tag:blogger.com,1999:blog-24011193218449582712024-03-06T12:03:22.814-08:00astro-ph.CO : Cosmology and Extragalactic AstrophysicsSite for <a href="http://communitypeerreview.blogspot.com/">Community Peer Review</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.comBlogger10800125tag:blogger.com,1999:blog-2401119321844958271.post-84775782927518809692013-08-06T00:04:00.049-07:002013-08-06T00:04:44.788-07:001011.3776 (Evgeny Akhmedov)<h2 class="title"><a href="http://arxiv.org/abs/1011.3776">Beta decay and other processes in strong electromagnetic fields</a> [<a href="http://arxiv.org/pdf/1011.3776">PDF</a>]</h2>Evgeny Akhmedov<a name='more'></a><blockquote class="abstract">We consider effects of the fields of strong electromagnetic waves on various characteristics of quantum processes. After a qualitative discussion of the effects of external fields on the energy spectra and angular distributions of the final-state particles as well as on the total probabilities of the processes (such as decay rates and total cross sections), we present a simple method of calculating the total probabilities of processes with production of non-relativistic charged particles. Using nuclear beta-decay as an example, we study the weak and strong field limits, as well as the field-induced beta-decay of nuclei stable in the absence of the external fields, both in the tunneling and multi-photon regimes. We also consider the possibility of accelerating forbidden nuclear beta-decays by lifting the forbiddeness due to the interaction of the parent or daughter nuclei with the field of a strong electromagnetic wave. It is shown that for currently attainable electromagnetic fields all effects on total beta-decay rates are unobservably small.</blockquote>View original: <a href="http://arxiv.org/abs/1011.3776">http://arxiv.org/abs/1011.3776</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-2401119321844958271.post-17814057212860933912013-08-06T00:04:00.047-07:002013-08-06T00:04:41.321-07:001308.0597 (Matthew Nichols et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0597">The Epoch of Assembly of Two Galaxy Groups: A comparative study</a> [<a href="http://arxiv.org/pdf/1308.0597">PDF</a>]</h2>Matthew Nichols, Joss Bland-Hawthorn<a name='more'></a><blockquote class="abstract">Nearby galaxy groups of comparable mass to the Local Group show global variations that reflect differences in their evolutionary history. Satellite galaxies in groups have higher levels of gas deficiency as the distance to their host decreases. The well established gas deficiency profile of the Local Group reflects an epoch of assembly starting at z<10. We investigate whether this gas deficiency profile can be used to determine the epoch of assembly for other nearby groups. We choose the M81 group as this has the most complete inventory, both in terms of membership and multi-wavelength observations. We expand our earlier evolutionary model of satellite dwarf galaxies to not only confirm this result for the Local Group but show that the more gas-rich M81 group is likely to have assembled at a later time (z<1-3).</blockquote>View original: <a href="http://arxiv.org/abs/1308.0597">http://arxiv.org/abs/1308.0597</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-2401119321844958271.post-67997599419495491382013-08-06T00:04:00.045-07:002013-08-06T00:04:40.583-07:001308.0600 (H. Fathivavsari et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0600">An investigation of the line of sight towards QSO PKS 0237-233</a> [<a href="http://arxiv.org/pdf/1308.0600">PDF</a>]</h2>H. Fathivavsari, P. Petitjean, C. Ledoux, P. Noterdaeme, R. Srianand, H. Rahmani, A. Ajabshirizadeh<a name='more'></a><blockquote class="abstract">We present a detailed analysis of absorption systems along the line of sight towards QSO PKS 0237-233 using a high resolution spectrum of signal-to-noise ratio (SNR) ~ 60-80 obtained with the Ultraviolet and Visual Echelle Spectrograph mounted on the Very Large Telescope. This line of sight is known to show a remarkable overdensity of CIV systems that has been interpreted as revealing the presence of a supercluster of galaxies. A detailed analysis of each of these absorption systems is presented. In particular, for the z_abs = 1.6359 (with two components of logN(HI) = 18.45, 19.05) and z_abs = 1.6720 (logN(H I) = 19.78) sub-Damped Ly-alpha systems (sub-DLAs), we measure accurate abundances (resp. [O/H] = -1.63(0.07) and [Zn/H] = - 0.57(0.05) relative to solar). While the depletion of refractory elements onto dust grains in both sub-DLAs is not noteworthy, photoionization models show that ionization effects are important in a part of the absorbing gas of the sub-DLA at z_abs = 1.6359 (HI is 95 percent ionized) and in part of the gas of the sub-DLA at z_abs = 1.6359. The CIV clustering properties along the line of sight is studied in order to investigate the nature of the observed overdensity. We conclude that despite the unusually high number of CIV systems detected along the line of sight, there is no compelling evidence for the presence of a single unusual overdensity and that the situation is consistent with chance coincidence.