Cosmological constraints from galaxy multi-tracers in the nearby
  Universe
  The Baryon Acoustic Oscillation (BAO) scale in the clustering of galaxies is
a powerful standard ruler to measure cosmological distances and determine the
geometry of the Universe. Past surveys have detected the BAO feature in the
clustering of different galaxy samples, most of them composed of redder,
quiescent galaxies and bluer, star-forming ones out to redshift $z\sim1$.
Besides these targets, new upcoming surveys will observe high-redshift galaxies
with bright nebular emission lines out to $z\sim2$, quasars and Lyman-$\alpha$
quasars at $z\gt 2$. All these different galaxy targets will be used as
multi-tracers of the same underlying dark matter field. By combining them over
wide cosmological volumes, we will be able to beat cosmic variance and measure
the growth of structure with unprecedented accuracy. In this work, we measure
the BAO scale in the two-point auto- and cross-correlation functions of three
independent populations of multi-tracers extracted from the SDSS DR7 Main
galaxy sample at redshift $0.02\lt z\lt 0.22$. Combining their covariances, we
find accurate constraints on the shift parameter $\alpha=1.00\pm 0.04$ and
$D_{\rm{V}}(z=0.1)/r_{\rm{s}}=2.92\pm0.12$.
