Color--Mass-to-Light Ratio Relations for Disk Galaxies

Understand

We combine Spitzer $3.6\mu$ observations of a sample of disk galaxies spanning over 10 magnitudes in luminosity with optical luminosities and colors to test population synthesis prescriptions for computing stellar mass.

• Many commonly employed models fail to provide self-consistent results: the stellar mass estimated from the luminosity in one band can differ grossly from that of another band for the same galaxy.
• Independent models agree closely in the optical ($V$-band), but diverge at longer wavelengths.
• This effect is particularly pronounced in recent models with substantial contributions from TP-AGB stars.