Bulletin of the American Physical Society
Annual Meeting of the APS Four Corners Section
Volume 60, Number 11
Friday–Saturday, October 16–17, 2015; Tempe, Arizona
Session I3: Cosmology II |
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Chair: Ceclila Lunardini, Arizona State University Room: PSF123 |
Saturday, October 17, 2015 11:00AM - 11:12AM |
I3.00001: Characterization of Cosmic Dawn through Observations of the Redshifted 21-cm Line Raul Monsalve, Judd Bowman, Thomas Mozdzen, Alan Rogers One way of tracking the formation of the first generations of compact objects in the Universe during the period of Cosmic Dawn (40 $>$ z $>$ 6) is through observations of the 21-cm line emitted by neutral atomic hydrogen (HI) in the intergalactic medium due to the hyperfine splitting of its ground state. Models have been developed for this observable and precise estimation of their parameters would allow constraining the fundamental physics of structure formation in the early Universe. The cosmological HI signal was emitted at $\sim$ 1.4 GHz but its detection is expected in the VHF range (between 40 and 200 MHz) due to cosmic expansion. The models suggest that the signal is extremely weak, about four orders of magnitude weaker than the relevant foregrounds, making its detection a daunting endeavor. This talk will describe EDGES (\emph{Experiment to Detect the Global EoR Signature}), an instrument developed by Arizona State University and MIT currently operating in the desert of Western Australia. It attempts to detect the large-scale HI signal from Cosmic Dawn following a single-antenna approach and relying on extremely accurate calibration. The talk will present data recently taken, will describe the processing pipeline, and will discuss the status of the science analysis. [Preview Abstract] |
Saturday, October 17, 2015 11:12AM - 11:24AM |
I3.00002: Instrumental Effects on 1-Point Statistics in Redshifted 21 cm Observations Piyanat Kittiwisit, Judd Bowman, Daniel Jacobs, Nithyanandan Thyagarajan, Adam Beardsley We study the impact of instrumental systematics on the 1-point statistics of redshifted 21-cm signal from reionization via data-driven simulations. We simulate realistic 21-cm observations based on the Murchison Widefield Array (MWA) reionization experiment, incorporating full-sky semi-analytic 21-cm models, phased-array antenna beam response, and an existing MWA imaging pipeline. The simulations produce 2-second driftscan snapshots of 21-cm intensity maps, spanning across redshift 6 to 9, as seen by the MWA. Previous studies suggest that the pixel probability density function (PDF) and higher-order statistics in the theoretical 21-cm maps should exhibit non-Gaussian features. Our results show that the instrumental beam response strongly corrupts these features. The shortest antenna pairs in the array that sample one-degree scales influence the shape of the PDF the most by smoothing out non-Gaussian features in the smaller scales. Sidelobe confusion further masks out non-Gaussian features by adding noise-like structures to the maps. Nevertheless, the features can still be seen as a positive skewness toward the end of reionization when the theoretical 21-cm PDF becomes highly bi-modal. [Preview Abstract] |
Saturday, October 17, 2015 11:24AM - 11:36AM |
I3.00003: Emission Line Science in the Faint Infrared Grism Survey (FIGS) Sample Mark Smith, Sangeeta Malhotra, James Rhoads, John Pharo Emission lines can reveal a bounty of information about the processes occurring within a galaxy. Physical properties such as star formation rate and metallicity can be determined from ratios of emission line fluxes. The study of emission line galaxies (ELGs) through cosmic time gives insight into the processes by which galaxies evolve. Extreme emission line galaxies (EELGs), typified by strong nebular emission lines which dominate their spectra, are of interest because they are well known to be galaxies undergoing periods of intense star formation. Slitless spectroscopy offers a significant advantage to the study of ELGs and EELGs, allowing for measurement of the spectra of a large number of galaxies within a field. This allows for detection of ELGs and EELGs with few selection biases, and analysis of the emission lines present without the need for time-consuming individual follow-up. In this talk I will introduce the physics governing the two types of nebular emission lines, recombination lines and forbidden lines, and describe the environments in which these emission lines are generated. I will discuss the methods used to identify and analyze ELGs in FIGS and what has been learned so far. I will also explore applications to the Wide Field InfraRed Survey Telescope (WFIRST). [Preview Abstract] |
Saturday, October 17, 2015 11:36AM - 11:48AM |
I3.00004: Gravitons to Photons -- attenuation of gravitational waves Preston Jones In the International Gravity Essay Contest for 2015 we examine the Fulling-Davies-Unruh detector response to a gravitational wave background. The spectrum of the Unruh-Dewitt radiation is of the same form as some scattering processes or three body decays such as muon-electron scattering or muon decay. Based on this similarity we propose that the Fulling-Davies-Unruh detector response implies an attenuation of the gravitational wave through production of photons. Over large distances this attenuation may have consequences for the detection of gravitational waves. [Preview Abstract] |
Saturday, October 17, 2015 11:48AM - 12:00PM |
I3.00005: Biconformal Gauge Theory: A New Perspective on the Coleman-Mandula Theorem Benjamin Lovelady, James Wheeler The four fundamental interactions can be understood as gauge theories of Lie groups. According to the Coleman-Mandula Theorem, the only way to combine spacetime and internal symmetry groups, i.e. gravity and one or more of the other interactions, is by a direct product. Most theories circumvent this by extending the Lie Groups to Lie Supergroups. We take a different approach, showing that it is possible to construct a gauge theory of a simple Lie group that dynamically requires subgroups of Lorentz and Euclidean signature, i.e. spacetime and internal symmetries. These subgroups are combined by a direct product, as the Coleman-Mandula Theorem requires. We consider both the flat case, and cases perturbative in the curvature. [Preview Abstract] |
Saturday, October 17, 2015 12:00PM - 12:12PM |
I3.00006: Dark Matter and Neutron Stars: A Match Made in Heaven Pedro Luis Espino, Ina Sarcevic Neutron Stars offer the perfect environment for testing Dark Matter models. Because of its compact nature, a Neutron Star within a distribution of Dark Matter (DM) can collect DM particles near its core. Once this collected number density exceeds a critical limit, gravitational collapse of the collected DM may cause a black hole to form at the center of the star, in turn destroying the star the from within. The number and age of observed Neutron Stars within a given distribution of DM can be used to put constraints on the parameter space of Dark Matter models. Strongly motivated Particle Dark Matter models are reviewed and tested in the context of Neutron Stars, and limits are placed on parameter space. The study of Dark Matter in the context of Neutron Stars offers a good way of constraining otherwise un-testable models, and may be related to other astrophysical problems, such as the missing pulsar problem. [Preview Abstract] |
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