Measuring the baryon fraction using galaxy clustering
arxiv(2024)
摘要
The amplitude of the baryon signature in galaxy clustering depends on the
cosmological baryon fraction. We consider two ways to isolate this signal in
galaxy redshift surveys. First, we extend standard template-based Baryon
Acoustic Oscillation (BAO) models to include the amplitude of the baryonic
signature by splitting the transfer function into baryon and cold dark matter
components with freely varying proportions. Second, we include the amplitude of
the split as an extra parameter in Effective Field Theory (EFT) models of the
full galaxy clustering signal. We find similar results from both approaches.
For the Baryon Oscillation Spectroscopic Survey (BOSS) data we find
f_b≡Ω_b/Ω_m=0.173±0.027 for template fits
post-reconstruction, f_b=0.153±0.029 for template fits pre-reconstruction,
and f_b=0.154±0.022 for EFT fits, with an estimated systematic error of
0.013 for all three methods. Using reconstruction only produces a marginal
improvement for these measurements. Although significantly weaker than
constraints on f_b from the Cosmic Microwave Background, these measurements
rely on very simple physics and, in particular, are independent of the sound
horizon. In a companion paper we show how they can be used, together with Big
Bang Nucleosynthesis measurements of the physical baryon density and
geometrical measurements of the matter density from the Alcock-Paczynski
effect, to constrain the Hubble parameter. While the constraints on H_0 based
on density measurements from BOSS are relatively weak, measurements from DESI
and Euclid will lead to errors on H_0 that are competitive with those from
local distance ladder measurements.
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