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0600">http://arxiv.org/abs/1308.0600</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-2401119321844958271.post-72479187111992422822013-08-06T00:04:00.043-07:002013-08-06T00:04:39.715-07:001308.0602 (Stephen M. Feeney et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0602">Sparse Inpainting and Isotropy</a> [<a href="http://arxiv.org/pdf/1308.0602">PDF</a>]</h2>Stephen M. Feeney, Domenico Marinucci, Jason D. McEwen, Hiranya V. Peiris, Benjamin D. Wandelt, Valentina Cammarota<a name='more'></a><blockquote class="abstract">Sparse inpainting techniques are gaining in popularity as a tool for cosmological data analysis, in particular for handling data which present masked regions and missing observations. We investigate here the relationship between inpainting techniques and the isotropy properties of cosmological maps, as for instance those arising from cosmic microwave background (CMB) experiments. In particular, we investigate the possibility that inpainted maps may exhibit anisotropies in the behaviour of higher-order angular polyspectra. We provide analytic computations and simulations of inpainted maps for a Gaussian isotropic model of CMB data, suggesting that the resulting angular trispectrum may exhibit small but non-negligible deviations from isotropy.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0602">http://arxiv.org/abs/1308.0602</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-2401119321844958271.post-41492026781060947602013-08-06T00:04:00.041-07:002013-08-06T00:04:38.825-07:001308.0604 (Janine Pforr et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0604">Recovering galaxy stellar population properties from broad-band spectral
energy distribution fitting II. The case with unknown redshift</a> [<a href="http://arxiv.org/pdf/1308.0604">PDF</a>]</h2>Janine Pforr, Claudia Maraston, Chiara Tonini<a name='more'></a><blockquote class="abstract">(Abridged) In a recent work we explored the dependence of galaxy stellar population properties derived from broad-band spectral energy distribution fitting on the fitting parameters, e.g. SFHs, age grid, metallicity, IMF, dust reddening, reddening law, filter setup and wavelength coverage. In this paper we consider also redshift as a free parameter in the fit and study whether one can obtain reasonable estimates of photometric redshifts and stellar population properties at once. We use mock star-forming as well as passive galaxies placed at various redshifts (0.5 to 3) as test particles. Mock star-forming galaxies are extracted from a semi-analytical galaxy formation model. We show that for high-z star-forming galaxies photometric redshifts, stellar masses and reddening can be determined simultaneously when using a broad wavelength coverage and a wide template setup in the fit. Masses are similarly well recovered (median ~ 0.2 dex) as at fixed redshift. For old galaxies with little recent star formation masses are better recovered than in the fixed redshift case, such that the median recovered stellar mass improves by up to 0.3 dex whereas the uncertainty in the redshift accuracy increases by only ~ 0.05. However, a failure in redshift recovery also means a failure in mass recovery. As at fixed redshift mismatches in SFH and degeneracies between age, dust and now also redshift cause underestimated ages, overestimated reddening and underestimated masses. Stellar masses are best determined at low redshift without reddening in the fit (median underestimation ~ 0.1 dex for similarly well recovered redshifts). Not surprisingly, the recovery of properties is substantially better for passive galaxies. In all cases, the recovery of physical parameters is crucially dependent on the wavelength coverage adopted in the fitting. Scaling relations for the transformation of stellar masses are provided.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0604">http://arxiv.org/abs/1308.0604</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-2401119321844958271.post-28699944602135427052013-08-06T00:04:00.039-07:002013-08-06T00:04:38.079-07:001308.0605 (Mustafa A. Amin et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0605">A Clash of Kinks: Phase shifts in colliding non-integrable solitons</a> [<a href="http://arxiv.org/pdf/1308.0605">PDF</a>]</h2>Mustafa A. Amin, Eugene A. Lim, I-Sheng Yang<a name='more'></a><blockquote class="abstract">We derive a closed-form expression for the phase shift experienced by 1+1 dimensional kinks colliding at ultra-relativistic velocities (gamma v >> 1), valid for arbitrary periodic potentials. Our closed-form expression is the leading order result of a more general scattering theory of solitary waves described in a companion paper [Amin, Lim and Yang (2013)]. This theory relies on a small kinematic parameter 1/(gamma v) << 1 rather than a small parameter in the Lagrangian. Our analytic results can be directly extracted from the Lagrangian without solving the equation of motion. Based on our closed-form expression, we prove that kink-kink and kink-antikink collisions have identical phase shifts at leading order.