The 6dF Galaxy Survey: Mass and Motions in the Local Universe

2005 ◽  
Vol 216 ◽  
pp. 180-189
Author(s):  
Matthew Colless ◽  
Heath Jones ◽  
Lachlan Campbell ◽  
Daniel Burkey ◽  
Andy Taylor ◽  
...  
Keyword(s):  
Cosmological Parameters ◽  
Relevant Information ◽  
Local Universe ◽  
Distortion Parameter ◽  
Peculiar Velocities ◽  
Wide Range ◽  
Data Release ◽  
The Galaxy ◽  
The Status ◽  
Space Distortion

The 6dF Galaxy Survey will provide 167 000 redshifts and about 15000 peculiar velocities for galaxies over most of the southern sky out to about cz = 30000 km s--1. The survey is currently almost half complete, with the final observations due in mid-2005. An initial data release was made public in December 2002; the first third of the dataset will be released at the end of 2003, with the remaining thirds being released at the end of 2004 and 2005. The status of the survey, the survey database and other relevant information can be obtained from the 6dFGS web site at http://www.mso.anu.edu.au/6dFGS.In terms of constraining cosmological parameters, combining the 6dFGS redshift and peculiar velocity surveys will allow us to: (1) break the degeneracy between the redshift-space distortion parameter β = Ω0.6m/b and the galaxy-mass correlation parameter rg; (2) measure the four parameters Ag, Γ, β and rg with precisions of between 1% and 3%; (3) measure the variation of rg and b with scale to within a few percent over a wide range of scales.

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 The Alcock Paczynski test with voids in 21 cm intensity field

2020 ◽  
Vol 499 (1) ◽  
pp. 587-596
Author(s):  
Takao Endo ◽  
Hiroyuki Tashiro ◽  
Atsushi J Nishizawa
Keyword(s):  
Parameter Estimation ◽  
Linear Prediction ◽  
Real Space ◽  
Line Of Sight ◽  
Peculiar Velocities ◽  
The Galaxy ◽  
Intensity Field ◽  
Space Distortion ◽  
Intensity Map ◽  
Free Parameters

ABSTRACT Feasibility of the Alcock Paczynski (AP) test by stacking voids in the 21 cm line intensity field is presented. We analyse the IllustrisTNG simulation to obtain the 21 cm signal map. We then randomly distribute particles depending on the 21 cm intensity field to find voids by using publicly available code, VIDE. As in the galaxy clustering, the shape of the stacked void in the 21 cm field is squashed along the line of sight due to the peculiar velocities in redshift space, although it becomes spherical in real space. The redshift-space distortion for the stacked void weakly depends on redshift and we show that the dependency can be well described by the linear prediction, with the amplitude of the offset being free parameters. We find that the AP test using the stacked voids in a 21 cm intensity map is feasible and the parameter estimation on Ωm and w is unbiased.

scholarly journals Joint growth-rate measurements from redshift-space distortions and peculiar velocities in the 6dF Galaxy Survey

2020 ◽  
Vol 494 (3) ◽  
pp. 3275-3293 ◽  
Author(s):  
Caitlin Adams ◽  
Chris Blake
Keyword(s):  
Growth Rate ◽  
Large Scale ◽  
Likelihood Method ◽  
Distortion Parameter ◽  
Peculiar Velocities ◽  
Cross Covariance ◽  
Space Distortion ◽  
Standard Cosmological Model ◽  
Parameter Constraints ◽  
Field Galaxy

ABSTRACT We present a new model for the cross-covariance between galaxy redshift-space distortions and peculiar velocities. We combine this with the autocovariance models of both probes in a fully self-consistent, maximum-likelihood method, allowing us to extract enhanced cosmological parameter constraints. When applying our method to the 6-degree Field Galaxy Survey (6dFGS), our constraint on the growth rate of structure is $f\sigma _8 = 0.384 \pm 0.052 \rm {(stat)} \pm 0.061 \rm {(sys)}$ and our constraint for the redshift-space distortion parameter is $\beta = 0.289^{+0.044}_{-0.043} \rm {(stat)} \pm 0.049 \rm {(sys)}$. We find that the statistical uncertainty for the growth rate of structure is reduced by 64 per cent when using the complete covariance model compared to the redshift-space distortion autocovariance model and 50 per cent when compared to using the peculiar-velocity autocovariance model. Our constraints are consistent with those from the literature on combining multiple tracers of large-scale structure, as well as those from other 6dFGS analyses. Our measurement is also consistent with the standard cosmological model.

