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P-MaNGA Galaxies: emission-lines properties – gas ionization and chemical abundances from prototype observations
Journal article   Open access   Peer reviewed

P-MaNGA Galaxies: emission-lines properties – gas ionization and chemical abundances from prototype observations

F Belfiore, R Maiolino, K Bundy, D Thomas, C Maraston, D Wilkinson, S. F Sánchez, M Bershady, G. A Blanc, M Bothwell, …
Monthly notices of the Royal Astronomical Society, Vol.449(1), pp.867-900
02/23/2015
DOI: 10.1093/mnras/stv296
url
https://doi.org/10.1093/mnras/stv296View
Published (Version of record) Open Access

Abstract

MaNGA (Mapping Nearby Galaxies at Apache Point Observatory) is a 6-yr Sloan Digital Sky Survey (SDSS-IV) survey that will obtain spatially resolved spectroscopy from 3600 to 10 300 Å for a representative sample of over 10 000 nearby galaxies. In this paper, we present the analysis of nebular emission-line properties using observations of 14 galaxies obtained with P-MaNGA, a prototype of the MaNGA instrument. By using spatially resolved diagnostic diagrams, we find extended star formation in galaxies that are centrally dominated by Seyfert/LINER-like emission, which illustrates that galaxy characterizations based on single fibre spectra are necessarily incomplete. We observe extended low ionization nuclear emission-line regions (LINER)-like emission (up to 1Re) in the central regions of three galaxies. We make use of the Hα equivalent width [EW(Hα)] to argue that the observed emission is consistent with ionization from hot evolved stars. We derive stellar population indices and demonstrate a clear correlation between Dn(4000) and EW(HδA) and the position in the ionization diagnostic diagram: resolved galactic regions which are ionized by a Seyfert/LINER-like radiation field are also devoid of recent star formation and host older and/or more metal-rich stellar populations. We also detect extraplanar LINER-like emission in two highly inclined galaxies, and identify it with diffuse ionized gas. We investigate spatially resolved metallicities and find a positive correlation between metallicity and star formation rate surface density. We further study the relation between N/O versus O/H on resolved scales. We find that, at given N/O, regions within individual galaxies are spread towards lower metallicities, deviating from the sequence defined by galactic central regions as traced by Sloan 3-arcsec fibre spectra. We suggest that the observed dispersion can be a tracer for gas flows in galaxies: infalls of pristine gas and/or the effect of a galactic fountain.
galaxies: fundamental parameters galaxies: abundances galaxies: active galaxies: evolution galaxies: ISM

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