Differential enrichment between $alpha$- and Fe-peak elements is known to be strongly connected with the shape of the star formation history (SFH), the star formation efficiency (SFE), the inflow and outflow of material, and even the shape of the Initial Mass Function (IMF). However, beyond the Local Group detailed explorations are mostly limited to early-type galaxies due to the lack of a good proxy for [$alpha$/Fe] in late-type ones, limiting our understanding of the chemical enrichment process. We intent to extend the explorations of [$alpha$/Fe] to late-type galaxies, in order to understand the details of the differential enrichment process. We compare the gas phase oxygen abundance with the luminosity weighted stellar metallicity in an extensive catalog of $sim$25,000 H ii regions extracted from the Calar Alto Legacy Integral Field Area (CALIFA) survey, an exploration using integral field spectroscopy of $sim$900 galaxies, covering a wide range of masses and morphologies. This way we define [O/Fe] as the ratio between both parameters, proposing it as an indirect proxy of the [$alpha$/Fe] ratio. Results. We illustrate how the [O/Fe] parameter describes the chemical enrichment process in spiral galaxies, finding that: (i) it follows the decreasing pattern with [Fe/H] reported for the [$alpha$/Fe] ratio and (ii) its absolute scale depends of the stellar mass and the morphology. We reproduce both patterns using two different chemical evolution models (ChEM), considering that galaxies with different stellar mass and morphology present (i) different SFHs, SFEs and different inflow/outflow rates, or (ii) a different maximum stellar mass cut for the IMF. We will explore the differential chemical enrichment using this new proxy galaxy by galaxy and region by region in further studies.
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