Mass-to-light ratio
= Mass-to-light ratio
{title2=$\Upsilon=M/L$}
The <mass-to-light ratio> compares the mass assigned to an astronomical system with its luminosity in a specified band, often in solar units. A stellar value uses only stellar mass and depends on the stellar population, age, composition and band. A dynamical value can include gas and <dark matter>, so it need not equal the stellar value. In a halo-to-galaxy mapping, $L=M_*/\Upsilon_*$ requires the stellar ratio and not the total <dark-matter halo> ratio.