Consistency checks in the ΛCDM: transparency, BAO scale and Λ-domination

Abstract

Within the ΛCDM model, we perform consistency checks among different distance measures, combining Supernovae Type Ia (SNIa) data, direct measurements of Hubble expansion H ( z ), and the Baryon acoustic oscillation (BAO) scale. We present new constraints on cosmic transparency using both H ( z ) and the latest SNIa (Union) data. For a flat model, this improves current constraints by nearly an order of magnitude. We also revisit the recently reported tension between the BAO scale and SNIa data in light of possible deviations from transparency, and conclude that the source of the discrepancy may most likely be found in systematic effects in modelling of the low redshift data, or simply in a ∼ 2- σ statistical fluke, rather than in exotic physics. Finally, combining H ( z ) and SNIa data, we attempt to draw model-independent conclusions about the recent accelerated expansion, and determine the acceleration redshift to z a c c = 0.35 − 0.13 + 0.20 (1- σ ).