[PDF] Robust Measurements Of The Large Scale Clustering Of Galaxy Survey Data eBook

Author : Mehdi Rezaie
Publisher :
Page : 198 pages
File Size : 42,39 MB
Release : 2021
Category : Astronomical surveys
ISBN :

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Large-scale structure (LSS) of the Universe traced by galaxies is one of the essential probes of dark energy, dark matter, neutrino masses, nature of gravity, and statistical properties of primordial fluctuations. The clustering of primordial fluctuations from the cosmic microwave background to LSS provides a standard ruler test to study the dynamics of the cosmic expansion and the mysterious dark energy. Additionally, LSS can be utilized to reconstruct the primordial features and the statistical properties of the initial conditions of the Universe. Future galaxy redshift surveys are designed to extend aggressively to higher redshifts to reach a greater cosmic volume for improved precision as well as for studying the dynamics of dark energy further back in time. For instance, the Dark Energy Spectroscopic Instrument (DESI) will observe millions of galaxies and quasars, producing a three–dimensional map probing the Universe across 10 billion light-years or out to the redshift of 3.5. With enormous data volume, we can address fundamental cosmological problems with higher statistical precision, but such analyses demand more advanced methods and theoretical modeling of systematics. Emmission line galaxies (ELGs) are star-forming galaxies that populate the high redshift universe and therefore are promising tracers for LSS that will be targeted in future galaxy surveys. Quasi-stellar objects or quasars (QSOs) are distant galaxies that host massive black holes and the accreting black holes make these objects bright enough to be used as targets for high redshift galaxy surveys. However, the measurements of such targets are subject to various observational systematic effects that are still largely unknown. Mitigating such effects is crucial for deriving unbiased and precise cosmological constraints. This dissertation addresses the challenge of observational systematics by comparing the results of various approaches. My dissertation consists of three parts: In the first part, I establish a deep learning approach to model and mitigate the effects of observational systematics in the large-scale clustering of galaxies. I implement, validate, and apply the method to log-normal mock datasets as well as ELGs from real imaging data that will be used for targeting in DESI. I demonstrate that the nonlinear approach based on neural networks reduces observational systematics more efficiently than conventional linear regression. In the second part, I enhance the methodology for the final sample of quasars from the extended Baryon Acoustic Oscillation Survey (eBOSS). I compare the performance of different mitigation techniques and show that there is no signature of nonlinear systematics in the data. In the third part, I use the resulting improved data to constrain the initial conditions of the Universe. The methods and tools developed in this dissertation pave the path of probing the large-scale structure using data from the upcoming next generation of galaxy redshift surveys such as DESI and Euclid. This thesis presents my contribution as a member of the DESI and eBOSS collaborations.

Author : Austen M. Groener
Publisher :
Page : 254 pages
File Size : 21,88 MB
Release : 2015
Category : Cosmology
ISBN :

