Acoustic scale from the angular power spectra of SDSS-III DR8 photometric luminous galaxies

TL;DR

<p>We develop a robust template-based method to extract the acoustic scale from the angular power spectra of SDSS-III DR8 photometric luminous galaxies, leveraging a large spectroscopic training set to recover precise redshift distributions. By projecting a 3D power spectrum into the angular domain and fitting with a controlled set of nuisance terms, we measure the angular diameter distance to the sound horizon, D_A/r_s, at z≈0.54 with D_A/r_s=9.212^{+0.416}_{-0.404} and D_A=1411±65 Mpc, largely independent of the underlying cosmology. The results are validated using N-body and Gaussian mocks, tested against template variations, and combined with WMAP7 and other BAO data to constrain cosmological parameters, finding a mild tension with LCDM at z>0.35. The approach demonstrates a robust pathway for photometric BAO analyses in current and future imaging surveys, emphasizing accurate redshift-distribution calibration and controlled marginalization of non-BAO information. </p>

Abstract

We measure the acoustic scale from the angular power spectra of the Sloan Digital Sky Survey III (SDSS-III) Data Release 8 imaging catalog that includes 872,921 galaxies over ~ 10,000 deg^2 between 0.45<z<0.65. The extensive spectroscopic training set of the Baryon Oscillation Spectroscopic Survey (BOSS) luminous galaxies allows precise estimates of the true redshift distributions of galaxies in our imaging catalog. Utilizing the redshift distribution information, we build templates and fit to the power spectra of the data, which are measured in our companion paper, Ho et al. 2011, to derive the location of Baryon acoustic oscillations (BAO) while marginalizing over many free parameters to exclude nearly all of the non-BAO signal. We derive the ratio of the angular diameter distance to the sound horizon scale D_A/r_s= 9.212 + 0.416 -0.404 at z=0.54, and therefore, D_A= 1411+- 65 Mpc at z=0.54; the result is fairly independent of assumptions on the underlying cosmology. Our measurement of angular diameter distance D_A is 1.4 σhigher than what is expected for the concordance LCDM (Komatsu et al. 2011), in accordance to the trend of other spectroscopic BAO measurements for z >~ 0.35. We report constraints on cosmological parameters from our measurement in combination with the WMAP7 data and the previous spectroscopic BAO measurements of SDSS (Percival et al. 2010) and WiggleZ (Blake et al. 2011). We refer to our companion papers (Ho et al. 2011; de Putter et al. 2011) for investigations on information of the full power spectrum.

Figures (14)

• Figure 1: The true redshift distribution estimated for our photometric redshift galaxies for the four redshift bins: CMASS1 for $0.45<z_{\rm ph}<0.5$, CMASS2 for $0.5<z_{\rm ph}<0.55$, CMASS3 for $0.55<z_{\rm ph}<0.6$, and CMASS4 for $0.6<z_{\rm ph}<0.65$. The median and the mean of the combined galaxy distribution is 0.541 and 0.544, respectively.
• Figure 2: The measured angular power spectra for the four redshift bins. The solid lines show the best fits derived in § \ref{['sec:results']}. The dashed line is the template for CMASS2 which is rescaled for clarity, with redshift distortions assuming a galaxy bias of 2. The dotted line is the template without redshift distortions.
• Figure 3: Window function of CMASS2, as an example.
• Figure 4: The red circles with error bars show a power spectrum averaged over 20 N-body mocks for the same line of sight. The black points show the power spectrum of CMASS2. The dotted lines in the top panel show the shot noise contribution in both cases. The solid line in the bottom panel show the expected BAO feature.
• Figure 5: The data points show the best fit $\alpha-1$ for the N-body photoz-mocks for different lines of sight. For each line of sight, the power spectrum is averaged over 20 N-body photoz-mocks. Note that the different lines of sight are correlated.