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Cosmological Constraints from Type Ia Supernovae Peculiar Velocity Measurements


The first compelling evidence that the Universe is undergoinga period of accelerated expansion was providedby observations of Type Ia supernovae (SNe) [1, 2].The data from many current [3, 4, 5] and near future[6, 7, 8, 9] surveys should eventually constrain the effectivedark energy equation of state to better than 10%.Density inhomogeneities cause the SNe to deviate fromthe Hubble flow, as gravitational instability leads to matterflowing out of under-densities and into over-densities.These “peculiar velocities” (PVs) lead to an increasedscatter in the Hubble diagram, of which several studieshave been made [10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20,21, 22]. When combining low a

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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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The peculiar velocity field: constraining the tilt of the Universe


A large bulk flow, which is in tension with the Lambda Cold Dark Matter (CDM) cosmologicalmodel, has been observed. In this paper, we provide a physically plausible explanation of this bulkflow, based on the assumption that some fraction of the observed dipole in the cosmic microwavebackground is due to an intrinsic fluctuation, so that the subtraction of the observed dipole leads toa mismatch between the cosmic microwave background (CMB) defined rest frame and the matterrest frame. We investigate a model that takes into account the relative velocity (hereafter the tiltedvelocity) between the two frames, and develop a Bayesian statistic to explore the likelihood of thistilted velocity.By studying variou

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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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Measuring our peculiar velocity on the CMB with high-multipole


Our peculiar velocity with respect to the CMB rest frame is known to induce a large dipole inthe CMB. However, the motion of an observer has also the effect of distorting the anisotropies atall scales, as shown by Challinor and Van Leeuwen (2002), due to aberration and Doppler effects.We propose to measure independently our local motion by using off-diagonal two-point correlationfunctions for high multipoles. We study the observability of the signal for temperature and polarizationanisotropies. We point out that Planck can measure the velocity with an error of about30% and the direction with an error of about 20. This method constitutes a cross-check, which canbe useful to verify that our CMB dipole is due

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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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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

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Principal Component Analysis of Modified Gravity using Weak Lensing and Peculiar Velocity Measurements


Abstract. We perform a principal component analysis to assess ability of future observationsto measure departures from General Relativity in predictions of the Poisson and anisotropyequations on linear scales. In particular, we focus on how the measurements of redshiftspacedistortions (RSD) observed from spectroscopic galaxy redshift surveys will improve theconstraints when combined with lensing tomographic surveys. Assuming a Euclid-like galaxyimaging and redshift survey, we find that adding the 3D information decreases the statisticaluncertainty by a factor between 3 and 10 compared to the case when only observables fromlensing tomographic surveys are used. We also

ادامه مطلب  
Cosmic Bulk Flow and the Local Motion from Cosmicflows-2


Full sky surveys of peculiar velocity are arguably the best way to map the large scalestructure (LSS) out to distances of a few100 h????1Mpc. Using the largest and most accurateever catalog of galaxy peculiar velocities Cosmicflows-2, the LSS has been reconstructed bymeans of the Wiener filter (WF) and constrained realizations (CRs) assuming as a Bayesianprior model the CDM model with the WMAP inferred cosmological parameters. The presentpaper focuses on studying the bulk flow of the local flow field, defined as the mean velocityof top-hat spheres with radii ranging out to R = 500 h????1Mpc. The estimated LSS, in general,and the bulk flow, in particular, are determined by the tension between the observational dat

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The Velocity Field from Type Ia Supernovae Matches the Gravity Field from Galaxy Surveys


 We compare the peculiar velocities of nearby SNe Ia with those predicted bythe gravity fields of full sky galaxy catalogs. The method provides a powerfultest of the gravitational instability paradigm and strong constraints on the density parameter 0.6/b. For 24 SNe Ia within 10,000 km s−1, we find theobserved SNe Ia peculiar velocities are well modeled by the predictions derivedfrom the 1.2 Jy IRAS survey and the Optical Redshift Survey (ORS). Our bestis 0.4 from IRAS, and 0.3 from the ORS, with > 0.7 and < 0.15 ruledout at 95% confidence levels from the IRAS comparison. Bootstrap resamplingtests show these results to be robust in the mean and in its error. The

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