Download or read book The Role of Halo Substructure in Gamma Ray Dark Matter Searches written by Miguel A. Sánchez-Conde and published by MDPI. This book was released on 2020-05-28 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt: An important, open research topic today is to understand the relevance that dark matter halo substructure may have for dark matter searches. In the standard cosmological model, halo substructure or subhalos are predicted to be largely abundant inside larger halos, for example, galaxies such as ours, and are thought to form first and later merge to form larger structures. Dwarf satellite galaxies—the most massive exponents of halo substructure in our own galaxy—are already known to be excellent targets for dark matter searches, and indeed, they are constantly scrutinized by current gamma-ray experiments in the search for dark matter signals. Lighter subhalos not massive enough to have a visible counterpart of stars and gas may be good targets as well, given their typical abundances and distances. In addition, the clumpy distribution of subhalos residing in larger halos may boost the dark matter signals considerably. In an era in which gamma-ray experiments possess, for the first time, the exciting potential to put to test the preferred dark matter particle theories, a profound knowledge of dark matter astrophysical targets and scenarios is mandatory should we aim for accurate predictions of dark matter-induced fluxes for investing significant telescope observing time on selected targets and for deriving robust conclusions from our dark matter search efforts. In this regard, a precise characterization of the statistical and structural properties of subhalos becomes critical. In this Special Issue, we aim to summarize where we stand today on our knowledge of the different aspects of the dark matter halo substructure; to identify what are the remaining big questions, and how we could address these; and, by doing so, to find new avenues for research.
Download or read book Halo Substructure and the Nature of Dark Matter written by Mark Richard Lovell and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Role of Halo Substructure in Gamma Ray Dark Matter Searches written by Miguel A. Sánchez-Conde and published by . This book was released on 2020 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt: An important, open research topic today is to understand the relevance that dark matter halo substructure may have for dark matter searches. In the standard cosmological model, halo substructure or subhalos are predicted to be largely abundant inside larger halos, for example, galaxies such as ours, and are thought to form first and later merge to form larger structures. Dwarf satellite galaxies--the most massive exponents of halo substructure in our own galaxy--are already known to be excellent targets for dark matter searches, and indeed, they are constantly scrutinized by current gamma-ray experiments in the search for dark matter signals. Lighter subhalos not massive enough to have a visible counterpart of stars and gas may be good targets as well, given their typical abundances and distances. In addition, the clumpy distribution of subhalos residing in larger halos may boost the dark matter signals considerably. In an era in which gamma-ray experiments possess, for the first time, the exciting potential to put to test the preferred dark matter particle theories, a profound knowledge of dark matter astrophysical targets and scenarios is mandatory should we aim for accurate predictions of dark matter-induced fluxes for investing significant telescope observing time on selected targets and for deriving robust conclusions from our dark matter search efforts. In this regard, a precise characterization of the statistical and structural properties of subhalos becomes critical. In this Special Issue, we aim to summarize where we stand today on our knowledge of the different aspects of the dark matter halo substructure; to identify what are the remaining big questions, and how we could address these; and, by doing so, to find new avenues for research.
Download or read book Connecting Quarks with the Cosmos written by National Research Council and published by National Academies Press. This book was released on 2003-03-12 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advances made by physicists in understanding matter, space, and time and by astronomers in understanding the universe as a whole have closely intertwined the question being asked about the universe at its two extremesâ€"the very large and the very small. This report identifies 11 key questions that have a good chance to be answered in the next decade. It urges that a new research strategy be created that brings to bear the techniques of both astronomy and sub-atomic physics in a cross-disciplinary way to address these questions. The report presents seven recommendations to facilitate the necessary research and development coordination. These recommendations identify key priorities for future scientific projects critical for realizing these scientific opportunities.
Download or read book High Resolution Search for Dark Matter Axions in Milky Way Halo Substructure written by Leanne Delma Duffy and published by . This book was released on 2006 with total page 79 pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: The axion is one of the leading particle candidates for the universe's dark matter component. Despite possessing very small couplings, the axion's interaction with photons can be utilized to search for it using a microwave cavity detector. The Axion Dark Matter eXperiment (ADMX) uses such a detector to search for axions in our galactic halo. ADMX has recently added a new, high resolution channel to search for axions in discrete flows. ADMX's medium resolution channel searches for axions in the thermalized component of the halo. We review the motivation for the axion and its properties which make it a good dark matter candidate. We also review the arguments for the existence of discrete flows in galactic halos. A flow of discrete axions with small velocity dispersion will appear as a very narrow peak in the output of a microwave cavity detector. A high resolution search can detect such a peak with large signal to noise. We have performed such a search. The details of the high resolution axion search and analysis procedure are presented. In this search, no axion signal was found in the mass range 1.98-2.17 micro-eV. We place upper limits on the density of axions in local discrete flows based on this result.
