Interpreting the ionization sequence in star-forming galaxy emission-line spectra
| Autor: | Gary J. Ferland, James T. Allen, Helen Meskhidze, Anthony Crider, Paul C. Hewett, Jack A. Baldwin, Chris T. Richardson |
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| Rok vydání: | 2016 |
| Předmět: |
Luminous infrared galaxy
Physics 010308 nuclear & particles physics Surface brightness fluctuation FOS: Physical sciences Astronomy and Astrophysics Astrophysics::Cosmology and Extragalactic Astrophysics Astrophysics Astrophysics - Astrophysics of Galaxies 01 natural sciences Galaxy Space and Planetary Science Astrophysics of Galaxies (astro-ph.GA) Ionization 0103 physical sciences Elliptical galaxy Brightest cluster galaxy Atomic physics Interacting galaxy 010303 astronomy & astrophysics Lenticular galaxy Astrophysics::Galaxy Astrophysics |
| Zdroj: | Monthly Notices of the Royal Astronomical Society. 458:988-1012 |
| ISSN: | 1365-2966 0035-8711 |
| DOI: | 10.1093/mnras/stw100 |
| Popis: | High ionization star forming (SF) galaxies are easily identified with strong emission line techniques such as the BPT diagram, and form an obvious ionization sequence on such diagrams. We use a locally optimally emitting cloud model to fit emission line ratios that constrain the excitation mechanism, spectral energy distribution, abundances and physical conditions along the star-formation ionization sequence. Our analysis takes advantage of the identification of a sample of pure star-forming galaxies, to define the ionization sequence, via mean field independent component analysis. Previous work has suggested that the major parameter controlling the ionization level in SF galaxies is the metallicity. Here we show that the observed SF- sequence could alternatively be interpreted primarily as a sequence in the distribution of the ionizing flux incident on gas spread throughout a galaxy. Metallicity variations remain necessary to model the SF-sequence, however, our best models indicate that galaxies with the highest and lowest observed ionization levels (outside the range -0.37 < log [O III]/H\b{eta} < -0.09) require the variation of an additional physical parameter other than metallicity, which we determine to be the distribution of ionizing flux in the galaxy. 41 pages, 17 figures, 9 tables, accepted to MNRAS |
| Databáze: | OpenAIRE |
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