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We explore the intrinsic distribution of dark matter within galaxy clusters, by combining insights from the largest {\em N}-body simulations as well as the largest observational dataset of its kind. Firstly, we study the intrinsic shape and alignment of isodensities of galaxy cluster halos extracted from the MultiDark MDR1 cosmological simulation. We find that the simulated halos are extremely prolate on small scales and increasingly spherical on larger ones. Due to this trend, analytical projection along the line of sight produces an overestimate of the concentration index as a decreasing function of radius, which we quantify by using both the intrinsic distribution of 3D concentrations ($c_{200}$) and isodensity shape on weak and strong lensing scales. We find this difference to be $\sim 18\%$ ($\sim 9\%$) for low (medium) mass cluster halos with intrinsically low concentrations ($c_{200}=1-3$), while we find virtually no difference for halos with intrinsically high concentrations. Isodensities are found to be fairly well-aligned throughout the entirety of the radial scale of each halo population. However, major axes of individual halos have been found to deviate by as much as $\sim 30^{\circ}$. We also present a value-added catalog of our analysis results, which we have made publicly available to download. Following that, we then turn to observational measurements galaxy clusters. Scaling relations of clusters have made them particularly important cosmological probes of structure formation. In this work, we present a comprehensive study of the relation between two profile observables, concentration ($\mathrm{c_{vir}}$) and mass ($\mathrm{M_{vir}}$). We have collected the largest known sample of measurements from the literature which make use of one or more of the following reconstruction techniques: Weak gravitational lensing (WL), strong gravitational lensing (SL), Weak+Strong Lensing (WL+SL), the Caustic Method (CM), Line-of-sight Velocity Dispersion (LOSVD), and X-ray. We find that the concentration-mass (c-M) relation is highly variable depending upon the reconstruction technique used. We also find concentrations derived from dark matter only simulations (at approximately $\mathrm{M_{vir} \sim 10^{14} M_{\odot}}$) to be inconsistent with the WL and WL+SL relations at the $\mathrm{1\sigma}$ level, even after the projection of triaxial halos is taken into account. However, to fully determine consistency between simulations and observations, a volume-limited sample of clusters is required, as selection effects become increasingly more important in answering this. Interestingly, we also find evidence for a steeper WL+SL relation as compared to WL alone, a result which could perhaps be caused by the varying shape of cluster isodensities, though most likely reflects differences in selection effects caused by these two techniques. Lastly, we compare concentration and mass measurements of individual clusters made using more than one technique, highlighting the magnitude of the potential bias which could exist in such observational samples.Finally, we explore the large-scale environment around galaxy clusters using spectroscopically confirmed galaxies from the Sloan Digital Sky Survey (SDSS) Data Release 10. We correlate the angular structure of the distribution of galaxies (out to a distance of $\mathrm{10 h^{-1}\, Mpc}$) around 92 galaxy clusters with their corresponding mass and concentration measurements. We find that the orientation of the cluster environment on this scale has little impact on the value of cluster measurements.

Author : D. W. Sciama
Publisher : CUP Archive
Page : 264 pages
File Size : 46,36 MB
Release : 1971-08-31
Category : Science
ISBN : 9780521080699

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The exploration of the Universe, as conducted by physicists, astronomers, and cosmologists was one of the greatest intellectual adventures of the mid-twentieth century. This book, first published in 1971, tells the story of their achievements and the insight gained into the structure, history, working and scale of our Universe. Dr Sciama describes the major components of the Universe as understood at the beginning of the 1970s: the stars, galaxies, radio-galaxies and quasi-stellar objects. He discusses in detail the red shift of the lines in their optical spectra, which leads to the idea that the Universe is expanding. Theoretical discussion of the expanding Universe suggests the possibility that intergalactic space may contain a significant quantity of matter and be the seat of important physical activity. The issues involved are thoroughly debated. Also discussed is the discover and significance of the 3'K' cosmic microwave radiation, its relation to the hot big bang and the helium problem, to cosmic high energy processes and to questions of isotropy.

Author : Hao-Yi Wu
Publisher : Stanford University
Page : 234 pages
File Size : 35,99 MB
Release : 2011
Category :
ISBN :

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The acceleration of the universe, which is often attributed to "dark energy, " has posed one of the main challenges to fundamental physics. Galaxy clusters provide one of the most sensitive probes of dark energy because their abundance reflects the growth rate of large-scale structure and the expansion rate of the universe. Several large galaxy cluster surveys will soon provide tremendous statistical power to constrain the properties of dark energy; however, the constraining power of these surveys will be determined by how well systematic errors are controlled. Of these systematic errors, the dominant one comes from inferring cluster masses using observable signals of clusters, the so-called "observable--mass distribution." This thesis focuses on extracting dark energy information from forthcoming large galaxy cluster surveys, including how we maximize the cosmological information, how we control important systematics, and how precisely we need to calibrate theoretical models. We study how multi-wavelength follow-up observations can improve cluster mass calibration in optical surveys. We also investigate the impact of theoretical uncertainties in calibrating the spatial distributions of galaxy clusters on dark energy constraints. In addition, we explore how the formation history of galaxy clusters impacts the self-calibration of cluster mass. In addition, we use N-body simulations to develop a new statistical sample of cluster-size halos in order to further understand the observable--mass distribution. We study the completeness of subhalos in our cluster sample by comparing them with the satellite galaxies in the Sloan Digital Sky Survey. We also study how subhalo selections impact the inferred correlation between formation time and optical mass tracers, including cluster richness and velocity dispersion.