Download or read book The Internal Structure of Halos and the Nature of Dark Matter written by Donnino Anderhalden and published by . This book was released on 2013 with total page 118 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Structure and Substructure of Cold Dark Matter Halos written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We study the structure and substructure of Lambda-CDM halos using a suite of high-resolution cosmological N-body simulations. Our analysis of the substructure population of dark matter halos focuses on their mass and peak circular velocity functions, as well as their spatial distribution and dynamics. In our analysis, we consider the whole population of subhalos physically associated with the main halo, defined as those that have, at some time, crossed within the virial radius of the main progenitor. We find that this population extends beyond 3 times the virial radius and includes objects on unorthodox orbits, several of which travel at velocities approaching the nominal escape speed from the system. We trace the origin of these unorthodox orbits to the tidal dissociation of bound groups, which results in the ejection of some systems along tidal streams. This process primarily influences low-mass systems leading to clear mass-dependent biases in their spatial distribution and kinematics: the lower the subhalo mass at accretion time the more concentrated and kinematically hotter their descendant population. When quantified in terms of present day subhalo mass these trends disappear, presumably due to the increased effect of dynamical friction and tidal stripping on massive systems. We confirm several of these results using the ultra-high resolution Aquarius simulations, which extend the dynamic range of the subhalo mass function by nearly 3 orders of magnitude. Using these simulations we confirm that the substructure mass function follows a power-law, $dN/dM\propto M^{-1.9}$, and exhibits very little halo-to-halo scatter. This implies that the total mass in substructure within a given halo is bounded to a small fraction of the total halo mass, with the smooth component dominating the halo inner regions. Using the Aquarius simulations we study the structure of galaxy-sized Lambda-CDM halos. We find that the spherically averaged density profiles become increasingly sh.
Download or read book Orbits Orbitals and Dark Matter Halos written by Tomer Dov Yavetz and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Our method relies on a wave generalization of the classic Schwarzschild approach for constructing self-consistent halos -- such a halo consists of a suitable superposition of waves instead of particle orbits, chosen to yield a desired mean density profile. As an illustration, we apply the method to spherically symmetric halos. We derive an analytic relation between the particle distribution function and the wave superposition amplitudes, and show how it simplifies in the high energy (WKB) limit. We verify the stability of such constructed halos by numerically evolving the Schrodinger-Poisson system. The proposed algorithm provides an efficient and accurate way to simulate the time-dependent halo substructures from wave interference, and to test how they will affect dynamical tracers or other observables in a galaxy. The dissertation concludes with a brief discussion of the future prospects of these two methods, especially in the context of upcoming ground- and space-based missions like Rubin LSST and the Roman Space Telescope.
Download or read book Investigating the Nature of Dark Matter with Strong Gravitational Lensing written by Daniel Alejandro Gilman and published by . This book was released on 2020 with total page 257 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dark matter makes up most of the mass in the Universe, and yet its particle nature remains unknown. Structure formation arguments provide a promising avenue to address this confounding mystery, as the mass and formation mechanism of the dark matter manifests in the abundance and density profiles of dark matter halos. Measurements of the halo mass function and the mass-concentration relation can therefore be cast as direct constraints on the particle nature of dark matter itself. Strong gravitational lensing by galaxies offers a unique probe of dark matter structure across cosmological distance, circumventing the use of luminous matter to trace the underlying dark matter. Observables from strong lens systems, particularly the image magnifications in quadruply-imaged quasars, probe the halo mass function directly on sub-galactic scales, below $10^8$ solar masses. In this low-mass regime, where halos become devoid of stars and gas, various dark matter models make unique predictions that lensing can constrain. In this dissertation, I present the development and implementation of a forward modeling framework that constrains any model based on dark matter theory, provided the model predicts the form of the halo mass function, and the density profile of individual halos. Using the framework I developed, my thesis presents an unprecedented constraint on the free-streaming length of dark matter that corresponds to a lower limit of $5.2 \rm{keV}$ on the mass of a thermal relic dark matter particle. In addition, I present the first constraint on the mass-concentration relation of Cold Dark Matter halos on sub-galactic scales across cosmological distance. The flexibility of the framework I developed broadens the scope of strong-lensing analyses to any structure formation model based on dark matter theory, underscoring the power of strong gravitational lensing as a probe of fundamental physics.
