Found 31 talks width keyword dark matter

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Friday November 13, 2009
Prof. Hiroshi Karoji
SUBARU Telescope, National Astronomical Observatory of Japan

Abstract

In 2006, NAOJ proposed to construct the Hyper Suprime-Cam (HSC) as a second generation instrument for Subaru telescope. This is a very wide-field camera covering 1.5 degrees of sky at a time. The focal plane area to be covered will be around 530mm. A total of 110 2kx4k CCD detectors will be placed adjacent to each other in order to cover this large field of view. The HSC will be a prime focus camera, and will enlarge the current field of view (FOV) of Subaru, as provided by the first generation Suprime Cam, by a factor of 10. The HSC will be the largest CCD camera in the world, and will have a total performance, as measured by the product of the telescope aperture area and the field of view, which will exceed that of all other telescopes. Only the planned LSST will have a better performance, but that will be in a time frame of three or more years later than the HSC. The main scientific goal of the HSC will be weak lensing studies over large areas of the sky. Approximately 1000 square degrees will be surveyed every year. Weak lensing distortions of background galaxies due to the large scale structure, so called cosmic shear, will be examined. From statistical properties of cosmic shear, the properties of dark energy will be constrained. Along with the weak lensing study, a large survey project is planned to use more than 200 nights of HSC and Subaru to cover interesting science topics with the large dataset.

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Thursday July 2, 2009
Miss Javiera Guedes
University of California Santa Cruz, USA

Abstract

The coalescence of a massive black hole (MBH) binary leads to the gravitational-wave recoil of the system and its ejection from the galaxy core. We have carried out N-body simulations of the motion of a M=3.7 M⊙ MBH remnant in the “Via Lactea I” Milky Way-sized halo. The hole receives a kick velocity of Vkick = 80, 120, 200, 300, and 400 km/s at redshift 1.5, and its orbit is followed for over 1 Gyr within a “live” host halo, subject only to gravity and dynamical friction against the dark matter background. We show that, owing to asphericities in the dark matter potential, the orbit of the MBH is highly non-radial, resulting in a significantly increased decay timescale compared to a spherical halo. The simulations are used to construct a semi-analytic model of the motion of the MBH in a time-varying triaxial Navarro-Frenk-White dark matter halo plus a spherical stellar bulge, where the dynamical friction force is calculated directly from the velocity dispersion tensor. Such a model should offer a realistic picture of the dynamics of kicked MBHs in situations where gas drag, friction by disk stars, and the flattening of the central cusp by the returning hole are all negligible effects. We find that, in a Milky Way-sized galaxy, a recoiling hole carrying a gaseous disk of initial mass ~2 MBH may shine as a quasar for a substantial fraction of its “wandering” phase. The long decay timescales of recoiling MBHs predicted by this study may thus be favorable to the detection of off-nuclear quasar activity.

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Monday May 18, 2009
Dr. Francisco Prada
Instituto de Astrofísica de Andalucía, Spain

Abstract

In the next decade astronomers will attempt to constrain the nature of dark matter, dark energy and the (perhaps inflationary) processes which generated structure as well as understanding the astrophysics of galaxy evolution and the formation and evolution of our Milky Way and Local Group. Large-scale spectroscopic surveys on large telescopes will be critical to achieving reliable results in all these areas. The desideratum is a survey which obtains the spectra of a few times 105 galaxies from the visible into the near IR at each of a sufficient number of redshift slices that one can follow the evolution of all interesting populations. Large samples of different stellar populations in different Local Group environments will also be targeted. I will summarize the outline of a multi-object 0.4-1.7 μ spectrograph for GTC and discuss the status of miniSIDE. MiniSIDE has been conceived as a pathfinder for a large fiber-fed survey spectrograph but will be a scientific instrument on its own, capable of providing high quality science data and be competitive within the instrumentation suite of GTC. A Letter of Intent has been submitted recently to propose miniSIDE as a facility science instrument for GTC.


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Thursday March 12, 2009
Dr. Nick Scoville
California Institute of Technology, USA

Abstract

The COSMOS survey is the largest high redshift galaxy evolution survey ever done -- imaging 2 square degrees with all major space-based and ground based observatories. I will describe the key data in the survey and then present recent results on large-scale structures, the dark matter distributions and galaxy evolution.

