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arXiv:0710.1303 [ps, pdf, other] :
Title: Testing Reionization with Gamma Ray Burst Absorption Spectra
Author: S. Gallerani, R. Salvaterra, A. Ferrara, T. Roy Choudhury
Comments: 5 pages, 3 figures, submitted to MNRAS
We propose a novel method to study cosmic reionization using absorption line spectra of high-redshift Gamma Ray Burst (GRB) afterglows. We show that the time evolution and the statistics of the dark portions (gaps) in the observed spectra taken during the first days after the GRB explosion represent exquisite tools to discriminate among different reionization models. We then compute the probability to find the largest gap in a given width range for burst afterglows of observed J-band flux F_J, and redshift z_GRB. We show that different reionization scenarios populate the (F_J,z_GRB) plane in a very different way, allowing to distinguish among different reionization histories. We provide here useful plots that allow a very simple and direct comparison between observations and model results. Finally, we apply our methods to GRB050904 detected at z=6.29 whose largest gap is found to be almost equal to 65 angstrom. We show that the observation of this burst provides strong indications of a highly ionized intergalactic medium at z=6, with an estimated mean neutral hydrogen fraction x_HI=7.0 \pm 4.0 10^-4 along the line of sight towards GRB050904. |
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arXiv:0710.2371 [ps, pdf, other] :
Title: Probing Non-Gaussianity In The Cosmic Microwave Background Anisotropies: One Point Distribution Function
Authors: E. Jeong, G. F. Smoot
Comments: 4 pages, 2 figures in postscripts, some typos corrected
We analyze WMAP 3 year data using the one-point distribution functions to probe the non-Gaussianity in the Cosmic Microwave Background (CMB) Anisotropy data. Computer simulations are performed to determine the uncertainties of the results. We report the non-Gaussianity parameter f_NL is constrained to 26<82 td (CL).< level confidence 95% at data combined Q+V+W for 23<75 and W-band 7<64 V-band, 12<67 Q-band,> |
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arXiv:0710.2783 [ps, pdf, other] :
Title: Void Statistics and Void Galaxies in the 2dFGRS
Authors: Alexander M. von Benda-Beckmann, Volker Mueller
Comments: 12 pages, 13 figures, submitted to MNRAS with comments by referee included. A version with high resolution plots can be downloaded at this http URL
For the 2dFGRS we study the properties of voids and of fainter galaxies within voids that are defined by brighter galaxies. Our results are compared with simulated galaxy catalogues from the Millenium simulation coupled with a semianalytical galaxy formation recipe. We derive the void size distribution and discuss its dependence on the faint magnitude limit of the galaxies defining the voids. While voids among faint galaxies are typically smaller than those among bright galaxies, the ratio of the void sizes to the mean galaxy separation reaches larger values. This is well reproduced in the mock galaxy samples studied. We provide analytic fitting functions for the void size distribution. Furthermore, we study the galaxy population inside voids defined by objects with $B_J -5\log{h}< -20$ and diameter larger than 10 \hMpc. We find a clear bimodality of the void galaxies similar to the average comparison sample. We confirm the enhanced abundance of galaxies in the blue cloud and a depression of the number of red sequence galaxies. There is an indication of a slight blue shift of the blue cloud. Furthermore, we find that galaxies in void centers have higher specific star formation rates as measured by the $\eta$ parameter. We determine the radial distribution of the ratio of early and late type galaxies through the voids. We find and discuss some differences between observations and the Millenium catalogues. |
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arXiv:0710.2484 [ps, pdf, other] :
Title: Cosmological implications of the Higgs mass measurement
Authors: J.R. Espinosa, G. Giudice, A. Riotto
Comments: 28 LaTeX pages, 6 figures
We assume the validity of the Standard Model up to an arbitrary high-energy scale and discuss what information on the early stages of the Universe can be extracted from a measurement of the Higgs mass. For Mh < 130 GeV, the Higgs potential can develop an instability at large field values. From the absence of excessive thermal Higgs field fluctuations we derive a bound on the reheat temperature after inflation as a function of the Higgs and top masses. Then we discuss the interplay between the quantum Higgs fluctuations generated during the primordial stage of inflation and the cosmological perturbations, in the context of landscape scenarios in which the inflationary parameters scan. We show that, within the large-field models of inflation, it is highly improbable to obtain the observed cosmological perturbations in a Universe with a light Higgs. Moreover, independently of the inflationary model, the detection of primordial tensor perturbations through the B-mode of CMB polarization and the discovery of a light Higgs can simultaneously occur only with exponentially small probability, unless there is new physics beyond the Standard Model. |
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arXiv:0710.3164 [ps, pdf, other] :
Title: The Importance of Satellite Quenching for the Build-Up of the Red Sequence of Present Day Galaxies
Authors: Frank C. van den Bosch, Daniel Aquino, Xiaohu Yang, H.J. Mo, Anna Pasquali, Daniel H. McIntosh, Simone M. Weinmann, Xi Kang
Comments: 14 pages, 10 figures. Submitted for publication in MNRAS
