Download or read book Learning and Interpreting the Galaxy halo Connection in Cosmic Simulations written by Harry George Chittenden and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Large Scale Structure of the Universe written by Kana Moriwaki and published by Springer Nature. This book was released on 2022-11-01 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt: Line intensity mapping (LIM) is an observational technique that probes the large-scale structure of the Universe by collecting light from a wide field of the sky. This book demonstrates a novel analysis method for LIM using machine learning (ML) technologies. The author develops a conditional generative adversarial network that separates designated emission signals from sources at different epochs. It thus provides, for the first time, an efficient way to extract signals from LIM data with foreground noise. The method is complementary to conventional statistical methods such as cross-correlation analysis. When applied to three-dimensional LIM data with wavelength information, high reproducibility is achieved under realistic conditions. The book further investigates how the trained machine extracts the signals, and discusses the limitation of the ML methods. Lastly an application of the LIM data to a study of cosmic reionization is presented. This book benefits students and researchers who are interested in using machine learning to multi-dimensional data not only in astronomy but also in general applications.
Download or read book Applications of Cosmological Hydrodynamic Simulations on Studying the Dark Matter Halo Galaxy Connection written by and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Understanding the Circumgalactic Medium Through Hydrodynamic Simulations and Hubble s Cosmic Origins Spectrograph written by Amanda Brady Ford and published by . This book was released on 2014 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt: My dissertation focuses on a relatively new field of study: the region immediately around galaxies known as the circumgalactic medium (CGM). The CGM holds vast quantities of mass and metals, yet its connection to galaxies is not well understood. My work uses cosmological hydrodynamic simulations and comparisons to data from Hubble's Cosmic Origins Spectrograph (COS) to understand the CGM's connection to galaxy evolution, gas accretion, outflows, star formation, and baryon cycling. This includes studies of the CGM's extent and physical conditions; the cause and nature of outflows; gas dynamics, including the first comprehensive study of tracers of inflowing and outflowing gas at low redshift (z=0.25); and direct comparison of theoretical results to observational data. Chapter 1 introduces my research and show its connection to galaxy evolution. Chapter 2 investigates hydrogen and metal line absorption around low-redshift galaxies in cosmological hydrodynamic simulations. This chapter studies different models for stellar outflows, physical conditions, and dependencies on halo mass. Chapter 3 examines the flow of gas into, out of, and around galaxies using a novel particle tracking technique. This chapter examines the baryon cycle in detail for our preferred model of stellar outflows. Chapter 4 compares our model results, including two separate prescriptions for outflows, with data from COS. We contrast these wind models, showing how they cycle baryons differently, and show degeneracies in observational diagnostics. In Chapter 5, I summarize and discuss plans for future research in this field, and how it can be more fully leveraged to understand galaxy evolution.
Download or read book Insights Into Cosmological Structure Formation with Machine Learning written by Luisa Lucie-Smith and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Our modern understanding of cosmological structure formation posits that small matter density fluctuations present in the early Universe, as traced by the cosmic microwave background, grow via gravitational instability to form extended haloes of dark matter. A theoretical understanding of the structure, evolution and formation of dark matter haloes is an essential step towards unravelling the intricate connection between halo and galaxy formation, needed to test our cosmological model against data from upcoming galaxy surveys. Physical understanding of the process of dark matter halo formation is made difficult by the highly non-linear nature of the haloes' evolution. I describe a new approach to gain physical insight into cosmological structure formation based on machine learning. This approach combines the ability of machine learning algorithms to learn non-linear relationships, with techniques that enable us to physically interpret the learnt mapping. I describe applications of the method, with the aim of investigating which aspects of the early universe density field impact the later formation of dark matter haloes. First I present a case where the process of halo formation is turned into a binary classification problem; the algorithm predicts whether or not dark matter `particles' in the initial conditions of a simulation will collapse into haloes of a given mass range. Second, I present its generalization to regression, where the algorithm infers the final mass of the halo to which each particle will later belong. I show that the initial tidal shear does not play a significant role compared to the initial density field in establishing final halo masses. Finally, I demonstrate that extending the framework to deep learning algorithms such as convolutional neural networks allows us to explore connections between the early universe and late time haloes beyond those studied by existing analytic approximations of halo collapse.
