| 其他摘要 | The formation and evolution of galaxies has been the biggest challenge in astronomy and astrophysics. It can help us not only to understand the histories of galaxies but also to join the studies of stars and cosmology. Because most of observable mass of galaxies is contained in stars, the evolution of stars determines many integrated peculiarities of galaxies, e.g., luminosity, colours, and spectra. Therefore, one can investigate the formation and evolution of galaxies via studying the stellar contents of galaxies. The determination of stellar contents of galaxies has been a very important part of the studies of astronomy and astrophysics. Evolutionary population synthesis is just a powerful technique for the determination. The thesis investigate on a few key problems in the applications of evolutionary population synthesis technique. Some useful results are shown by our works. First, we investigate the ability of colours for determining the age and metallicity (hereafter stellar-population parameters) of stellar populations. The motivation is that it is difficult to measure the above parameters of distant (redshift > 0.3) galaxies via spectra-like methods, as these is no available spectra. However, colours are usually available for these galaxies. Our results show that colours can be used to determine stellar-population parameters. The best colour pairs for measuring stellar age and metallicity are shown, with possible result uncertainties. The results can help us to explore the stellar populations of distant galaxies, and then to give further investigations to the formation and evolution of galaxies. Second, because some observations showed that most galaxies including early-type ones have recent (within about 1 Gyr) star formations, and young populations can obviously affect the determination of stellar-population parameters, we investigate how young populations affect the determination of the ages and metallicities of populations. A statistical method for correcting the effects of young populations is brought forward by the work. Using this technique, we will be able to obtain the distributions and averages of the stellar-population parameters of a sample of galaxies. We also analyze the effects of young populations on the fundamental plane and Kormendy relation of galaxies. It shows that the scatter of the fundamental relations may be smaller when taking the effects of young populations into account, and we will measure less distances for galaxies after correcting for the effects of young populations. Third, because it is difficult to calculate the isochrones of binary stellar populations via stellar evolution code directly, we build a statistical isochrone database for conveniently and quickly modeling both single-star and binary-star populations. Then we calculate the spectral energy distributions, Lick indices, and colours of both single-star stellar populations and binary-star stellar populations. This makes it possible to conveniently take binary interactions into account when studying the formation and evolution of galaxies. Fourth, we investigate the effects of binary interactions on stellar population synthesis studies. The results show that binary interactions make the colours of populations bluer, Hbeta index larger, and metal line indices smaller. Using a Lick index method to determine stellar age and metallicity, we will obtain obviously less ages compared to the real values of populations. When taking a colour method to measure stellar-population parameters, we will get obviously less stellar metallicities. We also find that the real ages of populations are related to the values fitted via single stellar populations. Thus one can calculate the stellar ages fitted via binary-star stellar populations from the ages and metallicities fitted via single-star stellar populations. It is also shown that the relative results obtained by both single-star and binary-star stellar populations are similar. Fifth, we determine the stellar ages and metallicities of about 80 elliptical galaxies and test a new model for the formation of elliptical galaxies. Our results show some supports to the model, while show an opposition. The result is actually important for galaxy formation investigations. As a whole, the thesis solved some key problems on the applications of evolutionary population synthesis. It makes evolutionary population synthesis technique more powerful and useful in astrophysics studies. |
修改评论