The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: BAO measurement from the LOS-dependent power spectrum of DR12 BOSS galaxies (1509.06373v2)

Abstract: [abridged] We present an anisotropic analysis of the baryonic acoustic oscillation (BAO) scale in the twelfth and final data release of the Baryonic Oscillation Spectroscopic Survey (BOSS). We independently analyse the LOWZ and CMASS galaxy samples: the LOWZ sample contains contains 361 762 galaxies with an effective redshift of $z_{\rm LOWZ}=0.32$; the CMASS sample consists of 777 202 galaxies with an effective redshift of $z_{\rm CMASS}=0.57$. We extract the BAO peak position from the monopole power spectrum moment, $\alpha_0$, and from the $\mu^2$ moment, $\alpha_2$, where $\mu$ is the cosine of the angle to the line-of-sight. The $\mu^2$-moment provides equivalent information to that available in the quadrupole but is simpler to analyse. After applying a reconstruction algorithm to reduce the BAO suppression by bulk motions, we measure the BAO peak position in the monopole and $\mu^2$-moment, which are related to radial and angular shifts in scale. We report $H(z_{\rm LOWZ})r_s(z_d)=(11.60\pm0.60)\cdot10^3 {\rm km}s^{-1}$ and $D_A(z_{\rm LOWZ})/r_s(z_d)=6.66\pm0.16$ with a cross-correlation coefficient of $r_{HD_A}=0.41$, for the LOWZ sample; and $H(z_{\rm CMASS})r_s(z_d)=(14.56\pm0.37)\cdot10^3 {\rm km}s^{-1}$ and $D_A(z_{\rm CMASS})/r_s(z_d)=9.42\pm0.13$ with a cross-correlation coefficient of $r_{HD_A}=0.47$, for the CMASS sample. We combine these results with the measurements of the BAO peak position in the monopole and quadrupole correlation function of the same dataset \citep[][companion paper]{Cuestaetal2015} and report the consensus values: $H(z_{\rm LOWZ})r_s(z_d)=(11.63\pm0.69)\cdot10^3 {\rm km}s^{-1}$ and $D_A(z_{\rm LOWZ})/r_s(z_d)=6.67\pm0.15$ with $r_{HD_A}=0.35$ for the LOWZ sample; $H(z_{\rm CMASS})r_s(z_d)=(14.67\pm0.42)\cdot10^3 {\rm km}s^{-1}$ and $D_A(z_{\rm CMASS})/r_s(z_d)=9.47\pm0.12$ with $r_{HD_A}=0.52$ for the CMASS sample.

• The paper presents a BAO analysis using an anisotropic Fourier-space power spectrum approach to measure cosmic distance scales and the universe's expansion history.
• It independently analyzes LOWZ and CMASS galaxy samples, reporting robust measurements such as H(z_LOWZ)r_s = (11.60 ± 0.60)×10³ km/s and H(z_CMASS)r_s = (14.56 ± 0.37)×10³ km/s.
• The refined methodology minimizes redshift-space distortion complexities and cross-validates results with companion studies, tightening constraints on cosmological models.

Anisotropic BAO Analysis in the SDSS-III DR12 BOSS Findings

This paper presents a comprehensive analysis of the Baryonic Acoustic Oscillation (BAO) scale utilizing data from the twelfth data release (DR12) of the Baryon Oscillation Spectroscopic Survey (BOSS). The analysis adopts an anisotropic approach, furthering methods used in prior data releases to evaluate the line-of-sight (LOS)-dependent clustering in galaxy distributions. A key aspect of this paper is the independent evaluation of the LOWZ and CMASS galaxy samples, with LOWZ containing approximately 361,762 galaxies and CMASS approximately 777,202 galaxies, giving effective redshifts of $z_{\rm LOWZ} = 0.32$ and $z_{\rm CMASS} = 0.57$, respectively.

By employing Fourier-space power spectrum analysis, the paper focuses on extracting the BAO peak position from the monopole moment ($\alpha_0$) and the $\mu^2$ moment ($\alpha_2$), which provides analogous details to the quadrupole but simplifies the analysis framework by minimizing RSD complexities. This methodology involves the application of a reconstruction algorithm aimed at canceling BAO suppression due to bulk motions, gauging radial and angular shifts robustly.

The results illustrate distinct parameters obtained from both the LOWZ and CMASS samples. Specifically, for the LOWZ sample, the paper determines:

• $$H(z_{\rm LOWZ})r_s(z_d) = (11.60 \pm 0.60) \cdot 10^3 \, \text{km s}^{-1}$$
• $D_A(z_{\rm LOWZ})/r_s(z_d) = 6.66 \pm 0.16$ with a correlation coefficient $r_{HD_A} = 0.41$.

For the CMASS sample, the outcomes are:

• $$H(z_{\rm CMASS})r_s(z_d) = (14.56 \pm 0.37) \cdot 10^3 \, \text{km s}^{-1}$$
• $D_A(z_{\rm CMASS})/r_s(z_d) = 9.42 \pm 0.13$ with a correlation coefficient $r_{HD_A} = 0.47$.

The paper highlights that the results remain unaffected by the fiducial cosmology assumed, demonstrating robustness against systematic biases. Moreover, when aligned with parallel findings from the correlation function analysis (detailed in a companion paper by Cuesta et al.), consensus values are derived, confirming:

• For LOWZ: $$H(z_{\rm LOWZ})r_s(z_d) = (11.63 \pm 0.69) \cdot 10^3 \, \text{km s}^{-1}$$ and $D_A(z_{\rm LOWZ})/r_s(z_d) = 6.67 \pm 0.15$
• For CMASS: $$H(z_{\rm CMASS})r_s(z_d) = (14.67 \pm 0.42) \cdot 10^3 \, \text{km s}^{-1}$$ and $D_A(z_{\rm CMASS})/r_s(z_d) = 9.47 \pm 0.12$.

These findings are significant as they contribute to an accurate estimation of cosmological distances, offering essential insight into the expansion history of the universe. The refined methodologies employed, particularly the $\mu^2$-moment simplification, signify an essential step forward in reducing computational complexity while maintaining precise BAO measurements.

Strategically, the results from this analysis provide tighter constraints on cosmological models and enhance our capability to decipher fundamental cosmological parameters, forming a robust data-driven foundation for ongoing and future explorations in cosmic structure and evolution. Further, this approach's coherence with related methodological outputs sets the stage for continued refinement and application across broader cosmological contexts.