The size of the horizon at the matter-radiation equality is a key scale of the Big Bang cosmology that is directly related to the energy-matter content of the Universe. In this letter, we argue that this scale can be accurately measured from the obse
rved clustering of galaxies in new large scale surveys. We demonstrate that the zero-crossing, r_c, of the 2-point galaxy correlation function is closely related to the horizon size at matter-radiation equality for a large variety of flat LCDM models. Using large-volume cosmological simulations, we also show that the pristine zero-crossing is unaltered by non-linear evolution of density fluctuations, redshift distortions and galaxy biases. This makes r_c a very powerful standard ruler that can be accurately measured, at a percent level, in upcoming experiments that will collect redshifts of millions of galaxies and quasars.
SIDE (Super Ifu Deployable Experiment) will be a second-generation, common-user instrument for the Grantecan (GTC) on La Palma (Canary Islands, Spain). It is being proposed as a spectrograph of low and intermediate resolution, highly efficient in mul
ti-object spectroscopy and 3D spectroscopy. SIDE features the unique possibility of performing simultaneous visible and NIR observations for selected ranges. The SIDE project is leaded by the Instituto de Astrofisica de Andalucia (IAA-CSIC) in Granada (Spain) and the SIDE Consortium is formed by a total of 10 institutions from Spain, Mexico and USA. The SIDE Feasibility Study has been completed and currently the project is under revision by the GTC Project Office.