Download or read book Modern Cosmology written by Scott Dodelson and published by Academic Press. This book was released on 2003-03-13 with total page 462 pages. Available in PDF, EPUB and Kindle. Book excerpt: An advanced text for senior undergraduates, graduate students and physical scientists in fields outside cosmology. This is a self-contained book focusing on the linear theory of the evolution of density perturbations in the universe, and the anisotropiesin the cosmic microwave background.
Download or read book Radially Symmetric Patterns of Reaction Diffusion Systems written by Arnd Scheel and published by American Mathematical Soc.. This book was released on 2003 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt: Includes a paper that studies bifurcations of stationary and time-periodic solutions to reaction-diffusion systems. This title develops a center-manifold and normal form theory for radial dynamics which allows for a complete description of radially symmetric patterns.
Download or read book GLAST And Dark Matter Substructure in the Milky Way written by and published by . This book was released on 2011 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: We discuss the possibility of GLAST detecting gamma-rays from the annihilation of neutralino dark matter in the Galactic halo. We have used 'Via Lactea', currently the highest resolution simulation of cold dark matter substructure, to quantify the contribution of subhalos to the annihilation signal. We present a simulated allsky map of the expected gamma-ray counts from dark matter annihilation, assuming standard values of particle mass and cross section. In this case GLAST should be able to detect the Galactic center and several individual subhalos. One of the most exciting discoveries that the Gamma-ray Large Area Space Telescope (GLAST) could make, is the detection of gamma-rays from the annihilation of dark matter (DM). Such a measurement would directly address one of the major physics problems of our time: the nature of the DM particle. Whether or not GLAST will actually detect a DM annihilation signal depends on both unknown particle physics and unknown astrophysics theory. Particle physics uncertainties include the type of particle (axion, neutralino, Kaluza-Klein particle, etc.), its mass, and its interaction cross section. From the astrophysical side it appears that DM is not smoothly distributed throughout the Galaxy halo, but instead exhibits abundant clumpy substructure, in the form of thousands of so-called subhalos. The observability of DM annihilation radiation originating in Galactic DM subhalos depends on their abundance, distribution, and internal properties. Numerical simulations have been used in the past to estimate the annihilation flux from DM substructure, but since the subhalo properties, especially their central density profile, which determines their annihilation luminosity, are very sensitive to numerical resolution, it makes sense to re-examine their contribution with higher resolution simulations.
Download or read book Dark Matter Halos written by Yun Li and published by . This book was released on 2010 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Characterizing the Substructure of Dark Matter Halos written by Fangzhou Jiang and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Formation and Survival of Disk Galaxies written by James E. Taylor and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The dynamical evolution of substructure within dark matter halos is of central importance in determining many aspects of galaxy formation and galaxy evolution in cold dark matter cosmologies. The overall sequence in which the different stellar components of galaxies are assembled, the survival of galactic disks, the number of dwarf satellites orbiting giant galaxies, and the nature of stellar material in galactic halos all depend on the dynamics of halo substructure. In this thesis, I develop an analytic description of the evolution of substructure within a dark matter halo, and use it to construct a semi-analytic model of the formation and evolution of disk galaxies. Substructure within an individual halo is modelled as a set of distinct subhalos, orbiting in a smooth background. These subhalos evolve through three main processes: dynamical friction, tidal mass loss, and tidal heating. By including analytic descriptions of these three processes explicitly in a simple orbital integration scheme, it is possible to reproduce the results of high-resolution numerical simulations at a fraction of the computational expense. The properties of a subhalo can be estimated with an accuracy of 20%, until it has lost most of its mass or been disrupted. Using this description of satellite dynamics, I construct a semi-analytic model for the evolution of a galaxy or cluster halo. I show that this model reproduces the basic features of numerical simulations, and use it to investigate two major problems in current galaxy formation scenarios: the prediction of excessive substructure in galaxy halos, and the survival of galactic disks in halos filled with substructure. I show that the small number of dwarf galaxies observed in the Local Group can be explained by considering the effects of reionisation on star formation in small halos. The stellar luminosities predicted in this case match the observed luminosities of local satellites. The predicted spatial distribution, sizes and characteristic velocities of dwarf galaxies are also consistent with those observed locally. Many of these satellite galaxies are disrupted by tidal stripping or encounters. I investigate the properties of their debris, and show that its total mass and spatial distribution are similar to those of the stellar halo of the Milky Way. Furthermore, the stars in this debris are mainly old, satisfying another observational constraint on models of galaxy formation. Some satellites have been disrupted fairly recently, however, suggesting that coherent tidal streams may still be visible at the present day. Finally, I investigate the effects of encounters on the central disk within the main halo. I find that the rate of disruptive encounters drops off sharply after the galaxy is assembled, such that the typical disk has remained undisturbed for the past 8-10 billion years. Less disruptive encounters are more common, and disks are often heated as they re-form after their last disruption, producing components like the thick disk of the Milky Way. These results may resolve the long-standing uncertainty about disk ages in hierarchical, cold dark matter cosmologies. It is less clear whether the bulge-to-disk mass ratios predicted by the model, for the currently favoured LCDM cosmology, are consistent with observations. The relative mass of the bulge in typical disk galaxies may place an upper limit on the age of their stellar contents.
