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Register a new userSystematic study of outflows in the Local Universe using CALIFA: I. Sample selection and main properties
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Sebastian F. Sanchez
Publication date
2018
fields
Physics
and research's language is
English
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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$alpha$), [Nii]/H$alpha$, [Sii]/H$alpha$, [Oi]/H$alpha$ line-ratio maps). We find that all 17 candidate outflow galaxies lie along the sequence of active star formation in the M$_star$ vs. star-formation rate diagram, without a clear excess in the integrated SFR. The location of galaxies along the star-formation main sequence (SFMS) does not influence strongly the presence or not of outflows. The analysis of the star-formation rate density ($Sigma_{rm SFR}$) 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 $Sigma_{rm SFR}$ 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 ($Sigma_mathrm{gas}$) 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 -- $Sigma_{rm SFR}>0.1$ $mathrm{M}_odot mathrm{yr}^{-1} mathrm{kpc}^{-2}$ -- is only marginally exceeded in our sample. Within the Kennicutt-Schmidt diagram we propose a domain for galaxies hosting starburst-driven outflows defined by $Sigma_{rm SFR}>10^{-2} ,mathrm{M}_odot mathrm{yr}^{-1} mathrm{kpc}^{-2}$ and $Sigma_mathrm{gas}>10^{1.2} , mathrm{M}_odot mathrm{pc}^{-2}$ within a central kiloparcec region.
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The Calar Alto Legacy Integral Field Area survey (CALIFA survey) is providing Integral Field Spectroscopy (IFS) data in the entire optical window for a diameter-limited sample of 600 objects in the Local Universe (0.005$<$z$<$0.03). One of the main goals of this survey is to explore the spatial distribution of the star formation in nearby galaxies free from the limitations associated to either UV (dust attenuation) or narrow-band H$alpha$ imaging (underlying H$beta$ absorption). These are limitations that have prevented (until now) carrying out a detailed study of the evolution of the SFR by components (nuclei, bulges, disks), even locally. This kind of studies are key, for example, for understanding how galaxies really evolve from the Blue Cloud to the Red Sequence. We will first discuss in detail the validity of the assumption that the SFR given by the extincion-corrected H$alpha$ is a good measure of the total SFR by means of cross-comparing this with other SFR estimators, namely the integrated UV+22$mu$m, UV+TIR, H$alpha_{rm{obs}}$+22$mu$m, or H$alpha_{rm{obs}}$+TIR. Only once these effects are properly accounted for we can obtain preliminary results from the spatially-resolved analysis of the contribution of disks to the total SFR in the Local Universe, as a local benchmark for future studies of disks at high redshift. Our analysis shows that at least in the Local Universe the H$alpha$ luminosity derived from observations of the CALIFA IFS survey can be used to trace the SFR and that the disk to total (disk + bulge) SFR ratio is on average $sim$88 $%$.
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