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Correlated Fluctuations in Luminosity Distance and the Importance of Peculiar Motion in Supernova Surveys


Large scale structure introduces two different kinds of errors in the luminosity distance estimatesfrom standardizable candles such as supernovae Ia (SNe) – a Poissonian scatter for each SN and acoherent component due to correlated fluctuations between different SNe. Increasing the number ofSNe helps reduce the first type of error but not the second. The coherent component has been largelyignored in forecasts of dark energy parameter estimation from upcoming SN surveys. For instanceit is commonly thought, based on Poissonian considerations, that peculiar motion is unimportant,even for a low redshift SN survey such as the Nearby Supernova Factory (SNfactory; z

ادامه مطلب  
Galaxy Peculiar Velocities From Large-Scale Supernova Surveys as a Dark Energy Probe


Upcoming imaging surveys such as the Large Synoptic Survey Telescope will repeatedly scanlarge areas of sky and have the potential to yield million-supernova catalogs. Type Ia supernovae are excellent standard candles and will provide distance measures that suffice to detect mean pairwise velocities of their host galaxies. We show that when combining these distance measures with photometric redshifts for either the supernovae or their host galaxies, the mean pairwise velocities of the host galaxies will provide a dark energy probe which is competitive with other widely discussed methods. Adding information from this test to type Ia supernova photometric luminosity distances from the sa

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On the perturbation of the luminosity distance by peculiar motions


We consider some aspects of the perturbation to the luminosity distance d(z) thatare of relevance for SN1a cosmology and for future peculiar velocity surveys at non-negligible redshifts.1) Previous work has shown that the correction to the lowest order perturba-tion d/d = −v/cz has the peculiar characteristic that it appears to depend on theabsolute state of motion of sources, rather than on their motion relative to that ofthe observer. The resolution of this apparent violation of the equivalence principle isthat it is necessary to allow for evolution of the velocities with time, and also, whenconsidering perturbations on the scale of the observer-source separation, to includethe gravitational red

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Fluctuations of the luminosity distance


We derive an expression for the luminosity distance in a perturbed Friedmann universe. We definethe correlation function and the power spectrum of the luminosity distance fluctuations and expressthem in terms of the initial spectrum of the Bardeen potential. We present semi-analytical resultsfor the case of a pure CDM (cold dark matter) universe. We argue that the luminosity distancepower spectrum represents a new observational tool which can be used to determine cosmologicalparameters. In addition, our results shed some light into the debate whether second order smallscale fluctuations can mimic an accelerating universe.

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THE PECULIAR VELOCITIES OF LOCAL TYPE Ia SUPERNOVAE AND THEIR IMPACT ON COSMOLOGY


 We quantify the effect of supernova Type Ia peculiar velocities on the derivation of cosmological parameters. The published distant and local Ia SNe used for the Supernova Legacy Survey first-year cosmology report form the sample for this study. While previous work has assumed that the local SNe are at rest in the CMB frame (the No Flow assumption), we test this assumption by applying peculiar velocity corrections to the local SNe using three different flow models. The models are based on the IRAS PSCz galaxy redshift survey, have varying = 0.6m /b, and reproduce the Local Group motionin the CMB frame. These datasets are then fit for w, m, and using flatne

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Measuring cosmic bulk flows with Type Ia Supernovae from the Nearby Supernova Factory


  ABSTRACT Context. Our Local Group of galaxies appears to be moving relative to the Cosmic Microwave Background with the source of thepeculiar motion still uncertain. While in the past this has been studied mostly using galaxies as distance indicators, the weight oftype Ia supernovae (SNe Ia) has increased recently with the continuously improving statistics of available low-redshift supernovae.Aims. We measured the bulk flow in the nearby universe (0:015 < z < 0:1) using 117 SNe Ia observed by the Nearby SupernovaFactory, as well as the Union2 compilation of SN Ia data already in the literature.Methods. The bulk flow velocity was determined from SN data binned in

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پاور پوینت (اسلاید) تمرینات اصلاح کننده لوردوز (Advanced Corrective Exercises Hyper Lordosis)


 با سلام
فایل تمرینات اصلاح کننده لوردوز (Advanced Corrective Exercises Hyper Lordosis) یک پاورپوینت بسیار عالی در 118 اسلاید می باشد این PowerPoint بر اساس استاندارد های اصلی طراحی پاورپوینت آماده و تنظیم شده است؛ این فایل دارای طراحی بسیار عالی و چشم نواز می باشد.
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The Luminosity Distance in Perturbed FLRW Spacetimes


ABSTRACTWe derive an expression for the luminosity distance in FLRW spacetimes affectedby scalar perturbations. Our expression is complete to linear order and is expressedentirely in terms of standard cosmological parameters and observational quantities.Weillustrate the result by calculating the RMS scatter in the usual luminosity distancein flat (m) = (1.0, 0.0) and (0.3, 0.7) cosmologies. In both cases the scatter isappreciable at high redshifts, and rises above 11% at z = 2, where it may be thedominant noise term in the Hubble diagram based on SN Ia.

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آشفتگی در باد خورشیدی - Turbulence in the Solar Wind


توضیحات : This book provides an overview of solar wind turbulence from both the theoretical and observational perspective. It argues that the interplanetary medium offers the best opportunity to directly study turbulent fluctuations in collisionless plasmas.  In fact, during expansion, the solar wind evolves towards a state characterized by large-amplitude fluctuations in all observed parameters, which resembles, at least at large scales, the well-known hydrodynamic turbulence.This text starts with historical references to past observations and experiments on turbulent flows. It then introduces the Navier-Stokes equations for a magnetized plasma whose low-frequency turbulence evolution is described within t

ادامه مطلب  
Supernovae as seen by off-center observers in a local void


Abstract. Inhomogeneous universe models have been proposed as an alternativeexplanation for the apparent acceleration of the cosmic expansion that does not requiredark energy. In the simplest class of inhomogeneous models, we live within a large,spherically symmetric void. Several studies have shown that such a model can bemade consistent with many observations, in particular the redshift–luminosity distancerelation for type Ia supernovae, provided that the void is of Gpc size and that we liveclose to the center. Such a scenario challenges the Copernican principle that we donot occupy a special place in the universe. We use the first-year Sloan Digital SkySurvey-II supernova search data set as well as the

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