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0605">http://arxiv.org/abs/1308.0605</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-2401119321844958271.post-62021722135224445862013-08-06T00:04:00.037-07:002013-08-06T00:04:37.213-07:001308.0606 (Mustafa A. Amin et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0606">A scattering theory of ultra-relativistic solitons</a> [<a href="http://arxiv.org/pdf/1308.0606">PDF</a>]</h2>Mustafa A. Amin, Eugene A. Lim, I-Sheng Yang<a name='more'></a><blockquote class="abstract">We construct a perturbative framework for understanding the collision of solitons (more precisely, solitary waves) in relativistic scalar field theories. Our perturbative framework is based on the suppression of the space-time interaction area proportional to 1/(gamma v), where v is the relative velocity of an incoming solitary wave and gamma = 1/sqrt(1-v^2) >> 1. We calculate the leading order results for collisions of (1+1) dimensional kinks in periodic potentials, and provide explicit, closed form expressions for the phase shift and the velocity change after the collisions. We find excellent agreement between our results and detailed numerical simulations. Crucially, our perturbation series is controlled by a kinematic parameter, and hence not restricted to small deviations around integrable cases such as the Sine-Gordon model.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0606">http://arxiv.org/abs/1308.0606</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-2401119321844958271.post-45702046187615128262013-08-06T00:04:00.035-07:002013-08-06T00:04:36.568-07:001308.0609 (Angela Sandrinelli et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0609">Long and short term variability of seven blazars in six
near-infrared/optical bands</a> [<a href="http://arxiv.org/pdf/1308.0609">PDF</a>]</h2>Angela Sandrinelli, Stefano Covino, Aldo Treves<a name='more'></a><blockquote class="abstract">Context. We present the light curves of six BL Lac objects, PKS 0537-441, PKS 0735+17, OJ 287, PKS 2005-489, PKS 2155-304, W Comae, and of the flat spectrum radio quasar PKS 1510-089, as a part of a photometric monitoring program in the near-infrared/optical bands started in 2004. All sources are Fermi blazars. Aims. Our purpose is to investigate flux and spectral variability on short and long time scales. Systematic monitoring, independent of the activity of the source, guarantees large sample size statistics, and allows an unbiased view of different activity states on weekly or daily time scales for the whole timeframe and on nightly timescales for some epochs. Methods. Data were obtained with the REM telescope located at the ESO premises of La Silla (Chile). Light curves were gathered in the optical/near-infrared VRIJHK bands from April 2005 to June 2012. Results. Variability >= 3 mag is observed in PKS 0537-441, PKS 1510-089 and PKS 2155-304, the largest ranges spanned in the near-infrared. The color intensity plots show rather different morphologies. The spectral energy distributions in general are well fitted by a power law, with some deviations that are more apparent in low states. Some variability episodes during a night interval are well documented for PKS 0537-441 and PKS 2155-304. For the latter source the variability time scale implies a large relativistic beaming factor.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0609">http://arxiv.org/abs/1308.0609</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-2401119321844958271.post-91123816540434468842013-08-06T00:04:00.033-07:002013-08-06T00:04:35.601-07:001308.0618 (Manoj Kaplinghat et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0618">Self-interacting Dark Matter Benchmarks</a> [<a href="http://arxiv.org/pdf/1308.0618">PDF</a>]</h2>Manoj Kaplinghat, Sean Tulin, Hai-Bo Yu<a name='more'></a><blockquote class="abstract">Dark matter self-interactions have important implications for the distributions of dark matter in the Universe, from dwarf galaxies to galaxy clusters. We present benchmark models that illustrate characteristic features of dark matter that is self-interacting through a new light mediator. These models have self-interactions large enough to change dark matter densities in the centers of galaxies in accord with observations, while remaining compatible with large-scale structure data and all astrophysical observations such as halo shapes and the Bullet Cluster. These observations favor a mediator mass in the 10 - 100 MeV range and large regions of this parameter space are accessible to direct detection experiments like LUX, SuperCDMS, and XENON1T.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0618">http://arxiv.org/abs/1308.0618</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-2401119321844958271.post-64576883979087044502013-08-06T00:04:00.031-07:002013-08-06T00:04:34.928-07:001308.0630 (Fernando de Simoni et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0630">Large-scale analysis of the SDSS-III DR8 photometric luminous galaxies
