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06.03.2010 07:38 - ПРАВИТЕЛСТВЕН LINK НА САЩ С ИНФОРМАЦИЯ ЗА НАУЧНИ ОТКРИТИЯ
Автор: misbis Категория: Лични дневници   
Прочетен: 3996 Коментари: 3 Гласове:
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ПРАВИТЕЛСТВЕН LINK НА САЩ  С ИНФОРМАЦИЯ ЗА  НАУЧНИ ОТКРИТИЯ

ТОВА Е ОФИЦИАЛНА УЕБ СТРАНИЦА,КЪДЕТО СЕ ПУБЛИКУВАТ НАУЧНИ ИЗСЛЕДВАНИЯ
КОСМОЛОГИЯ И ИЗВЪНГАЛАКТИЧНА АСТРОФИЗИКА.

ИНФОРМАЦИЯ ДОШЛА ОТ АРТЪР НЕЪМАН, ФИЗИК,РАБОТИЛ ДЪЛГИ ГОДИНИ ВЪВ ВОЕННИ ОБЕКТИ
И ПОНАСТОЯЩЕМ ИНФОРМАТОР НА PROJECT КАМЕЛОТ.

В НЕГО ИНТЕРЕСУВАЩИТЕ СЕ ОТ ТЕМАТА МОГАТ САМИ ДА СЕ УВЕРЯТ ВЪРХУ КАКВО РАБОТЯТ УЧЕНИТЕ В АМЕРИКА И ЧЕ ТВЪРДЕНИЕТО НА АРТЪР,ЧЕ Е РАБОТИЛ В БАЗА НА МАРС НЕ Е БЕЗПОЧВЕНО

http://xxx.lanl.gov/list/astro-ph.CO/new
xxx.lanl.gov/list/astro-ph.CO/new

chast ot nego .interesuvashtite se mogat sami da tarsiat jelanite temi
Cosmology and Extragalactic Astrophysics New submissions Submissions received from Wed 3 Mar 10 to Thu 4 Mar 10, announced Fri, 5 Mar 10 [ total of 33 entries: 1-33 ]
[ showing up to 2000 entries per page: fewer | more ]
New submissions for Fri, 5 Mar 10 [1]  arXiv:1003.0895 [ps, pdf, other] Title: The Fermi-LAT high-latitude Survey: Source Count Distributions and the Origin of the Extragalactic Diffuse Background Authors: The Fermi-LAT Collaboration Comments: Submitted to ApJ. Contact authors: M. Ajello and A. Tramacere Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE)

This is the first of a series of papers aimed at characterizing the populations detected in the high-latitude sky of the {it Fermi}-LAT survey. In this work we focus on the intrinsic spectral and flux properties of the source sample. We show that when selection effects are properly taken into account, {it Fermi} sources are on average steeper than previously found (e.g. in the bright source list) with an average photon index of 2.40$pm0.02$ over the entire 0.1--100 GeV energy band. We confirm that FSRQs have steeper spectra than BL Lac objects with an average index of 2.48$pm0.02$ versus 2.18$pm0.02$. Using several methods we build the deepest source count distribution at GeV energies deriving that the intrinsic source (i.e. blazar) surface density at F$_{100}geq10^{-9}$ ph cm$^{-2}$ s$^{-1}$ is 0.12$^{+0.03}_{-0.02}$ deg$^{-2}$. The integration of the source count distribution yields that point sources contribute 16$(pm1.8)$ % (with a systematic uncertainty of 10 %) of the GeV isotropic diffuse background. At the fluxes currently reached by LAT we can rule out the hypothesis that point-like sources (i.e. blazars) produce a larger fraction of the diffuse emission.

[2]  arXiv:1003.0896 [ps, pdf, other] Title: The effect of redshift-space distortions on projected 2-pt clustering measurements Authors: Kelly Nock, Will J. Percival, Ashley J. Ross Comments: 13 pages, 14 figures, submitted to MNRAS Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

Although redshift-space distortions only affect inferred distances and not angles, they still distort the projected angular clustering of galaxy samples selected using redshift dependent quantities. From an Eulerian view-point, this effect is caused by the apparent movement of galaxies into or out of the sample. From a Lagrangian view-point, we find that projecting the redshift-space overdensity field over a finite radial distance does not remove all the anisotropic distortions. We investigate this effect, showing that it strongly boosts the amplitude of clustering for narrow samples and can also reduce the significance of baryonic features in the correlation function. We argue that the effect can be mitigated by binning in apparent galaxy pair-centre rather than galaxy position, and applying an upper limit to the radial galaxy separation. We demonstrate this approach, contrasting against standard top-hat binning in galaxy distance, using sub-samples taken from the Hubble Volume simulations. Using a simple model for the radial distribution expected for galaxies from a survey such as the Dark Energy Survey (DES), we show that this binning scheme will simplify analyses that will measure baryonic acoustic oscillations within such galaxy samples. This technique can also be used to measure the amplitude of the redshift-space distortions. Our analysis is relevant for other photometric redshift surveys, including those made by the Panoramic Survey Telescope & Rapid Response System (Pan-Starrs) and the Large Synoptic Survey Telescope (LSST).

