Accurate galaxy stellar masses are crucial to better understand the physical mechanisms driving the galaxy formation process .
We use synthetic star formation and metal enrichment histories predicted by the galform galaxy formation model to investigate the precision with which various colours ( m _ { a } - m _ { b } ) can alone be used as diagnostics of the stellar mass-to-light ratio .
As an example , we find that , at z = 0 , the intrinsic ( B _ { f 435 w } - V _ { f 606 w } ) colour can be used to determine the intrinsic rest-frame V -band stellar mass-to-light ratio ( \log _ { 10 } \Gamma _ { V } = \log _ { 10 } [ ( M / M _ { \odot } ) / ( L _ { V } / L _ { V \odot } ) ] ) with a precision of \sigma _ { lg \Gamma } \simeq 0.06 when the initial mass function and redshift are known beforehand .
While the presence of dust , assuming a universal attenuation curve , can have a systematic effect on the inferred mass-to-light ratio using a single-colour relation , this is typically small as it is often possible to choose a colour for which the dust reddening vector is approximately aligned with the ( m _ { a } - m _ { b } ) - \log _ { 10 } \Gamma _ { V } relation .
The precision with which the stellar mass-to-light ratio can be recovered using a single colour diagnostic rivals implementations of SED fitting using more information but in which simple parameterisations of the star formation and metal enrichment histories are assumed .
To facilitate the wide use of these relations , we provide the optimal observer frame colour to estimate the stellar mass-to-light ratio , along with the associated parameters , as a function of redshift ( 0 < z < 1.5 ) for two sets of commonly used filters .