Download or read book Simulations of Galaxy Formation and Large Scale Structure written by Felix Stoehr and published by Sudwestdeutscher Verlag Fur Hochschulschriften AG. This book was released on 2009-12 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work we use the N-body resimulation technique to address aspects of structure formation. In the first chapter we study the influence of the local environment of DM haloes on their properties. In the second chapter we address the so-called "substructure problem" which is one of the major challenges of the CDM model of cosmology. We perform ultra-high resolution simulations of the assembly of a Milky Way type dark matter halo within its full cosmological context and propose a new analytical fitting formula (SWTS) which provides a better fit to the simulated Milky Way halo than the NFW or Moore profiles do. In the third chapter we use our ultra-high resolution simulations to study the possible -ray signal from dark matter annihilation. If such a signal was detected, the nature of the dark matter, the answer to one of the most important questions of modern cosmology, would be known. (urn: nbn: de: bvb:19-16446)"
Download or read book Outskirts of Galaxies written by Johan H. Knapen and published by Springer. This book was released on 2017-07-09 with total page 367 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book consists of invited reviews written by world-renowned experts on the subject of the outskirts of galaxies, an upcoming field which has been understudied so far. These regions are faint and hard to observe, yet hide a tremendous amount of information on the origin and early evolution of galaxies. They thus allow astronomers to address some of the most topical problems, such as gaseous and satellite accretion, radial migration, and merging. The book is published in conjunction with the celebration of the end of the four-year DAGAL project, an EU-funded initial training network, and with a major international conference on the topic held in March 2016 in Toledo. It thus reflects not only the views of the experts, but also the scientific discussions and progress achieved during the project and the meeting. The reviews in the book describe the most modern observations of the outer regions of our own Galaxy, and of galaxies in the local and high-redshift Universe. They tackle disks, haloes, streams, and accretion as observed through deep imaging and spectroscopy, and guide the reader through the various formation and evolution scenarios for galaxies. The reviews focus on the major open questions in the field, and explore how they can be tackled in the future. This book provides a unique entry point into the field for graduate students and non-specialists, and serves as a reference work for researchers in this exciting new field.
Download or read book Secular Evolution of Galaxies written by Jesús Falcón-Barroso and published by Cambridge University Press. This book was released on 2012 with total page 657 pages. Available in PDF, EPUB and Kindle. Book excerpt: The formation and evolution of galaxies is one of the most important topics in modern astrophysics. Secular evolution refers to the relatively slow dynamical evolution due to internal processes induced by a galaxy's spiral arms, bars, galactic winds, black holes and dark matter haloes. It plays an important role in the evolution of spiral galaxies with major consequences for galactic bulges, the transfer of angular momentum, and the distribution of a galaxy's constituent stars, gas and dust. This internal evolution is in turn the key to understanding and testing cosmological models of galaxy formation and evolution. Based on the twenty-third Winter School of the Canary Islands Institute of Astrophysics, this volume presents reviews from nine world-renowned experts on the observational and theoretical research into secular processes, and what these processes can tell us about the structure and formation of galaxies. The volume provides a firm grounding for graduate students and early career researchers working on galactic dynamics and galaxy evolution.
Download or read book Galaxy Formation and Evolution written by Houjun Mo and published by Cambridge University Press. This book was released on 2010-05-20 with total page 841 pages. Available in PDF, EPUB and Kindle. Book excerpt: A coherent introduction for researchers in astronomy, particle physics, and cosmology on the formation and evolution of galaxies.
Download or read book Understanding the Epoch of Cosmic Reionization written by Andrei Mesinger and published by Springer. This book was released on 2015-11-28 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt: The dawn of the first stars, galaxies and black holes signaled a fundamental milestone in our Universe’s evolution: the Epoch of Reionization. The light from these galactic ancestors began spreading out, ionizing virtually every atom in existence. Our Universe transitioned from darkness to light, from cold to hot, from simple and boring to the wondrous cosmic zoo we see around us today. Despite its importance, observations of reionization have been few, and their interpretation has been highly controversial. Fortunately, this is rapidly changing. We will soon enter the "Big Data” era of this mysterious epoch, driven by an upcoming wave of observations with state-of-the-art telescopes as well as new sophisticated analysis tools. The aim of this volume is to summarize the current status and future outlook of the reionization field. We bring together leading experts in many sub-disciplines, highlighting the measurements that will illuminate our understanding of reionization and the cosmic dawn: (i) 21cm interferometry; (ii) high-redshift quasar spectra; (iii) high-redshift galaxy surveys; (iv) primary and secondary anisotropies of the Cosmic Microwave Background; (v) high-resolution studies of the metal content of early galaxies. We seek a roadmap to interpreting the wealth of upcoming observations. What is the best use of limited observational resources? How do we develop theoretical tools tailored for each observation? Ultimately, what will we learn about the epoch of reionization and our galactic ancestors?
Download or read book Cosmological Physics written by J. A. Peacock and published by Cambridge University Press. This book was released on 1999 with total page 700 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive and authoritative introduction to contemporary cosmology for advanced undergraduate and graduate students.
