BELFIORE, FRANCESCO MICHEL CONCETTOFRANCESCO MICHEL CONCETTOBELFIOREMaiolino, RobertoRobertoMaiolinoMaraston, ClaudiaClaudiaMarastonEmsellem, EricEricEmsellemBershady, Matthew A.Matthew A.BershadyMasters, Karen L.Karen L.MastersYan, RenbinRenbinYanBizyaev, DmitryDmitryBizyaevBoquien, MédéricMédéricBoquienBrownstein, Joel R.Joel R.BrownsteinBundy, KevinKevinBundyDrory, NivNivDroryHeckman, Timothy M.Timothy M.HeckmanLaw, David R.David R.LawRoman-Lopes, AlexandreAlexandreRoman-LopesPan, KaikeKaikePanSTANGHELLINI, LetiziaLetiziaSTANGHELLINIThomas, DanielDanielThomasWeijmans, Anne-MarieAnne-MarieWeijmansWestfall, Kyle B.Kyle B.Westfall2021-01-072021-01-0720160035-8711http://hdl.handle.net/20.500.12386/29574We study the spatially resolved excitation properties of the ionized gas in a sample of 646 galaxies using integral field spectroscopy data from the Sloan Digital Sky Survey IV Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) programme. Making use of Baldwin-Philips-Terlevich diagnostic diagrams we demonstrate the ubiquitous presence of extended (kpc scale) low-ionization emission-line regions (LIERs) in both star-forming and quiescent galaxies. In star-forming galaxies LIER emission can be associated with diffuse ionized gas, most evident as extraplanar emission in edge-on systems. In addition, we identify two main classes of galaxies displaying LIER emission: `central LIER' (cLIER) galaxies, where central LIER emission is spatially extended, but accompanied by star formation at larger galactocentric distances, and `extended LIER' (eLIER) galaxies, where LIER emission is extended throughout the whole galaxy. In eLIER and cLIER galaxies, LIER emission is associated with radially flat, low H α equivalent width of line emission (<3 Å) and stellar population indices demonstrating the lack of young stellar populations, implying that line emission follows tightly the continuum due to the underlying old stellar population. The H α surface brightness radial profiles are always shallower than 1/r<SUP>2</SUP> and the line ratio [O III] λ5007/[O II] λλ3727,29 (a tracer of the ionization parameter of the gas) shows a flat gradient. This combined evidence strongly supports the scenario in which LIER emission is not due to a central point source but to diffuse stellar sources, the most likely candidates being hot, evolved (post-asymptotic giant branch) stars. Shocks are observed to play a significant role in the ionization of the gas only in rare merging and interacting systems.STAMPAenArticle10.1093/mnras/stw12342-s2.0-84983757072000383481100060https://academic.oup.com/mnras/article/461/3/3111/26084762016MNRAS.461.3111BFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation::PE9_6 Stars and stellar systems