We combine Spitzer $3.6\mu$ observations of a sample of disk galaxiesspanning over 10 magnitudes in luminosity with optical luminosities and colorsto test population synthesis prescriptions for computing stellar mass. Manycommonly employed models fail to provide self-consistent results: the stellarmass estimated from the luminosity in one band can differ grossly from that ofanother band for the same galaxy. Independent models agree closely in theoptical ($V$-band), but diverge at longer wavelengths. This effect isparticularly pronounced in recent models with substantial contributions fromTP-AGB stars. We provide revised color--mass-to-light ratio relations thatyield self-consistent stellar masses when applied to real galaxies. The $B-V$color is a good indicator of the mass-to-light ratio. Some additionalinformation is provided by $V-I$, but neither it nor $J-K_s$ are particularlyuseful for constraining the mass-to-light ratio on their own. In thenear-infrared, the mass-to-light ratio depends weakly on color, with typicalvalues of $0.6\; \mathrm{M}_{\odot}/\mathrm{L}_{\odot}$ in the $K_s$-band and$0.47\; \mathrm{M}_{\odot}/\mathrm{L}_{\odot}$ at $3.6\mu$.
展开▼
