大样本恒星演化研究组知识库

Radiation fields emitted by O- and B-type stars or young stellar populations (SPs) are generally considered as significant central ionizing sources (CISs) of classic H II regions. In our previous studies, we showed that the inclusion of binary interactions in stellar population synthesis models can significantly increase the ultraviolet spectrum hardness and the number of ionizing photons of intermediate-age (IA) SPs (7 less than or similar to log(t/yr) less than or similar to 8). In this work, we present photoionization models of H II regions ionized by radiation fields emitted by IA SPs, including binary systems, and show that these fields are in theory possible candidates for significant CISs of classic H II regions. When radiation fields of IA SPs comprising binary systems are used as the CISs of classic H II regions, the theoretical strengths of a number of lines (such as [O III] lambda 4959', [ S II] lambda 6716', etc.), which are weaker than observations, are increased; the border or selection-criterion lines between star-forming galaxies and active galactic nuclei (AGNs) in the diagnostic diagrams (for example, [N II] lambda 6583/H alpha versus [O III] lambda 5007/H beta), move into the region occupied originally by AGNs; and the He II lambda 1640 line, observed in Lyman break and high-redshift gravitationally lensed galaxies, also can be produced.