Ionization of the diffuse gas in galaxies: Hot low-mass evolved stars at work

Дата и время публикации : 2011-04-04T10:49:45Z

Авторы публикации и институты :
Nahiely Flores-Fajardo
Christophe Morisset
Grazyna Stasinska
Luc Binette

Ссылка на журнал-издание: Monthly Notices of the Royal Astronomical Society, 2011, Volume 415, Issue 3, pp. 2182-2192
Коментарии к cтатье: Accepted for publication in MNRAS
Первичная категория: astro-ph.GA

Все категории : astro-ph.GA

Краткий обзор статьи: We revisit the question of the ionization of the diffuse medium in late type galaxies, by studying NGC 891, the prototype of edge-on spiral galaxies. The most important challenge for the models considered so far was the observed increase of [OIII]/Hbeta, [OII]/Hbeta, and [NII]/Halpha with increasing distance to the galactic plane. We propose a scenario based on the expected population of massive OB stars and hot low-mass evolved stars (HOLMES) in this galaxy to explain this observational fact. In the framework of this scenario we construct a finely meshed grid of photoionization models. For each value of the galactic latitude z we look for the models which simultaneously fit the observed values of the [OIII]/Hbeta, [OII]/Hbeta, and [NII]/Halpha ratios. For each value of z we find a range of solutions which depends on the value of the oxygen abundance. The models which fit the observations indicate a systematic decrease of the electron density with increasing z. They become dominated by the HOLMES with increasing z only when restricting to solar oxygen abundance models, which argues that the metallicity above the galactic plane should be close to solar. They also indicate that N/O increases with increasing z.

Category: Physics