Spatially Resolved Star Formation Main Sequence of Galaxies in the Califa Survey

Cano-Díaz, M. et. al.The >main sequence of galaxies> - defined in terms of the total star formation rate ψ versus the total stellar mass M - is a well-studied tight relation that has been observed at several wavelengths and at different redshifts. All earlier studies have derived this relation from integrated properties of galaxies. We recover the same relation from an analysis of spatially resolved properties, with integral field spectroscopic (IFS) observations of 306 galaxies from the CALIFA survey. We consider the SFR surface density in units of log(M yr Kpc) and the stellar mass surface density in units of log(M Kpc) in individual spaxels that probe spatial scales of 0.5-1.5 Kpc. This local relation exhibits a high degree of correlation with small scatter (σ = 0.23 dex), irrespective of the dominant ionization source of the host galaxy or its integrated stellar mass. We highlight (i) the integrated star formation main sequence formed by galaxies whose dominant ionization process is related to star formation, for which we find a slope of 0.81 ± 0.02; (ii) for the spatially resolved relation obtained with the spaxel analysis, we find a slope of 0.72 ± 0.04; and (iii) for the integrated main sequence, we also identified a sequence formed by galaxies that are dominated by an old stellar population, which we have called the retired galaxies sequence.Financial support: M.C.D. and S.F.S.: DGAPA-UNAM funding; CONACyT-180125 and PAPIIT IA-100815 projects. Z.S.: EU Marie Curie Career Integration Grant >SteMaGE> PCIG12-GA-2012-326466. Y.A.: RyC-2011-09461 and AYA2013-47742-C4-3-P projects from the Spanish MINECO and the SELGIFS programme, funded by the EU (FP7-PEOPLE-2013-IRSES-612701). C.J.W.: Marie Curie Career Integration Grant 303912. R.M.G.D.: AyA2014-57490-P and J.A. P12-FQM2828 grants. J.F.B.: AYA2013-48226-C3-1-P from the Spanish MINECO grant. L.G.: Millennium Science Initiative through grant IC120009, and by CONICYT through FONDECYT grant 3140566.Peer Reviewe