[alpha/Fe] traced by H II regions from the CALIFA survey. The connection between morphology and chemical abundance patterns

Abstract

Context. 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. Aims. We intent to extend the explorations of [alpha/Fe] to late-type galaxies in order to understand the details of the differential enrichment process. Methods. We compare the gas-phase oxygen abundance with the luminosity-weighted stellar metallicity in an extensive catalogue of similar to 25 000 H II regions extracted from the Calar Alto Legacy Integral Field Area (CALIFA) survey, an exploration that uses the integral-field spectroscopy of similar to 900 galaxies and covers 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. This procedure is completely different from the one adopted to estimate [alpha/Fe] from high-resolution spectroscopic data for stars in our Galaxy. 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 on the stellar mass and the morphology. We reproduce both patterns using two different chemical evolution models, considering that galaxies with different stellar masses and morphologies present either different SFHs, SFEs, and inflow and outflow rates or 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.