Evolution and star formation quenching of nearby galaxies
The evolution of galaxies is largely driven not only by how stars form, but also by the way in which star formation ends. The “star formation quenching'', that accompanies the transformation of a blue spiral into a red elliptical galaxy, can be caused by a variety of phenomena connected to removal, reduction, or stabilisation of the star formation raw fuel: the cold gas.
In the context of the CALIFA survey (which observed a sample of ~1000 galaxies with an optical IFU), we are involved in a series of large observational programs to study the properties and the distribution of the molecular and atomic gases within galaxies at different phases of their evolution. These programs involve several telescopes such as APEX, CARMA, NOEMA, ACA, GBT (the EDGE project), and Effelsberg, VLA, GMRT (the MasQue project) and will provide an unprecedented dataset to unveil the evolution of galaxies in the nearby Universe.
Using this data, we have shown that galaxies quench their star formation following specific patterns, but AGNs (which are considered to be one of the main star formation quenching agents) do not seem to significantly alter the galaxy's global properties. Nevertheless, regions surrounding the AGNs appear to have lower contents of molecular and atomic gas compared to the rest of the disc. On a global scale, we have demonstrated that the retirement of galaxies is mostly regulated by how they convert the gas into stars (the so-called star formation efficiency) rather than by the absence of gas. Galactic large-scale dynamics (such as circular speed and shear) and secular evolution (driven by spiral arm, bar, and bulge interactions) appear to have a big role to modify the star formation efficiency in different regions of the galaxies.
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