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#cosmicflows

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Public
Daniel Pomarède

Wowzer! Map of cosmic flows, by yours truly, makes it to the cover of the Nature Astronomy journal.

"Galaxies from
wherever flock
together"

I'm no poet, but could this be a Haiku?

nature.com/natastron/volumes/8

Credits:
Image: Daniel Pomarède, Institut de Recherche sur les Lois Fondamentales de l’Univers, CEA, Université Paris-Saclay.
Cover design: Bethany Vukomanovic.

A cover of the Nature Astronomy journal, dated December 2024, Volume 8, issue number 12, featuring a three-dimensional visualization of the cosmic velocity field inferred from the Cosmicflows-4 catalog of galaxies' distances and velocities. This map spans two billion lightyears from top to bottom. The velocity field is mapped by means of tens of thousands of very thin streamlines, seeded at the positions of the catalog's galaxies. Streamlines are shown white and semi-transparent, against a black background. They exhibit a very complex pattern with multiple attractors, seen as points of convergence of the lines. A text reads Galaxies from wherever flock together.
#Cosmology#Galaxies#Astronomy
Public
Daniel Pomarède

Advanced data shed light on gravitational basins of attraction that shape the movement of galaxies

A new study has mapped out the gravitational basins of attraction in the local universe, offering fresh insights into the large-scale cosmic structures that shape the movement of galaxies. The study has been published in #NatureAstronomy

phys.org/news/2024-09-advanced

Phys.org · Advanced data shed light on gravitational basins of attraction that shape the movement of galaxiesBy Hebrew University of Jerusalem
#Cosmology#Cosmicflows#galaxies
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Daniel Pomarède

Meet the Laniakea supercluster

nature.com/articles/513041a

NatureMeet the Laniakea supercluster - NatureThe Milky Way is a member of the Local Group of galaxies. Now have sufficient data on the distances and motions of galaxies to be able to describe a much larger level of organization in our corner of the Universe — a supercluster 160 megaparsecs across and containing 1017 solar masses. Brent Tully et al. use a new catalogue of 'peculiar velocities', line-of-sight departures from cosmic expansion caused by gravitational perturbation, to develop a map representing the distribution of matter. They identify a 'home' supercluster that they name Laniakea — from the Hawaiian lani and akea ('heaven' and 'spacious'). It includes the Virgo cluster, the Norma, Hydra and Centaurus clusters (also known as the Great Attractor), the Pavo-Indus filament and a number of voids.
#Laniakea#supercluster#galaxies
Public
Daniel Pomarède

#PaperDay

The large scale velocity field from the Cosmicflows-4 data

arxiv.org/abs/2311.01340

arXiv.orgThe large scale velocity field from the Cosmicflows-4 dataThe reconstruction of the large scale velocity field from the grouped Cosmicflows-4 (CF4) database is presented. The lognormal bias of the inferred distances and velocities data is corrected by the Bias Gaussianization correction (BGc) scheme, and the linear density and velocity fields are reconstructed by means of the Wiener filter (WF) and constrained realizations (CRs) algorithm. These tools are tested against a suite of random and constrained Cosmicflows-3-like mock data. The CF4 data consists of 3 main subsamples - the 6dFGS and the SDSS data - and the `others'. The individual contributions of the subsamples have been studied. The quantitative analysis of the velocity field is done mostly by the mean overdensity ($Δ_L(R)$) and the bulk velocity ($V_{\mathrm{bulk}}(R)$) profiles of the velocity field out to $300\, h^{-1}{\rm Mpc}$. The $V_{\mathrm{bulk}}(R)$ and $Δ_{\mathrm L}(R)$ profiles of the CF4 data without its 6dFGS component are consistent with the cosmic variance to within $1σ$. The 6dFGS sample dominates the $V_{\mathrm{bulk}}$ ($Δ_{\mathrm L}$) profile beyond $\sim120\, h^{-1}{\rm Mpc}$, and drives it to roughly a $3.4σ$ ($-1.9σ$) excess (deficiency) relative to the cosmic variance at $R\sim250\ (190)\ \, h^{-1}{\rm Mpc}$. The excess in the amplitude of $V_{\mathrm{bulk}}$ is dominated by its Supergalactic X component, roughly in the direction of the Shapley Concentration. The amplitude and alignment of the inferred velocity field from the CF4 data is at $\sim(2\,-\,3)\,σ$ discrepancy with respect to the $Λ$CDM model. Namely, it is somewhat atypical but yet there is no compelling tension with the model.
#cosmology#cosmography#cosmicflows
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