Independent evidence found for BAO and more in Lya-forest from quasars
6 Feb 2013 10:14:18 UTC
Topic 196790
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Hallo!
See here http://arxiv.org/pdf/1211.2616v1.pdf
ABSTRACT
We report a detection of the baryon acoustic oscillation (BAO) feature in the three-dimensional correlation function of the transmitted
flux fraction in the Lyα forest of high-redshift quasars. The study uses 48,640 quasars in the redshift range 2.1 ≤ z ≤ 3.5 from the
Baryon Oscillation Spectroscopic Survey (BOSS) of the third generation of the Sloan Digital Sky Survey (SDSS-III). At a mean
redshift z = 2.3, we measure the monopole and quadrupole components of the correlation function for separations in the range
20h−1Mpc < r < 200h−1Mpc. A peak in the correlation function is seen at a separation equal to (1.01 ± 0.03) times the distance
expected for the BAO peak within a concordance CDM cosmology. This first detection of the BAO peak at high redshift, when the
universe was strongly matter dominated, results in constraints on the angular diameter distance DA and the expansion rate H at z = 2.3
that, by themselves, require the existence of dark energy. Combined with constraints derived from Cosmic Microwave Background
(CMB) observations, this result implies H(z = 2.3) = (224 ± 8)kms−1Mpc−1, indicating that the time derivative of the cosmological
scale parameter ˙a = H(z = 2.3)/(1 + z) is significantly greater than that measured with BAO at z ∼ 0.5. This demonstrates that the
expansion was decelerating in the range 0.7 < z < 2.3, as expected from the matter domination during this epoch. Combined with
measurements of H0, one sees the pattern of deceleration followed by acceleration characteristic of a dark-energy dominated universe.
Kind regards and happy crunching
Martin
Independent evidence found for BAO and more in Lya-forest from
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The abstract has a lot of jargon. I beginning to dislike jargon. You start passing information past each other.
There are some who can live without wild things and some who cannot. - Aldo Leopold
The guts of this is that the
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The guts of this is that the 'Lyman alpha forest' is a pattern of radiation responses of neutral/atomic hydrogen between us and the quasars. This enables a mapping of the distribution of mass at a given redshift - which implies a certain time after the big bang - and thus how the mass/energy density has changed over time. You can compare thus what is observed vs. what is predicted for various models of cosmological evolution. In this instance the best candidate theory is lambda-CDM or Cold Dark Matter plus Dark Energy ( whoever they are ) ie. the expansion was slowing down and then it sped up again.
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
Hallo Rod! Probably this site
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Hallo Rod!
Probably this site will help you to understand better what BAO stands for. You don´t need neccessarely to unterstand all the mathematics there in. In case you need further help, let´s know. We´ll try to help you.
Kind regards and happy crunching
Martin
RE: Hallo Rod! Probably
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Thank you for clarifying Martin.
I was just being an ass:-)
Rod
There are some who can live without wild things and some who cannot. - Aldo Leopold