MEGADES: MEGARA galaxy disc evolution survey Ionised gas diagnosis
We present the ionised gas properties and metallicity gradients of the central area of a sample of 43 galaxies using observations obtained by the MEGADES survey. The technical capabilities of MEGARA (Multi-Espectrógrafo en GTC de Alta Resolución para Astronomía) provide us with relatively high spect...
| Autores: | , , , , , , , , , , , , , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2026 |
| País: | España |
| Institución: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositorio: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:dnet:digitalcsic_::d7e26019c895d85bff3ebc265239db32 |
| Acceso en línea: | http://hdl.handle.net/10261/427697 |
| Access Level: | acceso abierto |
| Palabra clave: | Galaxies: ISM Galaxies: star formation |
| Sumario: | We present the ionised gas properties and metallicity gradients of the central area of a sample of 43 galaxies using observations obtained by the MEGADES survey. The technical capabilities of MEGARA (Multi-Espectrógrafo en GTC de Alta Resolución para Astronomía) provide us with relatively high spectral (R ∼ 6000) and spatial (0.62″) resolution observations that we used to study the properties of the ionised gas via various methods, including using the classic diagnostic BPT diagrams of its [N II] and [S II] variants. We explore how the diagrams vary as a function of both the radius and velocity dispersion of the Hα line. We also propose a new diagnostic diagram for assessing the relative contributions of active galactic nuclei (AGN), shocks, and H II regions in each spatial region as the ratio between the velocity dispersion of the [N II]λ6584 and Hα lines. A considerable number of regions, regardless of their galactocentric distance, have emission line spectra associated with shocks. This inference follows both from their line ratios, typically characterised by high [N II]λ6584/Hα and intermediate [O III]λ5007/Hβ, and from their position in our diagnostic diagram, where they lie between the areas associated with HII regions and with AGN. The better selection of HII-region-like emission allowed for a robust oxygen abundance determination using the N2 indicator, which we used to measure precise abundance gradients. Most galaxies show negligible metallicity gradients, especially the low-abundance (< 8.37 dex) fast rotators. The mean value of the slope of the metallicity gradients for this subset is 0.005 dex Re−1, with a dispersion of 0.422 dex Re−1. Above 8.37 dex the fast rotators consistently show slightly negative metallicity gradients, with a weak correlation between the slope and the y-intercept. The mean slope of these galaxies is −0.681 dex Re−1, with a dispersion of 0.933 dex Re−1. The overall mean value of the gradients for all galaxies in the MEGADES sample is −0.025 dex Re−1, with a dispersion of 0.766 dex Re−1. We discuss the possible implications of these results regarding the impact of galactic winds on the abundance gradients of galaxies. © The Authors 2026. |
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