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 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.

Cosmological Parameters from the 2dF Galaxy Redshift Survey

2005 ◽  
Vol 201 ◽  
pp. 158-167
Author(s):  
Matthew Colless
Keyword(s):  
Precise Measurement ◽  
Cosmological Parameters ◽  
Current Status ◽  
Low Density ◽  
Distortion Parameter ◽  
Preliminary Results ◽  
Redshift Survey ◽  
Space Distortion ◽  
Galaxy Redshift

This paper describes the goals, current status and some preliminary results from the 2dF Galaxy Redshift Survey. In particular we present the most precise measurement to date of the redshift-space distortion parameter, β ≡ Ω0.6/b = 0.39 ± 0.05. Combined with recent CMB anisotropy measurements, our results strongly favour a low-density universe.

The 6dFGS peculiar velocity field

2012 ◽  
Vol 8 (S289) ◽  
pp. 269-273
Author(s):  
Christopher M. Springob ◽  
Christina Magoulas ◽  
Matthew Colless ◽  
D. Heath Jones ◽  
Lachlan Campbell ◽  
...  
Keyword(s):  
Velocity Field ◽  
Gaussian Model ◽  
Density Field ◽  
Bulk Flow ◽  
Bayesian Probability ◽  
Distortion Parameter ◽  
Peculiar Velocity ◽  
Peculiar Velocities ◽  
Redshift Survey ◽  
Space Distortion

AbstractThe 6dF Galaxy Survey (6dFGS) is an all-southern-sky galaxy survey, including 125,000 redshifts and a Fundamental Plane (FP) subsample of 10,000 peculiar velocities. This makes 6dFGS the largest peculiar-velocity sample to date. We have fitted the FP with a tri-variate Gaussian model using a maximum-likelihood approach, and derive the Bayesian probability distribution of the peculiar velocity for each of the 10,000 galaxies. We fit models of the velocity field, including comparisons to the field predicted from the redshift-survey density field, to derive the values of the redshift-space distortion parameter β, the bulk flow and the residual bulk flow in excess of that predicted from the density field. We compare these results to those derived by other authors and discuss the cosmological implications.

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 completed SDSS-IV extended baryon oscillation spectroscopic survey: geometry and growth from the anisotropic void–galaxy correlation function in the luminous red galaxy sample

2020 ◽  
Vol 499 (3) ◽  
pp. 4140-4157
Author(s):  
Seshadri Nadathur ◽  
Alex Woodfinden ◽  
Will J Percival ◽  
Marie Aubert ◽  
Julian Bautista ◽  
...  
Keyword(s):  
Correlation Function ◽  
High Redshift ◽  
Sloan Digital Sky Survey ◽  
Reconstruction Method ◽  
Distance Ratio ◽  
Galaxy Clustering ◽  
Data Release ◽  
The Galaxy ◽  
Galaxy Sample ◽  
Space Distortion