angular correlation function</a> [<a href="http://arxiv.org/pdf/1308.0630">PDF</a>]</h2>Fernando de Simoni, Flavia Sobreira, Aurelio Carnero, Ashley J. Ross, Hugo O. Camacho, Rogerio Rosenfeld, Marcos Lima, Luiz A. N. da Costa, Marcio A. G. Maia<a name='more'></a><blockquote class="abstract">We analyze the large-scale angular correlation function (ACF) of the CMASS Luminous Galaxies (LGs), a photometric-redshift catalog based on the 8th data release (DR8) of the SDSS-III. This catalog contains over 600,000 LGs in the range $0.45 \leq z \leq 0.65$, which was split into four redshift shells of constant width. First, we estimate the constraints on the redshift space distortion (RSD) parameters $b\sigma_8$ and $f\sigma_8$, where $b$ is the galaxy bias, $f$ the growth rate and $\sigma_8$ is the normalization of the perturbations, finding that they vary appreciably among different redshift shells, in agreement with previous results using DR7 data. When assuming constant RSD parameters over the survey redshift range, we obtain $f\sigma_8 = 0.69 \pm 0.21$, which agrees at the $1.5\sigma$ level with BOSS DR9 spectroscopic results. Next, we performed two cosmological analyses, where relevant parameters not fitted were kept fixed at their fiducial values. In the first analysis, we extracted the BAO peak position for the four redshift shells, and combined with the sound horizon scale from WMAP7 to produce the constraints $\Omega_{m}=0.249 \pm 0.031$ and $w=-0.885 \pm 0.145$. In the second analysis, we used the ACF full shape information to constrain cosmology using real data for the first time, finding $\Omega_{m} = 0.280 \pm 0.022$ and $f_b = \Omega_b/\Omega_m = 0.211 \pm 0.026$. These results are in good agreement with WMAP7 findings, showing that the ACF can be efficiently applied to constrain cosmology in future photometric galaxy surveys.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0630">http://arxiv.org/abs/1308.0630</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-2401119321844958271.post-32542403112001093692013-08-06T00:04:00.029-07:002013-08-06T00:04:33.892-07:001308.0728 (Gordon P. Garmire)<h2 class="title"><a href="http://arxiv.org/abs/1308.0728">X-ray discovery of a dwarf-galaxy galaxy collision</a> [<a href="http://arxiv.org/pdf/1308.0728">PDF</a>]</h2>Gordon P. Garmire<a name='more'></a><blockquote class="abstract">We report the discovery of a probable dwarf galaxy colliding with NGC 1232. This collision is visible only in the X-ray spectral band, and it is creating a region of shocked gas with a temperature of 5.8 MK covering an impact area 7.25 kpc in diameter. The X-ray luminosity is 3.7 x1038ergs s-1. The long lifetime of this gas against radiative and adiabatic cooling should permit the use of the luminous afterglow from such collisions to be used as a way of estimating their importance in galaxy evolution.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0728">http://arxiv.org/abs/1308.0728</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-2401119321844958271.post-8005542611165601972013-08-06T00:04:00.027-07:002013-08-06T00:04:30.890-07:001308.0808 (I. Marti-Vidal et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0808">Limit to the radio emission from a putative central compact source in
SN1993J</a> [<a href="http://arxiv.org/pdf/1308.0808">PDF</a>]</h2>I. Marti-Vidal, J. M. Marcaide<a name='more'></a><blockquote class="abstract">SN1993J in M81 is the best studied young radio-luminous supernova in the Northern Hemisphere. We recently reported results from the analysis of a complete set of VLBI observations of this supernova at 1.7, 2.3, 5.0, and 8.4 GHz, covering a time baseline of more than one decade. Those reported results were focused on the kinematics of the expanding shock, the particulars of its evolving non-thermal emission, the density profile of the circumstellar medium, and the evolving free-free opacity by the supernova ejecta. In the present paper, we complete our analysis by performing a search for any possible signal from a compact source (i.e., a stellar-mass black hole or a young pulsar nebula) at the center of the expanding shell. We have performed a stacking of all our VLBI images at each frequency, after subtraction of our best-fit shell model at each epoch, and measured the peak intensity in the stacked residual image. Given the large amount of available global VLBI observations, the stacking of all the residual images allows us to put upper limits to the eventual emission of a putative compact central source at the level of $\sim102$ $\mu$Jy at 5 GHz (or, more conservatively, $\sim192$ $\mu$Jy, if we make a further correction for the ejecta opacity) and somewhat larger at other wavelengths.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0808">http://arxiv.org/abs/1308.0808</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-2401119321844958271.post-33488920836178654122013-08-06T00:04:00.025-07:002013-08-06T00:04:30.038-07:001308.0834 (Omer Farooq et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0834">Observational constraints on non-flat dynamical dark energy cosmological
