Author: John David CapriottiPublisher:
ISBN:
Category :
Languages : en
Pages : 130
Book Description
Dark Matter Halos and Tidal Effects in Parabolic Galaxy Encounters
Author: John David CapriottiPublisher:
ISBN:
Category :
Languages : en
Pages : 130
Book Description
Understanding Dark Matter Halos with Tidal Caustics
Author: Robyn Ellyn SandersonPublisher:
ISBN:
Category :
Languages : en
Pages : 188
Book Description
The products of interactions between galaxies with a high mass ratio and low orbital angular momentum are studied. The interactions scatter the material from the smaller galaxy into structures with distinctive dynamics and morphology, including high local densities and a simple density profile related to properties of the participating galaxies. The role of the larger galaxy's tides in creating these structures and their relation to a well-studied class of mathematical objects motivates us to name them "tidal caustics". We study the densities achievable in tidal caustics for a typical merger of this type using an example from the Andromeda galaxy to determine whether they are sufficient to produce a detectable gamma-ray signal from self-interactions in the dark matter component, for likely particle models of dark matter. We find that the expected signal is an order of magnitude too low to be detected with current instruments. We also study the constraints that can be placed on the properties of the participating galaxies by observing the surface brightness profiles of the tidal caustics. We find that the local gravity and gravity gradient of the larger galaxy, and the energy spread and initial phase space density of the smaller galaxy, can be jointly constrained by fitting this profile. The constraints are degenerate but model-independent. We find that measurements of multiple caustics and the velocity of the material in each caustic along the line of sight give information about the orbital angular momentum and the deviations from spherical symmetry in the larger galaxy, though this information is somewhat model-dependent. We discuss the main technical difficulty in fitting the surface brightness profile: determining the inclination angle of the caustic. We demonstrate that a simple model can successfully recover the necessary parameters for some cases, and that a simple modification to this model will improve its success rate.
The Role of Halo Substructure in Gamma-Ray Dark Matter Searches
Author: Miguel A. Sánchez-CondePublisher: MDPI
ISBN: 3039360442
Category : Mathematics
Languages : en
Pages : 220
Book Description
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.
An Environmental Impact Study
Author: Philip L. ArrasDissertation Abstracts International
Author: Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 726
Book Description
The First Dark Microhalos
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 4
Book Description
Earth-mass dark matter halos are likely to have been the first bound structures to form in the Universe. Whether such objects have survived to the present day in galaxies depends on, among other factors, the rate of encounters with normal stars. In this letter, we estimate the amount of tidal heating and mass loss in microhalos as a result of stellar encounters. We find that while microhalos are only mildly heated in dwarf galaxies of low stellar density, and they should have been completely destroyed in bulge or M32-like regions of high stellar density. In disk galaxies, such as the Milky Way, the disruption rate depends strongly on the orbital parameters of the microhalo; while stochastic radial orbits in triaxial Galactic potential are destroyed first, systems on non-planar retrograde orbits with large pericenters survive the longest. Since many microhalos lose a significant fraction of their material to unbound tidal streams, the final dark matter distribution in the solar neighborhood is better described as a superposition of microstreams rather than as a set of discrete spherical clumps in an otherwise homogeneous medium. Different morphologies of microhalos have implications for direct and indirect dark matter detection experiments.
Dark and Visible Matter in Galaxies
Author: Massimo PersicPublisher:
ISBN:
Category : Science
Languages : en
Pages : 632
Book Description
At the Heart of Darkness
Author: Matthew William CraigPublisher:
ISBN:
Category :
Languages : en
Pages : 314
Book Description
Encyclopedia of Astronomy & Astrophysics
Author: P MurdinPublisher: CRC Press
ISBN: 1000523039
Category : Science
Languages : en
Pages : 5610
Book Description
In a unique collaboration, Nature Publishing Group and Institute of Physics Publishing have published the most extensive and comprehensive reference work in astronomy and astrophysics. This unique resource covers the entire field of astronomy and astrophysics and this online version includes the full text of over 2,750 articles, plus sophisticated search and retrieval functionality and links to the primary literature. The Encyclopaedia's authority is assured by editorial and advisory boards drawn from the world's foremost astronomers and astrophysicists. This first class resource is an essential source of information for undergraduates, graduate students, researchers and seasoned professionals, as well as for committed amateurs, librarians and lay people wishing to consult the definitive astronomy and astrophysics reference work.
Author: M. Wilkinson