In the current paradigm, red sequence galaxies are believed to have formed as blue disk galaxies that subsequently had their star formation quenched. Since red-sequence galaxies typically have an early-type morphology, the transition from the blue to the red sequence also involves a morphological transformation. In this paper we study the impact of transformation mechanisms that operate only on satellite galaxies, such as strangulation, ram-pressure stripping and galaxy harassment. Using a large galaxy group catalogue constructed from the SDSS, we compare the colors and concentrations of satellites galaxies to those of central galaxies of the same stellar mass, adopting the hypothesis that the latter are the progenitors of the former. On average, satellites are redder and more concentrated than central galaxies of the same stellar mass. Central-satellite pairs that are matched in both stellar mass and color, however, show no average concentration difference, indicating that the transformation mechanisms affect color more than morphology. The color and concentration differences of matched central-satellite pairs are completely independent of the halo mass of the satellite galaxy, indicating that satellite-specific transformation mechanisms are equally efficient in haloes of all masses. This strongly favors strangulation as the main quenching mechanism for satellite galaxies. Finally, we determine the relative importance of satellite quenching for the build-up of the red sequence. We find that roughly 70 percent of red sequence satellite galaxies with a stellar mass of 10^9 Msun had their star formation quenched as satellites. This drops rapidly to zero with increasing stellar mass, indicating that a significant fraction of red satellites were already quenched before they became a satellite. |
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arXiv:0710.1873 [ps, pdf, other] :
Title: The scalar perturbation spectral index n_s: WMAP sensitivity to unresolved point sources
Authors: K. M. Huffenberger, H. K. Eriksen, F. K. Hansen, A. J. Banday, K. M. Gorski
Comments: 9 pages, 10 figures, 3 tables. Submitted to ApJ
Precision measurement of the scalar perturbation spectral index, n_s, from the Wilkinson Microwave Anisotropy Probe temperature angular power spectrum requires the subtraction of unresolved point source power. Here we reconsider this issue. First, we note a peculiarity in the WMAP temperature likelihood's response to the source correction: Cosmological parameters do not respond to increased source errors. An alternative and more direct method for treating this error term acts more sensibly, and also shifts n_s by ~0.3 sigma closer to unity. Second, we re-examine the source fit used to correct the power spectrum. This fit depends strongly on the galactic cut and the weighting of the map, indicating that either the source population or masking procedure is not isotropic. Jackknife tests appear inconsistent, causing us to assign large uncertainties to account for possible systematics. Third, we note that the WMAP team's spectrum was computed with two different weighting schemes: uniform weights transition to inverse noise variance weights at l = 500. The fit depends on such weighting schemes, so different corrections apply to each multipole range. For the Kp2 mask used in cosmological analysis, we prefer source corrections A = 0.012 +/- 0.005 muK^2 for uniform weighting and A = 0.015 +/- 0.005 muK^2 for N_obs weighting. Correcting WMAP's spectrum correspondingly, we compute cosmological parameters with our alternative likelihood, finding n_s = 0.970 +/- 0.017 and sigma_8 = 0.778 +/- 0.045 . This n_s is only 1.8 sigma from unity, compared to the ~2.6 sigma WMAP 3-year result. Finally, an anomalous feature in the source spectrum at l<200 remains, most strongly associated with W-band. |
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arXiv:0710.3042 [ps, pdf, other] :
Title: Large-Angular-Scale Clustering as a Clue to the Source of UHECRs
Authors: Andreas A. Berlind, Glennys R. Farrar
Comments: ICRC07
We show that future Ultra-High Energy Cosmic Ray samples should be able to distinguish whether the sources of UHECRs are hosted by galaxy clusters or ordinary galaxies, or whether the sources are uncorrelated with the large-scale structure of the universe. Moreover, this is true independently of arrival direction uncertainty due to magnetic deflection or measurement error. The reason for this is the simple property that the strength of large-scale clustering for extragalactic sources depends on their mass, with more massive objects, such as galaxy clusters, clustering more strongly than lower mass objects, such as ordinary galaxies. |
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arXiv:0710.2433 [ps, pdf, other] :
Title: Astrophysical Condition on the attolensing as a possible probe for a modified gravity theory
Authors: Takahiro Sato, Bobby E. Gunara, Kazuhiro Yamamoto, Freddy P. Zen
Comments: Accepted for publication in IJMPA
We investigate the wave effect in the gravitational lensing by a black hole with very tiny mass less than 10^-19 solar mass, which is called attolensing, motivated by a recent report that the lensing signature might be a possible probe of a modified gravity theory in the braneworld scenario. We focus on the finite source size effect and the effect of the relative motion of the source to the lens, which are influential to the wave effect in the attolensing. Astrophysical condition that the lensed interference signature can be a probe of the modified gravity theory is demonstrated. The interference signature in the microlensing system is also discussed. |
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