Download or read book How Dark Matter Created Dark Energy and the Sun written by Jerome Drexler and published by Universal-Publishers. This book was released on 2004 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt: Through use of a lecture-slide format, this book presents an astrophysics detective story that chronicles Jerome Drexler's literature search for astronomical clues and evidence to unveil the nature of dark matter. There are a number of mysteries in astrophysics and cosmology that have remained unsolved for decades. What is dark matter? How exactly are stars created? In 1998, it was determined from supernova studies that the expansion of the Universe was accelerating, thereby creating the mystery of dark energy. Astrophysicists have developed mutually exclusive, single-phenomenon theories for each of these three phenomena, but not a unified theory for all three of them. The author's original goal was to identify dark matter, a decades-old mystery. In the process, he developed a new theory for dark matter and illuminated the nature of dark energy and the process of Sun formation. Since dark matter may have been instrumental in the creation of galaxies and stars, the author decided to test his new dark matter theory on the formation of the Sun. The results were very encouraging. He next sought a possible link between dark matter and the accelerating expansion of the Universe, which is attributed to the mysterious dark energy. Using his dark matter theory and the laws of physics, the author explained the accelerating expansion of the Universe in a plausible manner. This book chronicles the author's search for a unified astrophysical theory and how it finally evolved.
Download or read book Dynamical Properties of Dark Matter Halo Mergers written by Anael Berrouet and published by . This book was released on 2015 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis examines the nature of mixing and heating during the merging of single, isolated dark matter halos, as well as a short discussion of the statistical nature of repeated mergers in a cosmological setting. A small set of gravitational \N-body" simulations of halo mergers are used to study heating and mixing, by measuring the dynamical properties of individual particles, as well as the overall properties of the merging halos. The accretion of mass onto a host halo is known to change the overall structure of the halo. Many previous studies have determined the general effect of mass accretion on the structure of the halo in general, and the concentration parameter in particular. Changes in this concentration parameter over the course of the merger are measured as a function of the mass of the incoming satellite and the circularity of the satellite's orbit. The amount of self-mixing in the radii and energies are also examined in order to determine the amount of memory preserved in the host halo throughout merger, as well as the amount of phase-space mixing between the host and satellite halos. Three possibilities are considered when observing how the host and satellite are mixed: that new material is layered onto the outside of the host halo and that new material falls into the center of the host halo, and that new material is evenly distributed throughout the host. Halos are found to be unevenly heated by in-falling material. The heating overall tends to make the halo expand and experience a drop in its concentration parameter due to the increase in scale radius. Examining the cumulative mass distribution and the density pro le of each halo through time, it is clear that material from the core is transported to larger radii during the merger. The scale radius presents the most relevant parameter with which to measure heating, as it represents the extent of the core of the halo. The relative increase in this observable appears to have non-trivial dependence on the mass ratio of the merging halos. We develop a simple model which provides the ability to estimate the change in the scale radius as function of the mass ratio of the merging objects. The model does not take circularity, or the total energy of the orbit into consideration, but the orbital energy of each orbit is representative of cosmological energies expected and any dependence on the circularity is actually extremely weak. Future work will examine the particular nature of these dependencies. Mixing within the host is found to be relatively inefficient, with a maximum mixing leading to a rank correlation of approximately 0:7 in radius and 0:65 in energy. This relatively small amount of mixing is even less visible when particles are binned in to radial shells, explaining previous findings of very little mixing in the literature. We also investigated the nature of phase-space mixing, that is mixing in position-velocity space, between the host and satellite halos. We expected a certain amount of phase-space mixing among the merging structures, due to the fact that they must overlap spatially, and that exchanges of energy would bring their velocity distributions closer together. Overall, merging halos will tend towards equipartition of their energies through dynamical friction. We nd that phase-space mixing is most e cient at mass ratios close to 1:1. The distance between the phase-space distributions of each halo, as measured by a statistic outlined in this work, is found to be anti-correlated to the mass ratio. Finally a few simple applications to previous work performed by Wong & Taylor (2012) as well as Fakhouri & Ma (2008) is replicated. Using the mass accretion histories developed during this work, the heating model is applied to the mass accretion histories in order to build a theoretical concentration distribution prediction for halos at redshift z = 0.
