scholarly journals Maximum-likelihood fitting of the 6dFGS peculiar velocities

2012 ◽  
Vol 8 (S289) ◽  
pp. 402-405 ◽  
Author(s):  
Christina Magoulas ◽  
Christopher Springob ◽  
Matthew Colless ◽  
D. Heath Jones ◽  
Lachlan Campbell ◽  
...  
Keyword(s):  
Bayesian Model ◽  
Cosmological Parameters ◽  
Matter Distribution ◽  
Data Set ◽  
Fundamental Plane ◽  
Peculiar Velocity ◽  
Peculiar Velocities ◽  
Galaxy Distribution ◽  
The Galaxy ◽  
Redshift Survey

AbstractWe develop a robust Bayesian model to derive peculiar velocities and Fundamental Plane (FP) distances for a subsample of 9000 galaxies from the 6dF Galaxy Survey (6dFGS). These galaxies form the basis of 6dFGSv, the largest and most uniform galaxy peculiar-velocity sample to date. We perform a Bayesian analysis of the data set as a whole, determining cosmological parameters from the peculiar-velocity field (e.g., fitting β and the bulk flow), by comparing to the field predicted from the redshift survey and assuming that the galaxy distribution traces the matter distribution.

scholarly journals The redshift-space momentum power spectrum – I. Optimal estimation from peculiar velocity surveys

2019 ◽  
Vol 487 (4) ◽  
pp. 5209-5234 ◽  
Author(s):  
Cullan Howlett
Keyword(s):  
Power Spectrum ◽  
Measurement Errors ◽  
Cosmological Parameters ◽  
Power Spectra ◽  
Optimal Estimation ◽  
Peculiar Velocity ◽  
Optimal Weights ◽  
Peculiar Velocities ◽  
Redshift Surveys ◽  
The Galaxy

Abstract Low redshift surveys of galaxy peculiar velocities provide a wealth of cosmological information. We revisit the idea of extracting this information by directly measuring the redshift-space momentum power spectrum from such surveys. We provide a comprehensive theoretical and practical framework for estimating and fitting this from data, analogous to well-understood techniques used to measure the galaxy density power spectrum from redshift surveys. We formally derive a new estimator, which includes the effects of shot noise and survey geometry; we evaluate the variance of the estimator in the Gaussian regime; we compute the optimal weights for the estimator; we demonstrate that the measurements are Gaussian distributed, allowing for easy extraction of cosmological parameters; and we explore the effects of peculiar velocity (PV) measurement errors. We finish with a proof-of-concept using realistic mock galaxy catalogues, which demonstrates that we can measure and fit both the redshift-space galaxy density and momentum power spectra from PV surveys and that including the latter substantially improves our constraints on the growth rate of structure. We also provide theoretical descriptions for modelling the non-linear redshift-space density and momentum power spectrum multipoles, and forecasting the constraints on cosmological parameters using the Fisher information contained in these measurements for arbitrary weights. These may be useful for measurements of the galaxy density power spectrum even in the absence of peculiar velocities.

scholarly journals Measuring the cosmic bulk flow with 6dFGSv

2014 ◽  
Vol 11 (S308) ◽  
pp. 336-339 ◽  
Author(s):  
Christina Magoulas ◽  
Christopher Springob ◽  
Matthew Colless ◽  
Jeremy Mould ◽  
John Lucey ◽  
...  
Keyword(s):  
Velocity Field ◽  
Large Scale ◽  
Cosmological Parameters ◽  
Distortion Parameter ◽  
Peculiar Velocity ◽  
Peculiar Velocities ◽  
Redshift Surveys ◽  
Luminous Matter ◽  
The Galaxy ◽  
Space Distortion

