The BOSS–WiggleZ overlap region – I. Baryon acoustic oscillations

Abstract

We study the large-scale clustering of galaxies in the overlap region of the Baryon Oscillation Spectroscopic Survey (BOSS) CMASS sample and the WiggleZ Dark Energy Survey. We calculate the auto-correlation and cross-correlation functions in the overlap region of the two datasets and detect a Baryon Acoustic Oscillation (BAO) signal in each of them. The BAO measurement from the cross-correlation function represents the first such detection between two different galaxy surveys. After applying density-field reconstruction we report distance-scale measurements D V r fid s /r s = (1970±45, 2132±65, 2100±200) Mpc from CMASS, the cross-correlation and WiggleZ, respectively. The distance scales derived from the two datasets are consistent, and are also robust against switching the displacement fields used for reconstruction between the two surveys. We use correlated mock realizations to calculate the covariance between the three BAO constraints. This approach can be used to construct a correlation matrix, permitting for the first time a rigorous combination of WiggleZ and CMASS BAO measurements. Using a volume-scaling technique, our result can also be used to combine WiggleZ and future CMASS DR12 results. Finally, we show that the relative velocity effect, a possible source of systematic uncertainty for the BAO technique, is consistent with zero for our samples.

The clustering of the SDSS-IV extended Baryon Oscillation Spectroscopic Survey DR14 quasar sample: first measurement of baryon acoustic oscillations between redshift 0.8 and 2.2

“…A separate systematic uncertainty is the possible shift in the acoustic peak due to a coupling of the quasar density field to the small relative velocity between baryons and cold dark matter at high redshift (Tseliakhovich & Hirata 2010;Dalal et al 2010;Yoo et al 2011;Slepian & Eisenstein 2015;Blazek et al 2016;Schmidt 2016). This has been shown to be less than 0.5 per cent for low redshift galaxies (Yoo et al 2013;Beutler et al 2016;) and we expect it to be a minor effect for quasars with z ∼ 1.5, compared to our statistical uncertainty. Further study is warranted, especially as the statistical uncertainty will be considerably improved with future datasets.…”

Constraining the relative velocity effect using the Baryon Oscillation Spectroscopic Survey

“…The idea is that one sample contains old galaxies, which formed early and retained the relative velocity effect, while the second sample contains young galaxies which will have a smaller (or no) relative velocity effect. Such an analysis was performed in Beutler et al (2015) using the BOSS and WiggleZ galaxies. The BOSS sample contains mainly old LRG galaxies, which should carry a stronger relative velocity effect, compared to the ELG galaxies observed in WiggleZ.…”

The SDSS-IV Extended Baryon Oscillation Spectroscopic Survey: Baryon Acoustic Oscillations at Redshift of 0.72 with the DR14 Luminous Red Galaxy Sample

“…Both measurements are made over the same redshift range, 0.6<z<1.0, but are nearly independent since the current overlap between eBOSS and WiggleZ is small (half of region "S1" of WiggleZ is covered by eBOSS LRGs). This overlap will be larger by the end of eBOSS observations, and a careful estimate of the correlations between the two surveys will be needed (as made with BOSS CMASS in Beutler et al 2016).…”

“…We leave more realistic calculations of this correlation using correlated mock catalogs (as in, e.g., Beutler et al 2016) for future work. Forecasts in Zhao et al (2016) predict 1% precision on isotropic BAO with 7000 deg 2 for the final eBOSS LRG sample (when combined with the high-redshift tail of CMASS).…”