The EDGE-CALIFA survey: self-regulation of star formation at kpc scales

Abstract

The processes that regulate star formation in the local Universe at kpc scales are essential to understand how galaxies evolve. We present the relation between the star formation rate density, ΣSFR , and the hydrostatic midplane pressure, Ph , for 4260 star-forming regions of kpc size located in 96 galaxies included in the EDGE-CALIFA survey covering a wide range of stellar masses and morphologies. We find that these two parameters are tightly correlated, exhibiting smaller scatter and strong correlation in comparison to other star-forming scaling relations. A power-law, with a slightly sub-linear index, is a good representation of this relation. Locally, the residuals of this correlation show a significant anti-correlation with both the stellar age and metallicity whereas the total stellar mass may also play a secondary role in shaping the ΣSFR Ph relation. For our sample of active star-forming regions (i.e., regions with large values of Hα equivalent width), we find that the effective feedback momentum per unit stellar mass (p∗/m∗), measured from the Ph/ΣSFR ratio increases with Ph. The median value of this ratio for all the sampled regions is larger than the expected momentum just from supernovae explosions. Morphology of the galaxies, including bars, does not seem to have a significant impact in the ΣSFR Ph relation. Our analysis suggests that self regulation of the ΣSFR at kpc scales comes mainly from momentum injection to the interstellar medium from supernovae explosions. However, other mechanism in disk galaxies may also play a significant role in shaping the ΣSFR at local scales. Our results also suggest that Ph can be considered as the main parameter that modulates star formation at kpc scales, rather than individual components of the baryonic mass.