models</a> [<a href="http://arxiv.org/pdf/1308.0834">PDF</a>]</h2>Omer Farooq, Data Mania, Bharat Ratra<a name='more'></a><blockquote class="abstract">We constrain two non-flat time-evolving dark energy cosmological models by using Hubble parameter data, Type Ia supernova apparent magnitude measurements, and baryonic acoustic oscillation peak length scale observations. The inclusion of space curvature as a free parameter in the analysis results in a significant broadening of the allowed range of values of the parameter that governs the time evolution of the dark energy density in these models. While consistent with the "standard" spatially-flat $\Lambda$CDM cosmological model, these data are also consistent with a range of mildly non-flat, slowly time-varying dark energy models. After marginalizing over all other parameters, these data require the averaged magnitude of the curvature density parameter $|\Omega_{k0}| \lesssim 0.15$ at 1$\sigma$ confidence.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0834">http://arxiv.org/abs/1308.0834</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-2401119321844958271.post-33094612686550593682013-08-06T00:04:00.023-07:002013-08-06T00:04:28.988-07:001308.0837 (András Kovács et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0837">Phase statistics of the WMAP 7 year data</a> [<a href="http://arxiv.org/pdf/1308.0837">PDF</a>]</h2>András Kovács, István Szapudi, Zsolt Frei<a name='more'></a><blockquote class="abstract">We performed a comprehensive statistical analysis using complex phases of the a_lm coefficients computed from the most recent data of the Wilkinson Microwave Anisotropy Probe (WMAP). Our aim was to confirm or constrain the presence of non-Gaussianities in the data. We found phase correlations - that suggest non-Gaussianity - at high-l in a_lm coefficients by applying various statistical tests. Most of all, we detected a non-Gaussian signal reaching a significance of 4.7 sigma using random walk statistics and simulations. However, our conclusion is that the non-Gaussian behavior is due to contamination from galactic foregrounds that show up in small scales only. When masked out the contaminated regions, we found no significant non-Gaussianity. Furthermore, we constrained the f_NL parameter using CMB simulations that mimic primordial non-Gaussianity. Our estimate is f_NL=40 +/- 200, in agreement with previous measurements and inflationary expectations.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0837">http://arxiv.org/abs/1308.0837</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-2401119321844958271.post-19782607364636534572013-08-06T00:04:00.021-07:002013-08-06T00:04:28.196-07:001308.0847 (Michael Levi et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0847">The DESI Experiment, a whitepaper for Snowmass 2013</a> [<a href="http://arxiv.org/pdf/1308.0847">PDF</a>]</h2>Michael Levi, Chris Bebek, Timothy Beers, Robert Blum, Robert Cahn, Daniel Eisenstein, Brenna Flaugher, Klaus Honscheid, Richard Kron, Ofer Lahav, Patrick McDonald, Natalie Roe, David Schlegel, representing the DESI collaboration<a name='more'></a><blockquote class="abstract">The Dark Energy Spectroscopic Instrument (DESI) is a massively multiplexed fiber-fed spectrograph that will make the next major advance in dark energy in the timeframe 2018-2022. On the Mayall telescope, DESI will obtain spectra and redshifts for at least 18 million emission-line galaxies, 4 million luminous red galaxies and 3 million quasi-stellar objects, in order to: probe the effects of dark energy on the expansion history using baryon acoustic oscillations (BAO), measure the gravitational growth history through redshift-space distortions, measure the sum of neutrino masses, and investigate the signatures of primordial inflation. The resulting 3-D galaxy maps at z<2 and Lyman-alpha forest at z>2 will make 1%-level measurements of the distance scale in 35 redshift bins, thus providing unprecedented constraints on cosmological models.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0847">http://arxiv.org/abs/1308.0847</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-2401119321844958271.post-35928185112436707992013-08-06T00:04:00.019-07:002013-08-06T00:04:27.181-07:001308.0860 (Luis P. Chimento et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0860">Nonbaryonic dark matter and scalar field coupled with a transversal
interaction plus decoupled radiation</a> [<a href="http://arxiv.org/pdf/1308.0860">PDF</a>]</h2>Luis P. Chimento, Martín G. Richarte<a name='more'></a><blockquote class="abstract">We analyze a universe filled with interacting dark matter, a scalar field accommodated as dark radiation along with dark energy plus a decoupled radiation term within the framework of spatially flat Friedmann-Robertson-Walker (FRW) spacetime. We work in a three-dimensional internal space spanned by the interaction vector and use a transversal interaction $\mathbf{Q_t}$ for solving the source equation in order to find all the interacting component energy densities. We asymptotically reconstruct the scalar field and potential from an early radiation era to the late dominate dark energy one, passing through an intermediate epoch dominated by dark matter. We apply the $\chi^{2}$ method to the updated observational Hubble data for constraining the cosmic parameters, contrast with the Union 2 sample of supernovae, and analyze the amount of dark energy in the radiation era. It turns out that our model fulfills the severe bound of $\Omega_{\rm \phi}(z\simeq 1100)<0.018$ at $2\sigma$ level, is consistent with the recent analysis that includes cosmic microwave background anisotropy measurements from the Atacama Cosmology Telescope and the South Pole Telescope along with the future constraints achievable by Planck and CMBPol experiments, and satisfies the stringent bound $\Omega_{\rm \phi}(z\simeq 10^{10})<0.04$ at $2\sigma$ level in the big-bang nucleosynthesis epoch.