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dc.contributor.advisorEisenstein, Daniel J.en_US
dc.contributor.authorMehta, Kushal Tushar
dc.creatorMehta, Kushal Tusharen_US
dc.date.accessioned2014-08-26T20:37:48Z
dc.date.available2014-08-26T20:37:48Z
dc.date.issued2014
dc.identifier.urihttp://hdl.handle.net/10150/325226
dc.description.abstractBaryon acoustic oscillations (BAOs) are used to obtain precision measurements of cosmological parameters from large-scale surveys. While robust against most systematics, there are certain theoretical uncertainties that can affect BAO and galaxy clustering measurements. In this thesis I use data from the Sloan Digital Sky Survey (SDSS) to measure cosmological parameters and use N-body and smoothed-particle hydrodynamic (SPH) simulations to measure the effect of theoretical uncertainties by using halo occupation distributions (HODs). I investigate the effect of galaxy bias on BAO measurements by creating mock galaxy catalogs from large N -body simulations at z = 1. I find that there is no additional shift in the acoustic scale (0.10% ± 0.10%) for the less biased HODs (b < 3) and a mild shift (0.79% ± 0.31%) for the highly biased HODs (b > 3). I present the methodology and implementation of the simple one-step reconstruction technique introduced by Eisenstein et al. (2007) to biased tracers in N-body simulation. Reconstruction reduces the errorbars on the acoustic scale measurement by a factor of 1.5 - 2, and removes any additional shift due to galaxy bias for all HODs (0.07% ± 0.15%). Padmanabhan et al. (2012) and Xu et al. (2012) use this reconstruction technique in the SDSS DR7 data to measure Dᵥ(z = 0.35)(rᶠⁱᵈs/rs) = 1356 ± 25 Mpc. Here I use this measurement in combination with measurements from the cosmic microwave background and the supernovae legacy survey to measure various cosmological parameters. I find the data consistent with the ΛCDM Universe with a flat geometry. In particular, I measure H₀ = 69.8 ± 1.2 km/s/Mpc, w = 0.97 ± 0.17, Ωk = -0.004 ± 0.005 in the ΛCDM, wCDM, and oCDM models respectively. Next, I measure the effect of large-scale (5 Mpc) halo environment density on the HOD by using an SPH simulation at z = 0, 0.35, 0.5, 0.75, 1.0. I do not find any significant dependence of the HOD on the halo environment density for different galaxy mass thresholds, red and blue galaxies, and at different redshifts. I use the MultiDark N-body simualtion to measure the possible effect of environment density on the galaxy correlation function ℰ(r). I find that environment density enhances ℰ(r) by ∽ 3% at scales of 1 – 20h⁻¹Mpc at z = 0 and up to ∽ 12% at 0.3h⁻¹Mpc and ∽ 8% at 1 - 4h⁻¹Mpc for z = 1.
dc.language.isoen_USen
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.subjectLarge-scale structureen_US
dc.subjectAstronomyen_US
dc.subjectCosmologyen_US
dc.titleMeasuring the Universe with High-Precision Large-Scale Structureen_US
dc.typetexten
dc.typeElectronic Dissertationen
thesis.degree.grantorUniversity of Arizonaen_US
thesis.degree.leveldoctoralen_US
dc.contributor.committeememberEisenstein, Daniel J.en_US
dc.contributor.committeememberPinto, Philipen_US
dc.contributor.committeememberZaritsky, Dennisen_US
dc.contributor.committeememberWalker, Christopheren_US
dc.contributor.committeememberOlszewski, Edwarden_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineAstronomyen_US
thesis.degree.namePh.D.en_US
refterms.dateFOA2018-08-14T06:32:59Z
html.description.abstractBaryon acoustic oscillations (BAOs) are used to obtain precision measurements of cosmological parameters from large-scale surveys. While robust against most systematics, there are certain theoretical uncertainties that can affect BAO and galaxy clustering measurements. In this thesis I use data from the Sloan Digital Sky Survey (SDSS) to measure cosmological parameters and use N-body and smoothed-particle hydrodynamic (SPH) simulations to measure the effect of theoretical uncertainties by using halo occupation distributions (HODs). I investigate the effect of galaxy bias on BAO measurements by creating mock galaxy catalogs from large N -body simulations at z = 1. I find that there is no additional shift in the acoustic scale (0.10% ± 0.10%) for the less biased HODs (b < 3) and a mild shift (0.79% ± 0.31%) for the highly biased HODs (b > 3). I present the methodology and implementation of the simple one-step reconstruction technique introduced by Eisenstein et al. (2007) to biased tracers in N-body simulation. Reconstruction reduces the errorbars on the acoustic scale measurement by a factor of 1.5 - 2, and removes any additional shift due to galaxy bias for all HODs (0.07% ± 0.15%). Padmanabhan et al. (2012) and Xu et al. (2012) use this reconstruction technique in the SDSS DR7 data to measure Dᵥ(z = 0.35)(rᶠⁱᵈs/rs) = 1356 ± 25 Mpc. Here I use this measurement in combination with measurements from the cosmic microwave background and the supernovae legacy survey to measure various cosmological parameters. I find the data consistent with the ΛCDM Universe with a flat geometry. In particular, I measure H₀ = 69.8 ± 1.2 km/s/Mpc, w = 0.97 ± 0.17, Ωk = -0.004 ± 0.005 in the ΛCDM, wCDM, and oCDM models respectively. Next, I measure the effect of large-scale (5 Mpc) halo environment density on the HOD by using an SPH simulation at z = 0, 0.35, 0.5, 0.75, 1.0. I do not find any significant dependence of the HOD on the halo environment density for different galaxy mass thresholds, red and blue galaxies, and at different redshifts. I use the MultiDark N-body simualtion to measure the possible effect of environment density on the galaxy correlation function ℰ(r). I find that environment density enhances ℰ(r) by ∽ 3% at scales of 1 – 20h⁻¹Mpc at z = 0 and up to ∽ 12% at 0.3h⁻¹Mpc and ∽ 8% at 1 - 4h⁻¹Mpc for z = 1.


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