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A new progress was made in early-type galaxies [ETGs] research
2016-09-05| 【A A A【Print】【Close】

  Dr. Zhang Yu at Xinjiang Astronomical Observatory (XAO) investigates the effects of binary interactions on parameter determinations for early-type galaxies [ETGs], by using the evolutionary population synthesis (EPS) model, and combine with the ultraviolet and optical observation data of GALEX and SDSS survey.

  For the distant galaxies, we can only get their integration information. EPS is one of the techniques to study the property and evolution of galaxies. Most EPS models are still neglect the effect of binary interactions, while binary stars have strong radiation on the UV pass band, which is similar to the effect of young stars. Therefore, neglecting binaries in the EPS models can lead to an underestimation of the flux in the UV pass band and then affect the determination of parameters for galaxies.

  Researchers use the EPS models with (BSP) and without (BSP) binary interactions to investigate the ETGs, analyze the effects of binary interactions on the parameter determinations for ETGs. They found that the inclusion of binary interactions could affect age determinations, and have negligible effect on the metallicity. For all ETGs, the early evolution stage is a very important period for star formation for SSP and BSP models, most of the stars are formed at the early evolution epoch. From the comparison of star formation history estimates between the SSP and BSP models, they found the binary interactions could affect the late evolution stage for some ETGs with strong UV emission. The reason is that the binary interactions can enhance the UV flux. So it is necessary to take binary interactions into account in the EPS models for ETG studies.

           We adopt two ESP models to gain the star formation history on three ETGs

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