Constrained simulations of the local universe: II. The nature of the local Hubble flow

Abstract

Using a suite of N-body simulations in different Cold Dark Matter (CDM) scenarios, with cosmological constant (\LCDM) and without (OCDM, SCDM), we study the Hubble flow (\sigh) in Local Volumes (LV) around Local Group (LG) like objects found in these simulations, and compare the numerical results with the most recent observations. We show that \LCDM and OCDM models exhibit the same behavior of \sigh. Hence, we demonstrate that the observed coldness of the Hubble flow is not likely to be a manifestation of the dark energy, contrary to previous claims. The coldness does not constitute a problem by itself but it poses a problem to the standard \LCDM model only if the mean density within the Local Volume is greater than twice the mean matter cosmic density. The lack of blueshifted galaxies in the LV, outside of the LG can be considered as another manifestation of the coldness of the flow. Finally, we show that the main dynamical parameter that affects the coldness of the flow is the relative isolation of the LG, and the absence of nearby Milky Way like objects within a distance of about $3\mpc$.

13 pages, 8 figures, 5 tables. Submitted to MNRAS

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• Dark energy domination in the Virgocentric flow
• Halo based reconstruction of the cosmic mass density field
• Dark energy domination in the local flow of giant galaxies
• On the coldness of the local Hubble flow: the role of baryons
• The Velocity Field Around Groups of Galaxies