How empty are the voids in the universe?

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SUMMARY

The current measured density contrast inside cosmological voids of approximately 30 Mpc radius shows that the matter density, both visible and dark, drops to about 20% of the average, resulting in a density contrast of -0.80, as established in L. da Costa's 1996 paper published in the Astrophysical Journal. Recent inquiries into updated measurements have highlighted the need for actual observational data rather than N-body simulations, which have not directly detected the matter in these voids. The discussion references two articles that focus on voids but do not provide the comprehensive density measurements sought.

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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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