Download or read book Galaxy Proto clusters as an Interface Between Structure Cluster and Galaxy Formation written by Yi-Kuan Chiang and published by . This book was released on 2016 with total page 358 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proto-clusters, the distant progenitor large-scale structures of present day galaxy clusters, represent a key phase of cluster growth during which most of the galaxies were still rapidly forming stars. They are potentially powerful cosmological probes, and are unique laboratories to study dark matter assembly, the cosmic baryon cycle, and the environmental impact on galaxy evolution. Albeit its pivotal role in understanding cluster formation, only a small and heterogeneous sample of proto-clusters has been observed to date. Theoretical characterizations have also remained relatively unexplored. In this dissertation, I present baseline models, detailed theory predictions, and broad observational applications of proto-clusters using state-of-the-art numerical simulations and deep-wide galaxy surveys. A dual focus of both structure formation and galaxy evolution is given throughout the thesis. To prepare for large statistical studies in upcoming surveys like the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX), the Subaru Prime Focus Spectrograph (PFS) survey, and the Wide Field Infrared Survey Telescope (WFIRST) survey, I develop key machinery to connect the main observables of proto-clusters with dark matter structure formation using simulations as a guide. In Chapter 2 and 3, I present, for the first time, a thorough analysis of the main properties of proto-clusters using ~3000 clusters in a set of cosmological N-body simulations and semi-analytic galaxy models. I characterize the growth of proto-clusters and their core halos in size and mass with cosmic time. I show that the progenitor regions of galaxy clusters can already be identified in galaxy surveys at very early times (at least up to z~5), provided that the galaxy overdensities are measured on a sufficiently large scale (5--30 Mpc comoving) and with sufficient statistics. I present the overdensities in matter, dark matter halos, and galaxies as functions of present-day cluster mass, redshift, bias, and selection window size that can be used to interpret the wide range of structures found in real surveys. A table of proto-cluster candidates selected from the literature is provided, and I discuss their properties in light of our simulation predictions. In Chapter 4 I report the discovery of a large sample of proto-cluster candidates in the 1.62 deg^2 COSMOS/UltraVISTA field traced by optical/infrared selected galaxies with photometric redshifts. By comparing properly smoothed three-dimensional galaxy density maps of the observations and a set of matched simulations incorporating the main observational effects, I found 36 candidate structures at 1.610^14} M_sun. With solely photometric redshifts, I successfully rediscover two spectroscopically confirmed structures in this field, suggesting that our algorithm is robust. This work is the first large sample of uniformly selected proto-cluster candidates, providing rich targets for spectroscopic follow-up and subsequent studies of cluster formation. Because of the need of precise galaxy redshifts for density mapping and the prevalence of star formation before quenching, nearly all the proto-clusters known to date were confirmed by spectroscopy of galaxies with strong emission lines. In Chapter 5 I develop a semi-empirical model for Lya escape and generate a set of mock Lya emitter catalogs. This formalism provides a realistic modeling of the galaxy bias, the scatter of the bias, and the stochasticity of the galaxy-dark matter halo connection, which has an enormous potential for studies of the large-scale structure at high redshift. The model suggests that there are two distinct regimes to power a Lya emitter. For massive galaxies, Lya emitters are preferentially less dusty and slightly less metal enriched, while their ages and star formation rates are indistinguishable from other star-forming galaxies of the same mass. In contrast, low mass Lya emitters M_star
Download or read book Simulating Large Cosmology Surveys with Calibrated Halo Models written by Stuart Lynn and published by . This book was released on 2011 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis I present a novel method for constructing large scale mock galaxy and halo catalogues and apply this model to a number of important topics in modern cosmology. Traditionally such mocks are created through first evolving a high resolution particle simulation from a set of initial conditions to the present epoch, identifying bound structures and their evolution, and finally applying a semi-analytic prescription for galaxy formation. In contrast to this computationally expensive procedure, I use low resolution simulations to obtain a density field that traces large scale modes. From this background I sample the population statistics of halos: the number of halos which are typically found within a region of a given overdensity, to produce a halo catalogue. From the halo catalogue I then produce galaxies by appealing to the halo model. In this model the expected number of galaxies within a halo and the distribution of their properties is dependent on halo mass alone. By sampling conditional luminosity functions for a number of populations of galaxies, I produce a galaxy catalogue with luminosity and colour properties. The aim of developing algorithm is not to probe the mechanics of galaxy formation in great detail. It is instead intended as a method of rapidly producing mock galaxy and halo catalogues rapidly on modern desktop computers. The approach we will take is to try to distill the minimal algorithm required to achieve this and still provide useful catalogues for observational cosmologists. Both the conditional mass function and conditional luminosity functions required for the algorithm are calibrated from the Millennium Simulation, one of the highest resolution cosmology simulations to date, and its associated semi-analytic catalogues. In Chapter 2 I examine these statistics and provide fits to the quantities of interest. As a test of the method, in Chapter 3 I produce a halo and galaxy catalogue from the same large scale modes as the Millennium Simulation. The clustering statistics of galaxies and halos within this re-simulation are calculated and compared with those of the original. Con dent of the accuracy of the method, in Chapter 4 I populate a number of simulations, each 8 times the volume of the Millennium Simulation, and study the evolution of the Baryon Acoustic Oscillation signal. For each population (dark matter, halos and galaxies) I fit the BAO in the power spectrum to obtain the shift in the BAO peak. In Chapter 5 I extend the algorithm to produce lightcones: simulated skies in which the evolution of the Universe along the line of sight is accounted for. I simulate the geometry and limitations of a major pending survey and calculate the expected clustering signature I expect to see in both. The redshift space distortions induced by peculiar velocities of galaxies along the line of sight are determined and their ability to distinguish between gravity models is also explored. In Chapter 6 I detail a further extension to the algorithm for simulating weak gravitational lensing surveys. I use the analytic 2D surface density pro files of NFW profiles to dress each dark matter halo on a lightcone. The sum of these pro files over the entire population can be used to construct high resolution maps of the convergence. From these maps I calculate the spectrum of the convergence and compare with theoretical predictions. Finally in Chapter 7 I discuss further possible applications and extensions of the algorithm I have developed in this thesis.