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0860">http://arxiv.org/abs/1308.0860</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-2401119321844958271.post-74216264883667561432013-08-06T00:04:00.017-07:002013-08-06T00:04:26.117-07:001308.0878 (Daniel M. Kaplan et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0878">Measuring Antimatter Gravity with Muonium</a> [<a href="http://arxiv.org/pdf/1308.0878">PDF</a>]</h2>Daniel M. Kaplan, Derrick Mancini, Thomas J. Phillips, Thomas J. Roberts, Richard Gustafson<a name='more'></a><blockquote class="abstract">We consider a measurement of the gravitational acceleration of antimatter, gbar, using muonium. A monoenergetic, low-velocity, horizontal muonium beam will be formed from a surface-muon beam using a novel technique and directed at an atom interferometer. The measurement requires a precision three-grating interferometer: the first grating pair creates an interference pattern which is analyzed by scanning the third grating vertically using piezo actuators. State-of-the-art nanofabrication can produce the needed membrane grating structure in silicon nitride or ultrananoscrystalline diamond. With 100 nm grating pitch, a 10% measurement of gbar can be made using some months of surface-muon beam time. This will be the first gravitational measurement of leptonic matter, of 2nd-generation matter and, possibly, the first measurement of the gravitational acceleration of antimatter.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0878">http://arxiv.org/abs/1308.0878</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-2401119321844958271.post-28694869379011898152013-08-06T00:04:00.015-07:002013-08-06T00:04:25.268-07:001308.0884 (K. Thorat et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0884">Environments of Extended Radio Sources in the ATLBS Survey</a> [<a href="http://arxiv.org/pdf/1308.0884">PDF</a>]</h2>K. Thorat, L. Saripalli, R. Subrahmanyan<a name='more'></a><blockquote class="abstract">We present a study of the environments of extended radio sources in the Australia Telescope Low Brightness Survey (ATLBS). The radio sources were selected from the Extended Source Sample (ATLBS-ESS), which is a well defined sample containing the most extended of radio sources in the ATLBS sky survey regions. The environments were analyzed using 4-m CTIO Blanco telescope observations carried out for ATLBS fields in the SDSS ${\rm r}^{\prime}$ band. We have estimated the properties of the environments using smoothed density maps derived from galaxy catalogs constructed using these optical imaging data. The angular distribution of galaxy density relative to the axes of the radio sources has been quantified by defining anisotropy parameters that are estimated using a new method presented here. Examining the anisotropy parameters for a sub-sample of extended double radio sources that includes all sources with pronounced asymmetry in lobe extents, we find good evidence for environmental anisotropy being the dominant cause for lobe asymmetry in that higher galaxy density occurs almost always on the side of the shorter lobe, and this validates the usefulness of the method proposed and adopted here. The environmental anisotropy parameters have been used to examine and compare the environments of FRI and FRII radio sources in two redshift regimes ($z<0.5$ and $z>0.5$). Wide-angle tail sources and Head-tail sources lie in the most overdense environments. The Head-tail source environments (for the HT sources in our sample) display dipolar anisotropy in that higher galaxy density appears to lie in the direction of the tails. Excluding the Head-tail and Wide-angle tail sources, subsamples of FRI and FRII sources from the ATLBS survey appear to lie in similar moderately overdense environments, with no evidence for redshift evolution in the regimes studied herein.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0884">http://arxiv.org/abs/1308.0884</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-2401119321844958271.post-1491094255095512782013-08-06T00:04:00.013-07:002013-08-06T00:04:24.270-07:001308.0886 (Yi Zheng et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0886">Peculiar Velocity Decomposition, Redshift Space Distortion and Velocity