AbstractWhile recent years have seen rapid growth in the number of galaxy peculiar velocity measurements, disagreements remain about the extent to which the peculiar velocity field - a tracer of the large-scale distribution of mass - agrees with both ΛCDM expectations and with velocity field models derived from redshift surveys. The 6dF Galaxy Survey includes peculiar velocities for nearly 9 000 early-type galaxies (6dFGSv), making it the largest and most homogeneous galaxy peculiar velocity sample to date. We have used the 6dFGS velocity field to determine the amplitude and scale of large-scale cosmic flows in the local universe and test standard cosmological models. We also compare the galaxy density and peculiar velocity fields to establish the distribution of dark and luminous matter and better constrain key cosmological parameters such as the redshift-space distortion parameter.

scholarly journals Structure and kinematics of the Bootes filament

2014 ◽  
Vol 11 (S308) ◽  
pp. 187-192
Author(s):  
O. Nasonova ◽  
I. Karachentsev ◽  
V. Karachentseva
Keyword(s):  
Dark Matter ◽  
Stellar Mass ◽  
Average Density ◽  
Virgo Cluster ◽  
Galaxy Groups ◽  
Peculiar Velocities ◽  
Galaxy Distribution ◽  
The Galaxy ◽  
Virial Mass ◽  
Individual Distance

AbstractBootes filament of galaxies is a dispersed chain of groups residing on sky between the Local Void and the Virgo cluster. We consider a sample of 361 galaxies inside the sky area of RA = 13h0...18h.5 and Dec = .5°... + 10° with radial velocities VLG < 2000 km/s to clarify its structure and kinematics. In this region, 161 galaxies have individual distance estimates. We use these data to draw the Hubble relation for galaxy groups, pairs as well as the field galaxies, and to examine the galaxy distribution on peculiar velocities. Our analysis exposes the known Virgo-centric infall at RA < 14h and some signs of outflow from the Local Void at RA > 17h. According to the galaxy grouping criterion, this complex contains the members of 13 groups, 11 pairs and 140 field galaxies. The most prominent group is dominated by NGC 5846. The Bootes filament contains the total stellar mass of 2.7 ×1012M⊙ and the total virial mass of 9.07×1013M⊙, having the average density of dark matter to be Ωm = 0.09, i.e. a factor three lower than the global cosmic value.

scholarly journals Multiwavelength cross-correlation analysis of the simulated cosmic web

2020 ◽  
Vol 494 (4) ◽  
pp. 5603-5618 ◽  
Author(s):  
C Gheller ◽  
F Vazza
Keyword(s):  
Faraday Rotation ◽  
Cross Correlation ◽  
Future Generation ◽  
Matter Distribution ◽  
X Ray ◽  
Galaxy Distribution ◽  
Cross Correlation Analysis ◽  
The Galaxy ◽  
The Cross ◽  
Diffuse Matter

ABSTRACT We used magnetohydrodynamical cosmological simulations to investigate the cross-correlation between different observables (i.e. X-ray emission, Sunyaev–Zeldovich (SZ) signal at 21 cm, H i temperature decrement, diffuse synchrotron emission, and Faraday Rotation) as a probe of the diffuse matter distribution in the cosmic web. We adopt a uniform and simplistic approach to produce synthetic observations at various wavelengths, and we compare the detection chances of different combinations of observables correlated with each other and with the underlying galaxy distribution in the volume. With presently available surveys of galaxies and existing instruments, the best chances to detect the diffuse gas in the cosmic web outside of haloes is by cross-correlating the distribution of galaxies with SZ observations. We also find that the cross-correlation between the galaxy network and the radio emission or the Faraday Rotation can already be used to limit the amplitude of extragalactic magnetic fields, well outside of the cluster volume usually explored by existing radio observations, and to probe the origin of cosmic magnetism with the future generation of radio surveys.

scholarly journals Large-scale peculiar velocities through the galaxy luminosity function at z ~ 0.1

2014 ◽  
Vol 11 (S308) ◽  
pp. 332-335
Author(s):  
Martin Feix ◽  
Adi Nusser ◽  
Enzo Branchini
Keyword(s):  
Velocity Field ◽  
Large Scale ◽  
Zero Point ◽  
Peculiar Velocity ◽  
Peculiar Velocities ◽  
The Galaxy ◽  
Linear Velocity Field ◽  
Density Perturbations ◽  
Velocity Moments ◽  
Galaxy Luminosity Function

