1207.6216 (F. F. Rosales-Ortega et al.)

A new scaling relation for HII regions in spiral galaxies: unveiling the true nature of the mass-metallicity relation    [PDF]

F. F. Rosales-Ortega, S. F. Sánchez, J. Iglesias-Páramo, A. I. Díaz, J. M. Vílchez, J. Bland-Hawthorn, B. Husemann, D. Mast

We demonstrate the existence of a -local- relation between galaxy surface mass density, gas metallicity, and star-formation rate density using spatially-resolved optical spectroscopy of HII regions in the local Universe. One of the projections of this distribution, -the local mass-metallicity relation- extends over three orders of magnitude in galaxy mass density and a factor of eight in gas metallicity. We explain the new relation as the combined effect of the differential radial distributions of mass and metallicity in the discs of galaxies, and a selective star-formation efficiency. We use this local relation to reproduce -with remarkable agreement- the total mass-metallicity relation seen in galaxies, and conclude that the latter is a scale-up integrated effect of a local relation, supporting the inside-out growth and downsizing scenarios of galaxy evolution.

View original: http://arxiv.org/abs/1207.6216