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Thursday February 19, 2009
Prof. Carlos Frenk
Institute for Computational Cosmology, Physics Dept, Durham University

Abstract

The standard model of cosmology -- the ``Lambda cold dark matter'' model -- is based on the idea that the dark matter is a collisionless elementary particle, probably a supersymmetric particle. This model (which mostly dates back to an early workshop in Santa Barbara in the 1980s) has been famously verified by observations of the cosmic microwave background radiation and the large-scale distribution of galaxies. However, the model has yet to be tested conclusively on the small scales appropriate to most astronomical objects, such as galaxies and clusters. I will review our current understanding of the distribution of dark matter on small scales which derives largely from large cosmological N-body simulations and I will discuss prospects for detecting dark matter, either through its gravitational effect on galaxies and clusters or, more directly, through gamma-ray annihilation radiation.

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Thursday January 22, 2009
Dr. Anne-Marie Weijmans
Leiden Observatory, the Netherlands

Abstract

From galaxy formation theory we expect galaxies to be embedded in massive dark matter haloes. For spiral and dwarf galaxies this has indeed been observationally confirmed, by modeling the kinematics from the large cold gas discs that often surround these galaxies. These gas discs are however rare in elliptical galaxies, so that we have to resort to other tracers when we want to probe their dark matter haloes, which are not always easily accessible. As a result, dark haloes for only a handful of early-type galaxies have been mapped. In this talk I will give an overview of the methods that can be used to find dark matter in early-type galaxies. I will then focus on two projects that I worked on with the integral-field spectrograph SAURON, using two different methods to constrain the dark halo. The first is based on the combination of two-dimensional ionised gas and cold gas kinematics. The second method uses SAURON as a 'photon collector', to obtain spectra at large radii in galaxies. From these spectra we can not only obtain the velocity profile and construct mass models to constrain the dark halo, but also infer the properties of the stellar halo population. I will show the results from these two projects and discuss some future prospects.

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Saturday December 20, 2008
Prof. Julio Navarro
University of Victoria, Canada

Abstract

I will review the status of our understanding of galaxy formation in the prevailing cold dark matter paradigm. After reviewing the successes and failures of the most natural predictions of this scenario I will focus on the consequences of two of its main predictions: the presence of large numbers of low-mass dark matter halos and the prevalence of accretion events during the formation of normal galaxies. In particular, I will discuss the interpretation of the recent discovery of a population of ultra-faint galaxies in the Local Group, and its relation to the profuse cold dark matter substructure expected in the Galactic halo. I will also discuss the importance that accretion events might have had in shaping not only the stellar halo but also the disk component(s) of the Milky Way.


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Monday November 17, 2008
Dr. Lee Spitler
Swinburne University, Australia

Abstract

In the Λ-CDM galaxy formation paradigm, the star formation history of a galaxy is coupled to the total mass of its dark matter halo through processes like galaxy-galaxy merging, satellite accretion, and gas retention. Globular cluster formation is known to coincide with strong star formation events in the early Universe. To develop an accurate model of galaxy formation, the relationship between such systems and their hosting dark matter halos must be understood. Employing weak gravitational lensing galaxy mass analysis, we have discovered that the number of globular clusters in a given galaxy is directly proportional to its total dark matter halo mass. This result holds in both dwarf and giant ellipticals, spirals and in all types of galaxy environments. I will present these observations and initiate a discussion on the implications for scenarios of globular cluster system formation and evolution.


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Thursday November 13, 2008
Prof. Simon White
Max-Planck Institut für Astrophysik, Garching, Germany

Abstract

In our now-standard picture for the growth of structure, dark matter halos are the basic unit of nonlinear structure in the present Universe. I will report results from simulations of galaxy-scale dark halos with more than an order of magnitude better mass resolution than any previously published work. Tests demonstrate detailed convergence for (sub)structures well below a millionth the mass of the final system. Even with such resolution the fraction of halo mass in bound subhalos does not rise above a few percent within the half-mass radius. I will also present a new simulation technique which allows structure in the dark matter distribution to be studied on very much smaller scales. This is required for accurate forecasts of the expected signal both in earth-bound experiments designed to detect dark matter directly, and in indirect detection experiments like GLAST which attempt to image dark matter annihilation radiation at gamma-ray wavelengths.

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Wednesday October 1, 2008
Dr. José Alberto Rubiño
Instituto de Astrofísica de Canarias, Spain

Abstract

Since its discovery in 1964, the cosmic microwave background (CMB) has been one of the basic pillars of the cosmological model. However, it is only very recently that CMB observations have become one of the most powerful tools in modern cosmology, due to the increasing accuracy of the experiments measuring the CMB anisotropies. In this talk, I will present a brief historical perspective of the history of the CMB observations, since the discovery until nowadays, with special emphasis on the implications and the impact of those observations in cosmology. Experiments like COBE, Tenerife, WMAP or PLANCK will be described. The last part of my talk will be devoted to describe the future of this field, and in particular, will be focused on the possibility of the detection of primordial gravitational-waves.

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