding small$-\phi$ power-law approximations to these potentials: $V(\phi) \propto \phi^{2n}$. We show that in the slow-roll regime, when $\dot \phi^2/2 \ll V(\phi)$, the full ULA potentials yield a more interesting range of possibilities for quintessence than do the corresponding power law approximations. For rapidly oscillating scalar fields, we derive the equation of state parameter and oscillation frequency for the ULA potentials and show how they deviate from the corresponding power-law values. We derive an analytic expression for the equation of state parameter that better approximates the ULA value than does the pure power-law approximation. [Preview Abstract] |
Sunday, January 24, 2021 12:30PM - 12:40PM |
U13.00004: Modified Gravity and the Black Hole Mass Gap Maria Straight, Jeremy Sakstein, Eric Baxter Modified gravity theories seek to explain dark energy and the observed expansion of the universe. These theories predict fifth forces that alter the structure and evolution of population-III stars. Because massive population-III stars experience pair-instability that can cause them to explode in a supernova that does not leave behind a black hole, theory predicts a gap in the distribution of astrophysical black hole masses. We find that increasing the strength of gravity exacerbates the pair-instability and changes the location of this black hole mass gap. We pioneer the black hole mass gap as a probe for modified gravity theories in a novel test of the strong equivalence principle where we apply our results to an analysis of the first ten LIGO/Virgo binary black hole merger events to obtain a $7\%$ bound on the gravitational constant experienced by baryonic matter relative to that experienced by black holes. The recently detected GW190521 event of two black holes with masses within the canonical mass gap can be explained by modified gravity if the black holes formed in a galaxy where the value of the gravitational constant is either enhanced or reduced by $\sim30\%$. [Preview Abstract] |
Sunday, January 24, 2021 12:40PM - 12:50PM |
U13.00005: Developing a Transient Identification Pipeline for DESI Using Machine Learning Amanda Wasserman, Vashisth Tiwari, Segev BenZvi Over the next five years, the Dark Energy Spectroscopic Instrument (DESI) will carry out a massive redshift survey of 35 million galaxies and quasars, mapping the large scale structure of the universe out to a redshift of 3. During the DESI survey we expect to find galaxies that host bright transients such as supernovae, tidal disruption events (TDEs), and compact binary mergers. The identification of transients is important not only to ensure correct estimates of the host redshifts, but also because it provides an opportunity to obtain serendipitous spectra of the transients themselves. Spectroscopic classification is the “gold standard” in the categorization of transients, making these discoveries invaluable when combined with data from large photometric surveys. We have developed machine learning tools to identify and classify transients in galaxy spectra. In this contribution we describe these tools, characterize their performance using simulated spectra, and estimate the sensitivity of DESI to transients important for both astrophysics and cosmology. [Preview Abstract] |
Sunday, January 24, 2021 12:50PM - 1:00PM |
U13.00006: Spectroscopic Analysis of Near-Chandrasekhar-Mass Type Ia Supernovae from the Double-Degenerate Channel Mckenzie Ferrari, Sudarshan Neopane, Khanak Bhargava, Niranjan Roy, Robert Fisher, Shin'ichirou Yoshida, Silvia Toonen Type Ia supernovae (SNe Ia) are the result of the explosion of white dwarfs (WDs) and inform the rate of acceleration of the universe, provide clues into the origin of elements crucial for life on Earth, and ultimately power the interstellar turbulence responsible for the birth of new stars. The canonical single-degenerate channel, consisting of a WD rapidly accreting from a non-degenerate star, has previously been believed to explain the origin of near-Chandrasekhar SNe Ia. However, in this work we suggest that the merger of two white dwarfs through the double-degenerate channel is instead the origin for the majority of near-Chandrasekhar mass SNe Ia. I will present synthetic spectra from hydrodynamical models of these SNe Ia, which are compared against past observed events to identify the sub-type of SNe and serve as crucial verification tests of the simulations. [Preview Abstract] |
Sunday, January 24, 2021 1:00PM - 1:10PM |
U13.00007: DES14C1kia: A Well-Observed Tidal Disruption Event Jessica Johnson, Tiara Hung, Ryan Foley When a star comes within a critical range of a black hole, the star is torn apart by tidal forces. These events, known as tidal disruption events (TDEs), present a unique opportunity to study quiescent black holes and their accretion mechanisms. Although the discovery of these events are becoming more common, it is rare to have early time data for TDEs. We present the data of DES14C1kia in optical from the Dark Energy Survey and in UV from the Swift Space Telescope. Of the 2,000 transient events observed by the Dark Energy Survey, this is the only TDE in its discoveries. DES14C1kia has a redshift of 0.162 and its light curve shows that it rises over a 56 day period to a peak absolute magnitude of $M_{g}$ = -18.8. Our results from MOSFiT, the Modular Open Source Fitter for Transients, determine this event is associated with a 20 million solar mass black hole and a 0.56 solar mass star that was disrupted. DES14C1kia is one of a handful of TDEs with multi-wavelength observations covering the entire pre-peak phase. The well-sampled light curves and its unique properties make DES14C1kia a valuable sample to add to the population of known TDEs. [Preview Abstract] |
Sunday, January 24, 2021 1:10PM - 1:20PM |
U13.00008: Automated stellar variability classification using TESS light curves Emma Chickles, Tansu Daylan, Lindsey Gordon Stellar variability has classically been divided into extrinsic sources (such as eclipses and rotation) and intrinsic sources (such as flares and pulsations). We conduct a census of different types of stellar variability using 2-minute cadence photometric light curves observed in the two-year mission of the Transiting Exoplanet Survey Satellite (TESS). We use an unsupervised artificial neural network and feature engineering to generate compressed, low-dimensional representations of the data. We apply clustering algorithms to the learned representations to perform large scale classification of stellar variability in TESS light curves. We validate our pipeline using the General Catalogue of Variable Stars, which contains 54,821 stars primarily in the Milky Way galaxy. The large scale survey produced by TESS offers an opportunity to calculate statistical descriptions of properties, such as type, age, metallicity, and mass, of different variability types. Our homogeneous census of stellar variability will lead to a better understanding of the underlying demographics. [Preview Abstract] |
Sunday, January 24, 2021 1:20PM - 1:30PM |
U13.00009: Predictions for the Infall Pattern near Large-scale Cosmological Filaments Jesse Kelley-Derzon, Lucas Graham, Mary Crone Odekon, Jake Rabinowitz, Isaac Ngunje, Evan Halstead, Mike Jones We present a method for estimating the amount of matter in large-scale (\textasciitilde 50 Mpc) filaments using the surrounding velocity infall pattern, based on 242 filaments in the Millennium simulation. We identify filaments using a minimal spanning tree to link large groups and clusters, and find the axis of each filament using a weighted principal component analysis. We improve our previous determination of a typical infall velocity profile by rescaling the profile for each filament by the distance where the infall speed reaches a maximum. We use the resulting average profile to determine a two-parameter piecewise function that can be used to estimate the maximum infall speed and the mass of the filament. These results will be used as part of the Arecibo Pisces-Perseus Supercluster filament. This work is supported by NSF grant AST-1637339. [Preview Abstract] |
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