Abstract
ABSTRACT 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−1 Kpc−2) and the stellar mass surface density in units of log(M ⊙ Kpc−2) 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.
Highlights
Thanks to the increasing number of statistical studies of both local and distant galaxies, it has been possible to reveal and confirm several correlations in extragalactic astronomy
We present the results of studying the spatially resolved star formation main sequence (SFMS) based on data from the Calar Alto Legacy Integral Field Area survey (CALIFA) survey
We explored the possible effects in the local SFMS determination, relaxing our criteria to select the SF regions by allowing the regions laying below the Kewley demarcation limit (KL) and whose equivalent width (EW)(Hα) are
Summary
Thanks to the increasing number of statistical studies of both local and distant galaxies, it has been possible to reveal and confirm several correlations in extragalactic astronomy. One of these relations is the so-called star formation main sequence (SFMS) of actively star-forming galaxies, which relates the star formation rate (SFR, ψ) and the stellar mass (M*). The SFMS is recovered in cosmological simulations (Davé et al 2011; Torrey et al 2014; Sparre et al 2015, hereafter S15) This correlation has been proven to be tight, with a scatter of ∼0.2–0.35 dex in observations and in theoretical predictions (D07; S15; S14). RP15 has proposed a new objective definition for the SFMS for local galaxies, which favors values of 0.76 dex and −7.64 log(Me yr−1) for the slope and zero points, respectively
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