Systematic study of outflows in the Local Universe using CALIFA: I. Sample selection and main properties

We present a sample of 17 objects from the CALIFA survey where we find initial evidence of galactic winds based on their off-axis ionization properties. We identify the presence of outflows using various optical diagnostic diagrams [e.g. EW(H α), [N II]/H α, [S II]/H α, [O I]/H α line-ratio maps]. We find that all 17 candidate outflow galaxies lie along the sequence of active star formation in the M<SUB>⋆</SUB> versus star-formation rate (SFR) diagram, without a clear excess in the integrated SFR. The location of galaxies along the star-formation main sequence does not influence strongly the presence or not of outflows. The analysis of the SFR density (Σ<SUB>SFR</SUB>) reveals that the CALIFA sources present higher values when compared with normal star-forming galaxies. The strength of this relation depends on the calibrator used to estimate the SFR. This excess in Σ<SUB>SFR</SUB> is significant within the first effective radius supporting the idea that most outflows are driven by processes in the inner regions of a galaxy. We find that the molecular gas mass density (Σ<SUB>gas</SUB>) is a key parameter that plays an important role in the generation of outflows through its association with the local SFR. The canonical threshold reported for the generation of outflows - Σ<SUB>SFR</SUB> &gt; 0.1 M_☉ yr^{-1} kpc^{-2} - is only marginally exceeded in our sample. Within the Kennicutt-Schmidt diagram we propose a domain for galaxies hosting starburst-driven outflows defined by Σ _SFR&gt; 10^{-2} M_☉ yr^{-1} kpc^{-2} and Σ _gas&gt;10^{1.2} M_☉ pc^{-2} within a central kiloparsec region.