Open AccessOn the mass‐to‐light ratio and the initial mass function in disc galaxies
Author(s) -
Portinari L.,
SommerLarsen J.,
Tantalo R.
Publication year - 2004
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2004.07207.x
Subject(s) - physics , astrophysics , mass to light ratio , bulge , initial mass function , spiral galaxy , galaxy , stars , stellar mass , mass ratio , tully–fisher relation , astronomy , galaxy formation and evolution , star formation , galaxy rotation curve , luminosity function , redshift
A low mass‐to‐light ( M / L ) ratio for the stellar component of spiral galaxies ( M / L ≲ 1 in the I band) is advocated by various dynamical arguments and by recent cosmological simulations of the formation of these systems. We discuss this possibility by means of chemo‐photometric models for galactic discs, adopting different initial mass functions (IMFs). We show that a number of ‘bottom‐light’ initial mass functions (namely, with less mass locked in low‐mass stars than the standard Salpeter IMF), suggested independently in recent literature, do imply M / L ratios as low as mentioned above, at least for late‐type spirals (Sbc/Sc). This conclusion still holds when the bulge contribution to mass and light is included. We also predict the typical stellar M / L ratio, and correspondingly the zero‐point of the Tully–Fisher relation, to vary considerably with Hubble type (approximately 0.5–0.7 mag in the red bands, from Sa to Sc type). For some of the bottom‐light IMFs considered, the efficiency of metal production tends to exceed what is typically estimated for spiral galaxies. Suitable tuning of the IMF mass limits, post‐supernova fallback of metals on to black holes or metal outflows must then be invoked, to reproduce the observed chemical properties of disc galaxies. In the appendix we provide M / L –colour relations to estimate the stellar M / L ratio of a galaxy on the basis of its colours, for several IMFs.