Reconstruction in Redshift Surveys II. Dark Matter Velocity Statistics</a> [<a href="http://arxiv.org/pdf/1308.0886">PDF</a>]</h2>Yi Zheng, Pengjie Zhang, Yipeng Jing, Weipeng Lin, Jun Pan<a name='more'></a><blockquote class="abstract">Massive spectroscopic redshift surveys open a promising window to accurately measure peculiar velocity at cosmological distances through redshift space distortion (RSD). In paper I of this series of work we proposed to decompose peculiar velocity into three eigen-modes (v_\delta, v_S and v_B) in order to facilitate the RSD modeling and peculiar velocity reconstruction. In the current paper we measure the dark matter RSD related statistics of the velocity eigen-modes through a set of N-body simulations, including the velocity power spectra, correlation functions, one-point probability distribution functions, cumulants and the damping functions describing the Finger of God effect. (1) The power spectrum measurement shows that these velocity components have distinctly different spatial distribution and redshift evolution. In particular, we measure the window function \tilde{W}(k,z), which describes the impact of nonlinear evolution on the v_\delta-density relation. We confirm that it can induce a significant systematic error of O(10%) in RSD cosmology. We demonstrate that \tilde{W} can be accurately described by a simple fitting formula with one or two free parameters. (2) The correlation function measurement shows that the correlation length is O(100), O(10) and O(1) Mpc for v_\delta, v_S and v_B respectively. These correlation lengths determine where we can treat the velocity fields as spatially uncorrelated. (3) The velocity PDFs and cumulants quantify non-Gaussianities of the velocity fields. We confirm speculation in paper I that v_\delta\ is largely Gaussian, nevertheless with non-negligible non-Gaussianity, v_B is significantly non-Gaussian. We also measure the damping functions. Despite the observed non-Gaussianities, the damping functions and hence the FOG effect are all well approximated as Gaussian ones at scales of interest.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0886">http://arxiv.org/abs/1308.0886</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-2401119321844958271.post-75395766965284251192013-08-06T00:04:00.011-07:002013-08-06T00:04:23.100-07:001308.0902 (Woei Chet Lim et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0902">Spherically symmetric cosmological spacetimes with dust and radiation -
numerical implementation</a> [<a href="http://arxiv.org/pdf/1308.0902">PDF</a>]</h2>Woei Chet Lim, Marco Regis, Chris Clarkson<a name='more'></a><blockquote class="abstract">We present new numerical cosmological solutions of the Einstein Field Equations. The spacetime is spherically symmetric with a source of dust and radiation approximated as a perfect fluid. The dust and radiation are necessarily non-comoving due to the inhomogeneity of the spacetime. Such a model can be used to investigate non-linear general relativistic effects present during decoupling or big-bang nucleosynthesis, as well as for investigating void models of dark energy with isocurvature degrees of freedom. We describe the full evolution of the spacetime as well as the redshift and luminosity distance for a central observer. After demonstrating accuracy of the code, we consider a few example models, and demonstrate the sensitivity of the late time model to the degree of inhomogeneity of the initial radiation contrast.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0902">http://arxiv.org/abs/1308.0902</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-2401119321844958271.post-42439270871946305022013-08-06T00:04:00.009-07:002013-08-06T00:04:22.251-07:001308.0924 (Pranati K. Rath et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0924">Testing the Dipole Modulation Model in CMBR</a> [<a href="http://arxiv.org/pdf/1308.0924">PDF</a>]</h2>Pranati K. Rath, Pankaj Jain<a name='more'></a><blockquote class="abstract">The hemispherical power asymmetry, observed in the CMBR data, has generally been interpreted in terms of the dipole modulation model for the temperature fluctuations. Here we point out that this model leads to several predictions, which can be directly tested in the current data. We also suggest tests of the hemispherical power asymmetry in real space. We do not find a significant signal of the dipole modulation model in WMAP and PLANCK data. Hence the detected hemispherical anisotropy cannot be consistently represented in terms of the dipole modulation model. It probably represents a more complex anisotropic model.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0924">http://arxiv.org/abs/1308.0924</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-2401119321844958271.post-19403063961859912462013-08-06T00:04:00.007-07:002013-08-06T00:04:21.560-07:001308.0970 (Candace Partridge et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0970">Weighing the Local Group in the Presence of Dark Energy</a> [<a href="http://arxiv.org/pdf/1308.0970">PDF</a>]</h2>Candace Partridge, Ofer Lahav, Yehuda Hoffman<a name='more'></a><blockquote class="abstract">We revise the mass estimate of the Local Group (LG) when Dark Energy (in the form of the Cosmological Constant) is incorporated into the Timing Argument (TA) mass estimator for the Local Group (LG). Assuming the age of the Universe and the Cosmological Constant according to the recent values from the Planck CMB experiment, we find the mass of the LG to be M_TAL = (4.73 +- 1.03) x 10^{12} M_sun, which is 13% higher than the classical TA mass estimate. This partly explains the discrepancy between earlier results from LCDM simulations and the classical TA. When a similar analysis is performed on 16 LG-like galaxy pairs from the CLUES simulations, we find that the scatter in the ratio of the virial to the TA estimated mass is given by M_vir/M_TAL = 1.04 +-0.16. Applying it to the LG mass estimation we find a calibrated M_vir = (4.92 +- 1.08 (obs) +- 0.79 (sys)) x 10^{12} M_sun.