AbstractPeculiar motion introduces systematic variations in the observed luminosity distribution of galaxies. This allows one to constrain the cosmic peculiar velocity field from large galaxy redshift surveys. Using around half a million galaxies from the SDSS Data Release 7 at z ~ 0.1, we demonstrate the applicability of this approach to large datasets and obtain bounds on peculiar velocity moments and σ8, the amplitude of the linear matter power spectrum. Our results are in good agreement with the ΛCDM model and consistent with the previously reported ~ 1% zero-point tilt in the SDSS photometry. Finally, we discuss the prospects of constraining the growth rate of density perturbations by reconstructing the full linear velocity field from the observed galaxy clustering in redshift space.

The Optical Redshift Survey: Sample Selection and the Galaxy Distribution

1995 ◽  
Vol 446 ◽  
pp. 457 ◽  
Author(s):  
Basilio X. Santiago ◽  
Michael A. Strauss ◽  
Ofer Lahav ◽  
Marc Davis ◽  
Alan Dressler ◽  
...  
Keyword(s):  
Sample Selection ◽  
Galaxy Distribution ◽  
The Galaxy ◽  
Redshift Survey ◽  
Survey Sample

scholarly journals The peculiar velocity field up to z ∼ 0.05 by forward-modelling Cosmicflows-3 data

2019 ◽  
Vol 488 (4) ◽  
pp. 5438-5451 ◽  
Author(s):  
R Graziani ◽  
H M Courtois ◽  
G Lavaux ◽  
Y Hoffman ◽  
R B Tully ◽  
...  
Keyword(s):  
Velocity Field ◽  
Initial Conditions ◽  
Selection Function ◽  
Data Sets ◽  
Forward Modelling ◽  
Local Universe ◽  
Peculiar Velocity ◽  
Peculiar Velocities ◽  
The Galaxy ◽  
Distance Indicators

Abstract A hierarchical Bayesian model is applied to the Cosmicflows-3 catalogue of galaxy distances in order to derive the peculiar velocity field and distribution of matter within z ∼ 0.054. The model assumes the ΛCDM model within the linear regime and includes the fit of the galaxy distances together with the underlying density field. By forward modelling the data, the method is able to mitigate biases inherent to peculiar velocity analyses, such as the Homogeneous Malmquist bias or the lognormal distribution of peculiar velocities. The statistical uncertainty on the recovered velocity field is about 150 km s−1 depending on the location, and we study systematics coming from the selection function and calibration of distance indicators. The resulting velocity field and related density fields recover the cosmography of the Local Universe which is presented in an unprecedented volume of our Universe 10 times larger than previously reached. This methodology opens the doors to reconstruction of initial conditions for larger and more accurate constrained cosmological simulations. This work is also preparatory to larger peculiar velocity data sets coming from Wallaby, TAIPAN, or LSST.

scholarly journals Optical Redshift Surveys

1992 ◽  
Vol 9 ◽  
pp. 681-683
Author(s):  
L. Nicolaci da Costa
Keyword(s):  
Large Scale ◽  
Current Status ◽  
Redshift Surveys ◽  
Galaxy Distribution ◽  
The Galaxy ◽  
Redshift Survey ◽  
Different Depths ◽  
Source Of Information ◽  
The Universe

Redshift surveys of galaxies have been over the past decade the major source of information for studies of the large-scale structure of the Universe. Following the completion of the original CfA Redshift Survey, several groups have joined the endeavor, probing different regions of the sky to different depths in a remarkable long-term effort to study the nature of the galaxy distribution and its statistical properties at different scales. Here I summarize the current status of the ongoing surveys drawn from optical galaxy catalogs. The review is not intended to be complete but rather to demonstrate the vitality of the area and to point out that exciting new data should be forthcoming in the next few years.

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