Stellar Mass-to-light Ratios: Composite Bulge+Disk Models and the
  Baryonic Tully-Fisher Relation
  We present stellar population models to calculate the mass-to-light ratio
($\Upsilon_*$) based on galaxy's colors ranging from $GALEX$ FUV to Spitzer
IRAC1 at 3.6$\mu$m. We present a new composite bulge+disk $\Upsilon_*$ model
that considers the varying contribution from bulges and disks based on their
optical and near-IR colors. Using these colors, we build plausible star
formation histories and chemical enrichment scenarios based on the star
formation rate-stellar mass and mass-metallicity correlations for star-forming
galaxies. The most accurate prescription is to use the actual colors for the
bulge and disk components to constrain $\Upsilon_*$; however, a reasonable
bulge+disk model plus total color only introduces 5% more uncertainty. Full
bulge+disk $\Upsilon_*$ prescriptions applied to the baryonic TF relation
improves the linearity of the correlation, increases the slope and reduces the
total scatter by 4%.
