Found 35 talks width keyword large-scale structure
Monday October 4, 2010
Prof. João MagueijoImperial College London, UK
AbstractContrary to popular belief, on very large distance scales visible matter stubbornly refuses to "fall" according to the laws of gravity of both Newton and Einstein. The paradox has led to the introduction of dark matter, purporting to explain the observed surplus of gravitational pull. The logical possibility remains that there is no dark matter, what you see is all there is, and that the paradox simply signals the break down of the Einstein-Newton theory of gravity. I will review alternative theories of gravity that do away with the need for dark matter. Surprisingly Solar system gravitational experiments, such as those associated with the LISA Pathfinder mission, might settle the score between the two approaches.
Monday March 22, 2010
Prof. Richard McMahonInstitute of Astronomy, University of Cambridge, UK
AbstractSurvey operations with the VISTA telescope with it wide field near IR camera started in Feb 2010, following a science verification phase that started in Oct, 2009. I will describe this new 4.2m wide field telescope and the ESO VISTA Public survey program. I will give details of all ESO six public surveys which will be used for a range of galactic and extragalactic science. I am the PI of the largest, by area, VISTA survey, I will focus my talk on the VISTA Hemisphere Survey and I will show how this survey will be used to find quasars in the Epoch of Reionization at redshift greater than 7. The VISTA Hemisphere Survey (VHS) has been been awarded 300 clear nights on the 4.2m ESO VISTA telescopes. VHS observations started i February, 2010 and the survey will take 5 years to complete. The VHS will cover the whole southern celestial hemisphere (dec<0) to a depth 4 magnitudes fainter than 2MASS/DENIS in at least two wavebands J and K. In the South Galactic Cap, 5000 square degrees will be imaged deeper, including H band, and will have supplemental deep multi-band grizY imaging data provided by the Dark Energy Survey (DES). The remainder of the high galactic latitude sky will be imaged in YJHK and combined with ugriz wavebands from the VST ATLAS, SDSS BOSS and Skymapper optical surveys. The medium term scientific goals include: a huge expansion in our knowledge of the lowest-mass and nearest stars; deciphering the merger history and genesis of our own Galaxy; measurement of large-scale structure out to z=1 and measuring the properties of Dark Energy; discovery of the first quasars with z > 7. In my talk, I will describe the scientific motivation and methodology of the search for quasars with z > 7.
Thursday March 12, 2009
Dr. Nick ScovilleCalifornia Institute of Technology, USA
AbstractThe 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.
Wednesday January 28, 2009
Dr. Francesco Sylos LabiniInstitute for Complex Systems, CNR, Italy
AbstractThe Sloan Digital Sky Survey is currently the largest spectroscopic survey of extragalactic objects and one of the most ambitious observational programs ever undertaken in astronomy, measuring about 1 million redshifts and thus providing a three dimensional mapping of the local universe up to a depth of several hundreds of Mpc. The main characteristic of galaxy distribution in this survey, and in the Two degree Field Galaxy redshift Survey completed few years ago, is that large scale structures have been found to extend to scales of the order of hundreds of mega parsecs. However the standard determination of a characteristic length scale, statistically describing galaxy correlations, is of only few mega parsecs: the standard explanation of this apparent mismatch is that large scale structures have small amplitude relative to the average density. We show that, in the newest galaxy samples, large scale structures are quite typical and correspond to large fluctuation in the galaxy density field, making the standard interpretation untenable. We show that the standard statistical analysis is affected by systematics which are due to inconsistent assumptions. We point out that standard theoretical models of structure formation are unable to explain the existence of the large fluctuations in the galaxy density field detected in these samples. This conclusion is reached in two ways: by considering the scale, determined by a linear perturbation analysis of a self-gravitating fluid, below which large fluctuations are expected in standard models and through the determination of statistical properties of mock galaxy catalogs generated from cosmological N-body simulations. Finally we discuss the implications of this results in relation to recent attempts to describe inhomogeneous models in general relativity and to the recent discoveries of large scale coherent bulk flows.
Tuesday November 18, 2008
Dr. Carlos Hernández-MonteagudoMax Planck Institute for Astrophysics, Germany
AbstractThe amount of baryons seen in the local Universe falls short by a factor2-5 if compared to the amount of detected baryons at intermediate (z~2)or high (z~1,100) redshift. This is the so called "missing baryon" problem in Cosmology. Hydrodynamical simulations of the large scale structure predict that most of those missing baryons should be in the form of ionized gas present in slightly overdense regions, at a temperature ranging from 10^5 to 10^7 K, conforming the "Warm Hot Intergalactic Medium" (WHIM). This WHIM would not form stars, and would not emit or absorb either in the IR, optical or UV. However, it should interact with the photons of the Cosmic Microwave Background (CMB) through two different channels: (i) Thompson scattering (where there is no energy exchange) and (ii) Compton scattering (where hot electrons transfer energy to the CMB photons, distorting their black body spectrum). I shall review the status of the search for missing baryons in the context of CMB observations and the currently most favored cosmological model. I shall also outline new methods and prospects for detecting this missing gas with upcoming CMB experiments and address the link between the cosmic baryon problem and the search for (so far undetected) bulk flows at scales of ~10 Mpc/h.
<< First « Newer 1 | 2 | 3 | 4 Older »
- Charla SMACKThursday July 1, 2021 - 10:30 GMT+1 (Aula)
- Análisis de stray light en instrumentación astrofísicaMiguel Ángel Cagigas GarcíaFriday July 2, 2021 - 12:00 GMT+1 (Aula)