Full-shape cosmology analysis of SDSS-III BOSS galaxy power spectrum using emulator-based halo model: a $5%$ determination of $σ_8$

Kavli Affiliate: Masahiro Takada

| First 5 Authors: Yosuke Kobayashi, Takahiro Nishimichi, Masahiro Takada, Hironao Miyatake,

| Summary:

We present the results obtained from the full-shape cosmology analysis of the
redshift-space power spectra for 4 galaxy samples of the SDSS-III BOSS DR12
galaxy catalog over $0.2 < z < 0.75$. For the theoretical template, we use an
emulator that was built from an ensemble set of $N$-body simulations, which
enables fast and accurate computation of the redshift-space power spectrum of
halos. Combining with the halo occupation distribution to model the halo-galaxy
connection, we can compute the redshift-space power spectrum of BOSS-like
galaxies in the flat $Lambda$CDM cosmology. In our cosmology inference, we use
the power spectrum monopole, quadrupole and hexadecapole and include 7 nuisance
parameters to model uncertainties in the halo-galaxy connection for each galaxy
sample, but do not use any information on the abundance of galaxies. We
demonstrate a validation of our analysis pipeline using the mock catalogs of
BOSS-like galaxies, generated using different recipes of the halo-galaxy
connection and including the assembly bias effect. Assuming weak priors on
cosmological parameters, except for $Omega_{rm b}h^2$ and $n_{rm s}$, we
show that our model well reproduces the BOSS power spectra. Including the power
spectrum information up to $k_{rm max}=0.25,h{rm Mpc}^{-1}$, we find
$Omega_{rm m}=0.300pm0.011$, $H_0=68.35^{+1.21}_{-1.39}{rm km,s}^{-1}{rm
Mpc}^{-1}$, and $sigma_8=0.742^{+0.035}_{-0.036}$, for the mode and 68%
credible interval, after marginalization over nuisance parameters. We find
little improvement in the cosmological parameters beyond a maximum wavelength
$k_{rm max}simeq 0.2,h,{rm Mpc}^{-1}$ due to the shot noise domination and
marginalization of the halo-galaxy connection parameters. Our results show a
nice agreement with the {it Planck} CMB results for $Omega_{rm m}$ and
$H_0$, but indicate a slight tension for $sigma_8$.

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