ABSTRACT We present an analysis of the anisotropic redshift-space void–galaxy correlation in configuration space using the Sloan Digital Sky Survey extended Baryon Oscillation Spectroscopic Survey (eBOSS) Data Release 16 luminous red galaxy (LRG) sample. This sample consists of LRGs between redshifts 0.6 and 1.0, combined with the high redshift z > 0.6 tail of the Baryon Oscillation Spectroscopic Survey Data Release 12 CMASS sample. We use a reconstruction method to undo redshift-space distortion (RSD) effects from the galaxy field before applying a watershed void-finding algorithm to remove bias from the void selection. We then perform a joint fit to the multipole moments of the correlation function for the growth rate fσ8 and the geometrical distance ratio DM/DH, finding $f\sigma _8(z_\rm {eff})=0.356\pm 0.079$ and $D_M/D_H(z_\rm {eff})=0.868\pm 0.017$ at the effective redshift $z_\rm {eff}=0.69$ of the sample. The posterior parameter degeneracies are orthogonal to those from galaxy clustering analyses applied to the same data, and the constraint achieved on DM/DH is significantly tighter. In combination with the consensus galaxy BAO and full-shape analyses of the same sample, we obtain fσ8 = 0.447 ± 0.039, DM/rd = 17.48 ± 0.23, and DH/rd = 20.10 ± 0.34. These values are in good agreement with the ΛCDM model predictions and represent reductions in the uncertainties of $13{{\ \rm per\ cent}}$, $23{{\ \rm per\ cent}}$, and $28{{\ \rm per\ cent}}$, respectively, compared to the combined results from galaxy clustering, or an overall reduction of 55 per cent in the allowed volume of parameter space.

РУССКИЙ ЯЗЫК – ЯЗЫК ВЫСШЕГО ОБРАЗОВАНИЯ В КГМА

2020 ◽  
pp. 50-53
Author(s):  
Г. Кульбаева
Keyword(s):  
Russian Language ◽  
Educational Activity ◽  
Official Language ◽  
Main Motivation ◽  
Language Functioning ◽  
Teaching Language ◽  
Medical Academy ◽  
Wide Range ◽  
The Status ◽  
The Russian Language

Аннотация. В статье рассматривается вопрос о функционировании русского языка в образовательном пространстве КГМА. Большое место в работе занимает роль русского языка в учебной деятельности студентов-медиков. Мотивацией к изучению именно, русского языка являются следующие факторы: статус официального языка; возможность привлечь внимание широкого круга специалистов к своим исследованиям; понимание престижности русского языка. В статье нашли отражение различные формы работы по расширению сферы использования русского языка в медицинской академии. В работе уделено внимание и профильным учебным пособиям, разработанным автором статьи. Анализ некоторых заданий позволяет констатировать тот факт, что содержание пособии определено через компетенции, одной из которых является языковая. Ключевые слова:язык обучения, фундаментальные науки, соматические ФЕ, компетентностная основа, профессиональная направленность, жаргонная лексика. Аннотация. Макалада КММАнын билим берүү мейкиндеги орус тилин өздөштүү маселеси каралат. Орус тили студент-медиктердин окуу ишмердигинде чоң роль ойнойт. Расмий тил статусу, өз изилдөөлөрүнө көпчүлүк адистердин көңүлүн буруу мүмкүнчүлүгү, орус тилинин баркын түшүнүү, өзгөчөлөп билүүгө далил болуп эсептелет. Макалада медициналык академияда орус тили колдонуу чөйрөсүн кеңейтүү боюнча иштөөнү ар кандай формалары көрсөтүлгөн. Эмгекте макаланын автору иштеп чыккан адистик окуу колдонмолорго да көңул бурулган. Кээ бир тапшырмалардын анализи колдонмонун мазмуну компетенция, анын бирөөсү тил аркылуу аныкталганын факт катары көрсөтүүгө мүмкүндүк түзөт. Түйүндүү сөздөр: фундаменталдык илимдер, соматикалык фразеологизмдер, компетенттик негиз, профессионалдык багытталыш, жаргондук лексика. Summary. The article discusses the Russian language functioning in the of the KSMA’s educational space. Russian language plays a big role in the educational activity of the medical students. The main motivation of learning the Russian language has the following points: the status of the official language; the opportunity to attract the attention of a wide range of specialists to their research; understanding of the prestige of the Russian language. The article reflected various forms of work to expand the scope of the use of the Russian language at the medical academy. The work focuses on specialized textbooks developed by the author of the article. An analysis of some tasks allows us to state the fact that the content of the manual is determined through competencies, one of which is the language. Key words: teaching language, fundamental sciences, somatic phraseological unit, slang vocabulary.

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