Analysis of the Internal Radial Gradient of Chemical Abundances in Spiral Galaxies from CALIFA

TL;DR

This paper investigates the inner radial gradients of oxygen abundance in spiral galaxies using CALIFA survey data, revealing how different analysis criteria and diffuse ionized gas influence observed abundance profiles.

Contribution

It introduces an automated method to analyze oxygen abundance gradients and examines the effects of ionization source classification and DIG decontamination on gradient profiles.

Findings

Different criteria for ionization source classification significantly affect gradient results.

Diffuse ionized gas impacts oxygen abundance measurements, especially in galaxy centers.

Inner drops in abundance gradients are linked to galaxy properties and analysis methods.

Abstract

The study of chemical evolution is of paramount importance for understanding the galaxies evolution. Models and observations propose an inside-out mechanism in the formation of spiral galaxy disks implying a negative radial gradient of elemental abundances when represented in logarithmic scale. However, observed chemical abundance gradients, in some instances, deviate from a single linear negative straight line, revealing inner drops or outer flattenings, particularly in more massive galaxies. This study analyzes oxygen abundance gradients in spiral galaxies based on observations from the Calar Alto Legacy Integral Field Area (CALIFA) survey. Our focus is specifically on examining oxygen abundance gradient profiles, as obtained with data from HII regions, with a special emphasis on the inner radial gradient. We employ an automated fitting procedure to establish correlations between the physical properties of galaxies and bulges and the presence of these inner drops, seeking for potential explanations for these gradient variations. We find that the different criteria used in the literature to distinguish HII regions from other ionization sources in the galaxy, such as Active Galactic Nuclei, significantly impact the results, potentially altering abundance gradient profiles and uncovering galaxies with distinct inner drops. Additionally, we analyze the abundance radial gradients to investigate the impact of diffuse ionized gas (DIG) decontamination on oxygen abundances over the featuring inner drops. We observe that DIG, concentrated mainly in the central regions of galaxies, can modify oxygen abundance gradient profiles if left unaddressed.