How empty are the voids in the universe?

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Discussion Overview

The discussion revolves around the measured density contrast within cosmological voids, specifically those with a radius of about 30 Mpc. Participants are seeking updated empirical data on the matter density in these voids, including both visible and dark matter, as opposed to simulations.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant references a paper by L. da Costa that reports a density contrast of -0.80 in nearby voids, indicating a matter density of about 20% of the average.
  • Another participant provides links to two more recent papers, but these focus on simulations and underdensity of visible matter rather than total matter density.
  • A participant expresses a need for actual measurements rather than simulations, emphasizing the importance of including both visible and dark matter in the analysis of voids.
  • Contact information for L. da Costa is shared as a potential resource for further inquiry into the topic.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the availability of recent empirical measurements of density in cosmological voids, with some expressing a preference for actual data over simulations.

Contextual Notes

There is a noted distinction between the underdensity of visible matter and the total underdensity that includes dark matter, which remains unresolved in the discussion.

smallphi
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What is the current measured density contrast inside the cosmological voids of radius about 30 Mpc? By measured I mean somebody constructed a density map based on peculiar velocities map or weak lensing.

I've read a Paper by L. da Costa - Astrophysical Journal 468, L5, 1996 - that constructed a density map of our neighbourhood (radius about 100 Mpc) based on measured peculiar velocities of galaxies. According to the density contours the matter (visible and dark) density inside the voids around us drops to about 20% of the average i.e. density contrast = -0.80.

Has anyone seen more recent paper that measure the matter density in the voids?
 
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Thanks for the articles. What I had in mind though was something like an update of the article I cited since its more than 10 years old.

The first article you posted talks about N-body simmulations of dark matter - I need actual measurements not simmulations of something that hasn't been detected directly yet.

The second article talks about voids in the Sloan Digital Sky Survey but there they talk about the underdensity of galaxies in voids, i.e. underdensity of visible matter while I'm interested in the total underdensity including visible and dark matter.
 

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