The ALHAMBRA survey: tight dependence of the optical mass-to-light ratio
  on galaxy colour up to z = 1.5
  Our goal is to characterise the dependence of the optical mass-to-light ratio
on galaxy colour up to z = 1.5, expanding the redshift range explored in
previous work. From the ALHAMBRA redshifts, stellar masses, and rest-frame
luminosities provided by the MUFFIT code, we derive the mass-to-light ratio vs.
colour relation (MLCR) both for quiescent and star-forming galaxies. The
intrinsic relation and its physical dispersion are derived with a Bayesian
inference model. The rest-frame i-band mass-to-light ratio of quiescent and
star-forming galaxies presents a tight correlation with the rest-frame (g - i)
colour up to z = 1.5. Such MLCR is linear for quiescent galaxies and quadratic
for star-forming galaxies. The intrinsic dispersion in these relations is 0.02
dex for quiescent galaxies and 0.06 dex for star-forming ones. The derived
MLCRs do not present a significant redshift evolution and are compatible with
previous local results in the literature. Finally, these tight relations also
hold for g- and r-band luminosities. The derived MLCRs in ALHAMBRA can be used
to predict the mass-to-light ratio from a rest-frame optical colour up to z =
1.5. These tight correlations do not change with redshift, suggesting that
galaxies have evolved along the derived relations during the last 9 Gyr.