[3]  arXiv:1003.0898 [ps, pdf, other] Title: Dust accretion and destruction in galaxy groups and clusters Authors: Sean L. McGee, Michael L. Balogh (University of Waterloo) Comments: 10 pages, MNRAS, in press Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

We examine the dust distribution around a sample of 70,000 low redshift galaxy groups and clusters derived from the Sloan Digital Sky Survey. By correlating spectroscopically identified background quasars with the galaxy groups we obtain the relative colour excess due to dust reddening. We present a significant detection of dust out to a clustercentric distance of 30 Mpc/h in all four independent SDSS colours, consistent with the expectations of weak lensing masses of similar mass halos and excess galaxy counts. The wavelength dependence of this colour excess is consistent with the expectations of a Milky Way dust law with R_V=3.1. Further, we find that the halo mass dependence of the dust content is much smaller than would be expected by a simple scaling, implying that the dust-to-gas ratio of the most massive clusters (~10E14 Msun/h) is ~3% of the local ISM value, while in small groups (~10E12.7 Msun/h) it is ~55% of the local ISM value. We also find that the dust must have a covering fraction on the order of 10% to explain the observed color differences, which means the dust is not just confined to the most massive galaxies. Comparing the dust profile with the excess galaxy profile, we find that the implied dust-to-galaxy ratio falls significantly towards the group or cluster center. This has a significant halo mass dependence, such that the more massive groups and clusters show a stronger reduction. This suggests that either dust is destroyed by thermal sputtering of the dust grains by the hot, dense gas or the intrinsic dust production is reduced in these galaxies.

[4]  arXiv:1003.0904 [pdf, other] Title: Dark Matter Candidates from Particle Physics and Methods of Detection Authors: Jonathan L. Feng Comments: 61 pages, to appear in Annual Reviews of Astronomy and Astrophysics Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Physics - Experiment (hep-ex); High Energy Physics - Phenomenology (hep-ph)

The identity of dark matter is a question of central importance in both astrophysics and particle physics. In the past, the leading particle candidates were cold and collisionless, and typically predicted missing energy signals at particle colliders. However, recent progress has greatly expanded the list of well-motivated candidates and the possible signatures of dark matter. This review begins with a brief summary of the standard model of particle physics and its outstanding problems. We then discuss several dark matter candidates motivated by these problems, including WIMPs, superWIMPs, light gravitinos, hidden dark matter, sterile neutrinos, and axions. For each of these, we critically examine the particle physics motivations and present their expected production mechanisms, basic properties, and implications for direct and indirect detection, particle colliders, and astrophysical observations. Upcoming experiments will discover or exclude many of these candidates, and progress may open up an era of unprecedented synergy between studies of the largest and smallest observable length scales.

[5]  arXiv:1003.0905 [ps, pdf, other] Title: A Signature of Cosmic Strings Wakes in the CMB Polarization Authors: Rebecca J. Danos, Robert H. Brandenberger, Gil Holder (McGill Univ.) Comments: 8 pages, 3 figures Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

We calculate a signature of cosmic strings in the polarization of the cosmic microwave background (CMB). We find that ionization in the wakes behind moving strings gives rise to extra polarization in a set of rectangular patches in the sky whose length distribution is scale-invariant. The length of an individual patch is set by the co-moving Hubble radius at the time the string is perturbing the CMB. The polarization signal is largest for string wakes produced at the earliest post-recombination time, and for an alignment in which the photons cross the wake close to the time the wake is created. The maximal amplitude of the polarization relative to the temperature quadrupole is set by the overdensity of free electrons inside a wake which depends on the ionization fraction $f$ inside the wake. The signal can be as high as $0.06 {rm mu K}$ in degree scale polarization for a string at high redshift (near recombination) and a string tension $mu$ given by $G mu = 10^{-7}$.

[6]  arXiv:1003.0920 [ps, pdf, other] Title: The dusty heart of nearby active galaxies. I. High-spatial resolution mid-IR spectro-photometry of Seyfert galaxies Authors: S. F. Hoenig, M. Kishimoto, P. Gandhi, A. Smette, D. Asmus, W. Duschl, M. Polletta, G. Weigelt Comments: 22 pages, 13 figues, 6 tables; Accepted for publication in A&A; Note that this is the second submitted paper from the series, but we changed paper order. This one will be referred to as paper I, the previously submitted arXiv:0909.4539 will become paper II Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

We present 8-13 micron imaging and spectroscopy of 9 type 1 and 10 type 2 AGN obtained with the VLT/VISIR instrument at spatial resolution



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