Vol. 552
In section 3. Cosmology

Baryon acoustic oscillations in the Lyman alpha forest of BOSS quasars

by N. G. Busca, T. Delubac, J. Rich, et al. A&A 552, A96


Baryonic acoustic oscillations (BAO) are density fluctuations of the cosmic baryonic matter component caused by acoustic waves that existed in the early Universe. The signatures of such fluctuations imprinted in the anisotropies of the cosmic microwave background (CMB) were observed more than a decade ago; more recently, BAOs have also been detected at redshift z = 0.3 as a peak in the galaxy-galaxy correlation function. The authors of this paper present the first detection of the BAO peak at z=2.3 obtained using the filamentary structure of the relic intergalactic neutral hydrogen density, often referred to as the Lyman Alpha Forest. Using this technique, coupled with previous theoretical results, they have been able to obtain constraints on the angular diameter distance and the cosmic expansion rate, thereby confirming the deceleration of the Universe in the redshift range 0.7 < z < 2.3. This picture is consistent with the concordance Lambda CDM model that includes a dark energy component.