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0970">http://arxiv.org/abs/1308.0970</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-2401119321844958271.post-20439064580860560882013-08-06T00:04:00.005-07:002013-08-06T00:04:20.798-07:001308.0992 (T. Venturi et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0992">Radio emission at the centre of the galaxy cluster Abell 3560: evidence
for core sloshing?</a> [<a href="http://arxiv.org/pdf/1308.0992">PDF</a>]</h2>T. Venturi, M. Rossetti, S. Bardelli, S. Giacintucci, D. Dallacasa, M. Cornacchia, N. Kantharia<a name='more'></a><blockquote class="abstract">Previous radio observations of the galaxy cluster A3560 in the Shapley Concentration showed complex radio emission associated with the brightest cluster member.To understand its origin we observed it with the GMRT, the VLA and ATCA at 240 and 610 MHz, 1.28,1.4, 2.3,4.8 and 8.4 GHz, and performed a detailed morphological and spectral study of the radio emission associated with the BCG. We also observed the cluster with XMM-Newton and Chandra to derive the properties of the ICM. The radio emission of the N-E nucleus of the dumb-bell BCG shows an active radio galaxy, plus aged diffuse emission, which is not refurbished at present. Our Chandra data show that the radio active nucleus of the BCG has extended X-ray emission, which we classify as a low-luminosity corona. A residual image of the XMM-Newton brightness shows the presence of a spiral-like feature, which we interpret as the signature of gas sloshing. The presence of a subgroup is clear in the surface brightness residual map, and in the XMM-Newton temperature analysis. The optical 2D analysis shows substructure in A3560. A galaxy clump was found at the location of the X-ray subgroup, and another group is present south of the cluster core, close to the spiral-like feature. The aged part of the radio emission closely follows the spiral pattern of the X-ray residual brightness distribution, while the two active radio lobes are bent in a completely different direction. We conclude that the complex radio emission associated with the cluster BCG is the result of a minor merger event in A3560. The aged diffuse emission is strongly affected by the sloshing motion in the ICM. On the other hand, the bent jets and lobes of the current radio AGN activity may reflect a complex gas velocity field in the innermost cluster regions and/or sloshing-induced oscillations in the motion of the cD galaxy.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0992">http://arxiv.org/abs/1308.0992</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-2401119321844958271.post-59028651110796148662013-08-06T00:04:00.003-07:002013-08-06T00:04:19.923-07:001308.1019 (C. Wetterich)<h2 class="title"><a href="http://arxiv.org/abs/1308.1019">Variable gravity Universe</a> [<a href="http://arxiv.org/pdf/1308.1019">PDF</a>]</h2>C. Wetterich<a name='more'></a><blockquote class="abstract">For variable gravity models the strength of gravity, as measured by Newton's "constant" or the Planck mass, depends on the value of a scalar field, the cosmon. Within this framework we discuss two simple models with a quadratic or constant cosmon potential. They describe a realistic cosmological sequence of inflation, radiation- and matter-domination. Dark Energy constitutes a small, almost constant fraction of the energy density during the radiation and matter dominated epochs (Early Dark Energy). In the present epoch we witness a transition to a new Dark Energy dominated epoch. In our models the inflaton and the scalar field of quintessence are the same cosmon field. It is remarkable how simple models involving only one scalar field can be compatible with all presently available cosmological observations. Our models are free of a big bang singularity. The stability of solutions generates an arrow of time.</blockquote>View original: <a href="http://arxiv.org/abs/1308.1019">http://arxiv.org/abs/1308.1019</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-2401119321844958271.post-25927325161220211262013-08-06T00:04:00.001-07:002013-08-06T00:04:18.943-07:001308.1029 (Renata Zukanovich Funchal et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.1029">The Physics of Neutrinos</a> [<a href="http://arxiv.org/pdf/1308.1029">PDF</a>]</h2>Renata Zukanovich Funchal, Benoit Schmauch, Gaëlle Giesen<a name='more'></a><blockquote class="abstract">These lecture notes are based on a course given at Institut de Physique Th\'eorique of CEA/Saclay in January/February 2013.</blockquote>View original: <a href="http://arxiv.org/abs/1308.1029">http://arxiv.org/abs/1308.1029</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0