Download or read book The Discovery of Cosmic Voids written by Laird A. Thompson and published by Cambridge University Press. This book was released on 2020-12-10 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: The large-scale structure of the Universe is dominated by vast voids with galaxies clustered in knots, sheets, and filaments, forming a great 'cosmic web'. In this personal account of the major astronomical developments leading to this discovery, we learn from Laird A. Thompson, a key protagonist, how the first 3D maps of galaxies were created. Using non-mathematical language, he introduces the standard model of cosmology before explaining how and why ideas about cosmic voids evolved, referencing the original maps, reproduced here. His account tells of the competing teams of observers, racing to publish their results, the theorists trying to build or update their models to explain them, and the subsequent large-scale survey efforts that continue to the present day. This is a well-documented account of the birth of a major pillar of modern cosmology, and a useful case study of the trials surrounding how this scientific discovery became accepted.
Download or read book The First Galaxies in the Universe written by Abraham Loeb and published by Princeton University Press. This book was released on 2013-01-15 with total page 572 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a comprehensive, self-contained introduction to one of the most exciting frontiers in astrophysics today: the quest to understand how the oldest and most distant galaxies in our universe first formed. Until now, most research on this question has been theoretical, but the next few years will bring about a new generation of large telescopes that promise to supply a flood of data about the infant universe during its first billion years after the big bang. This book bridges the gap between theory and observation. It is an invaluable reference for students and researchers on early galaxies. The First Galaxies in the Universe starts from basic physical principles before moving on to more advanced material. Topics include the gravitational growth of structure, the intergalactic medium, the formation and evolution of the first stars and black holes, feedback and galaxy evolution, reionization, 21-cm cosmology, and more. Provides a comprehensive introduction to this exciting frontier in astrophysics Begins from first principles Covers advanced topics such as the first stars and 21-cm cosmology Prepares students for research using the next generation of large telescopes Discusses many open questions to be explored in the coming decade
Download or read book Dark Matter and Dark Energy written by Sabino Matarrese and published by Springer Science & Business Media. This book was released on 2011-02-10 with total page 413 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book brings together reviews from leading international authorities on the developments in the study of dark matter and dark energy, as seen from both their cosmological and particle physics side. Studying the physical and astrophysical properties of the dark components of our Universe is a crucial step towards the ultimate goal of unveiling their nature. The work developed from a doctoral school sponsored by the Italian Society of General Relativity and Gravitation. The book starts with a concise introduction to the standard cosmological model, as well as with a presentation of the theory of linear perturbations around a homogeneous and isotropic background. It covers the particle physics and cosmological aspects of dark matter and (dynamical) dark energy, including a discussion of how modified theories of gravity could provide a possible candidate for dark energy. A detailed presentation is also given of the possible ways of testing the theory in terms of cosmic microwave background, galaxy redshift surveys and weak gravitational lensing observations. Included is a chapter reviewing extensively the direct and indirect methods of detection of the hypothetical dark matter particles. Also included is a self-contained introduction to the techniques and most important results of numerical (e.g. N-body) simulations in cosmology. " This volume will be useful to researchers, PhD and graduate students in Astrophysics, Cosmology Physics and Mathematics, who are interested in cosmology, dark matter and dark energy.
Download or read book Introduction to Galaxy Formation and Evolution written by Andrea Cimatti and published by Cambridge University Press. This book was released on 2019-10-17 with total page 587 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive examination of nearly fourteen billion years of galaxy formation and evolution, from primordial gas to present-day galaxies.
