Single-colour diagnostics of the mass-to-light ratio-i. predictions from galaxy formation models

Abstract

Accurate galaxy stellar masses are crucial to better understand the physical mechanismsdriving the galaxy formation process. We use synthetic star formation and metal enrichmenthistories predicted by the GALFORM galaxy formation model to investigate the precisionwith which various colours (ma-mb) can alone be used as diagnostics of the stellarmass-to-light ratio. As an example, we find that, at z = 0, the intrinsic (Bf435w-Vf606w)colour can be used to determine the intrinsic rest-frame V-band stellar mass-to-light ratio(log10 ΓV = log10[(M/M⊙)/(LV /LV⊙)]) with a precision of σlgΓ≃0.06 when the initialmass function and redshift are known beforehand. While the presence of dust, assuming auniversal attenuation curve, can have a systematic effect on the inferred mass-to-light ratiousing a single-colour relation, this is typically small as it is often possible to choose a colourfor which the dust reddening vector is approximately aligned with the (ma-mb)-log10 ΓV relation. The precision with which the stellar mass-to-light ratio can be recovered using asingle-colour diagnostic rivals implementations of spectral energy distribution (SED) fittingusing more information but in which simple parametrizations of the star formation and metalenrichment histories are assumed. To facilitate the wide use of these relations, we providethe optimal observer frame colour to estimate the stellar mass-to-light ratio, along with theassociated parameters, as a function of redshift (0 < z <1.5) for two sets of commonly usedfilters. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.