Author :
Publisher :
Page : pages
File Size : 30,15 MB
Release : 2016
Category :
ISBN :

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We present cosmological constraints from the Dark Energy Survey (DES) using a combined analysis of angular clustering of red galaxies and their cross-correlation with weak gravitational lensing of background galaxies. We use a 139 square degree contiguous patch of DES data from the Science Verification (SV) period of observations. Using large scale measurements, we constrain the matter density of the Universe as $\Omega_m = 0.31 \pm 0.09$ and the clustering amplitude of the matter power spectrum as $\sigma_8 = 0.74 +\pm 0.13$ after marginalizing over seven nuisance parameters and three additional cosmological parameters. This translates into $S_8$ = $\sigma_8(\Omega_m/0.3)^{0.16} = 0.74 \pm 0.12$ for our fiducial lens redshift bin at 0.35

Author : Justin Myles
Publisher :
Page : 0 pages
File Size : 50,60 MB
Release : 2023
Category :
ISBN :

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Galaxy imaging surveys represent a promising opportunity for testing cosmological models, but suffer from significant challenges associated with galaxy redshift uncertainty. I present improved techniques for the use of spectroscopic redshifts for measurements of large-scale structure with galaxy imaging surveys. I additionally present the results of the application of these techniques to data from the Sloan Digital Sky Survey (SDSS) and the Dark Energy Survey (DES). The results of my work are photometric redshift measurements of the approximately 100 million galaxies comprising the DES Year 3 Weak Lensing Source Galaxy Catalog, constraints on parameters of the Lambda-CDM cosmological model based on the gravitational lensing and clustering of the DES Year 3 source and lens galaxy catalogs, an algorithm for propagating uncertainties that have been measured in simulations to analogous measurements on data, and measurements of the incidence of projection effects in optically detected clusters of galaxies. I argue that continued development of the methods I have worked on is a promising path toward a conclusive test of Lambda-CDM with galaxy surveys.

Author : Brian J. McLean
Publisher : Springer Science & Business Media
Page : 508 pages
File Size : 29,34 MB
Release : 2012-12-06
Category : Science
ISBN : 9400914857

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Large area sky surveys are now a reality in the radio, IR, optical and X-ray passbands. In the next few years, new surveys using optical, UV and IR mosaic cameras with high throughput digital detectors will expand the dynamic range and accuracy of photometry and astrometry of objects over a significant fraction of the entire sky. Parallel X-ray and radio surveys over the same areas will produce astronomical image and spectroscopic databases of unprecedented size and quality. The combined data sets will provide significant new constraints on star formation, stellar dynamics, Galactic structure, the evolution of galaxies and large scale structure, as well as new opportunities to identify rare objects in the solar system and the Galaxy. Large area surveys have formidable data acquisition, processing, archiving, and data distribution demands and this meeting provided a forum for sharing experiences amongst workers specializing in different wavebands as well as discussing how multiband observations can reveal fundamental relationships in our understanding of the Universe.

Author : J. A. Peacock
Publisher : Cambridge University Press
Page : 700 pages
File Size : 25,50 MB
Release : 1999
Category : Science
ISBN : 9780521422703

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A comprehensive and authoritative introduction to contemporary cosmology for advanced undergraduate and graduate students.