Angular Baryon Acoustic Oscillation measure at z=2.225 from the SDSS quasar survey

TL;DR

This paper measures the angular BAO scale at redshift 2.225 using quasar data from SDSS DR12Q, providing a quasi model-independent high-redshift cosmological probe with results consistent with LCDM.

Contribution

It presents the first high-redshift angular BAO measurement using quasars with a quasi model-independent approach and assesses its robustness and cosmological implications.

Findings

Measured angular BAO scale: 1.77 +- 0.31 degrees at z=2.225

BAO detection significance: 2.12 sigma (97% confidence)

Constraints on cosmological parameters align with LCDM model.

Abstract

Following a quasi model-independent approach we measure the transversal BAO mode at high redshift using the two-point angular correlation function (2PACF). The analyses done here are only possible now with the quasar catalogue from the twelfth data release (DR12Q) from the Sloan Digital Sky Survey, because it is spatially dense enough to allow the measurement of the angular BAO signature with moderate statistical significance and acceptable precision. Our analyses with quasars in the redshift interval z = [2.20,2.25] produce the angular BAO scale theta_BAO = 1.77 +- 0.31 deg with a statistical significance of 2.12 sigma (i.e., 97% confidence level), calculated through a likelihood analysis performed using the theoretical covariance matrix sourced by the analytical power spectra expected in the LCDM concordance model. Additionally, we show that the BAO signal is robust -although with less statistical significance- under diverse bin-size choices and under small displacements of the quasars' angular coordinates. Finally, we also performed cosmological parameter analyses comparing the theta_BAO predictions for wCDM and w(a)CDM models with angular BAO data available in the literature, including the measurement obtained here, jointly with CMB data. The constraints on the parameters Omega_M, w_0 and w_a are in excellent agreement with the LCDM concordance model.