  In the theory of structure formation, galaxies are biased tracers of the
underlying matter density field. The statistical relation between galaxy and
matter density field is commonly referred as galaxy bias. In this paper, we
test the linear bias model with weak-lensing and galaxy clustering measurements
in the 2 square degrees COSMOS field (Scoville et al. 2007). We estimate the
bias of galaxies between redshifts z=0.2 and z=1, and over correlation scales
between R=0.2 h^-1 Mpc and R=15 h^-1 Mpc. We focus on three galaxy samples,
selected in flux (simultaneous cuts I_814W < 26.5 and K_s < 24), and in
stellar-mass (10^9 < M_* < 10^10 h^-2 Msun and 10^10 < M^*< 10^11 h^-2 Msun).
At scales R > 2 h^-1 Mpc, our measurements support a model of bias increasing
with redshift. The Tinker et al. (2010) fitting function provides a good fit to
the data. We find the best fit mass of the galaxy halos to be log(M_200 h^-1
Msun) = 11.7^+0.6_-1.3 and log(M_200 h^-1 Msun) = 12.4^+0.2_-2.9 respectively
for the low and high stellar-mass samples. In the halo model framework, bias is
scale-dependent with a change of slope at the transition scale between the one
and the two halo terms. We detect a scale-dependence of bias with a turn-down
at scale R=2.3\pm1.5 h^-1 Mpc, in agreement with previous galaxy clustering
studies. We find no significant amount of stochasticity, suggesting that a
linear bias model is sufficient to describe our data. We use N-body simulations
to quantify both the amount of cosmic variance and systematic errors in the
measurement.
