On the mass-to-light ratio of the local Galactic disc and the optical luminosity of the Galaxy

• Published in: Monthly notices of the Royal Astronomical Society Vol. 372; no. 3; pp. 1149 - 1160
• Main Authors: Flynn, Chris, Holmberg, Johan, Portinari, Laura, Fuchs, Burkhard, Jahreiß, Hartmut
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-11-2006; Blackwell Science; Oxford University Press
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology; galaxies: fundamental parameters; Galaxy: disc; Luminosity; Milky Way; Stars & galaxies; galaxies: fundamental parameters; Galaxy: disc; Mass to light ratio; Color; Disk galaxies; Tully Fisher relation; Luminosity; Main sequence stars; Galactic disks; Milky Way; Solar neighborhood; Initial mass function; Cylinders; Luminosity function
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1111/j.1365-2966.2006.10911.x

We measure the volume luminosity density and surface luminosity density generated by the Galactic disc, using accurate data on the local luminosity function and the vertical structure of the disc. From the well-measured volume mass density and surface mass density, we derive local volume and surface mass-to-light ratios (M/L) for the Galactic disc, in the bands B, V and I. We obtain M/L for the local column of stellar matter of (M/L)B= 1.4 ± 0.2, (M/L)V= 1.5 ± 0.2 and (M/L)I= 1.2 ± 0.2. The dominant contributors to the surface luminosity in these bands are main-sequence turnoff stars and giants. Our results on the colours and M/L for the ‘solar cylinder’ well agree with population synthesis predictions using initial mass functions typical of the solar neighbourhood. Finally, we infer the global luminosity of the Milky Way, which appears to be underluminous by about 1σ with respect to the main locus of the Tully–Fisher relation, as observed for external galaxies.