| M31 (Andromeda galaxy) is the biggest spiral in the Local Group. We have established an infall-based model of disc formation in order to study the star formation history (SFH) and chemo-photometric evolution properties of the M31 disc. We are interested in the galaxy disc because disc is the major component of galaxy and has most of baryon matter in it. Based on a phenomenological model of galaxy formation, and by comparing the model predictions with observational data we are able to understand some physical properties of M31 disc, such as disk star formation history and disc formation time scale.In the first part of the thesis, we have summarized the most recent observational and research progress for each component of M31,including nucleus, bulge, disc and halo. Similarity and difference of observational features are discussed between M31 and the Milky Way. Their formation mechanism is also compared. And their basic observational data are given.In the second part, we give the detailed infall model of M31 disc, which assumes that disc is formed by falling of gas with primordial chemical component. Two infall time-scales, ( and t0 are introduced considering different gas-cooling time-scale. Both time scales are assumed to be function of the distance from disc center. Different t0 means that time of starting gas infall is different in different position of M31 disc. And different ( means that infall time-scale is different in different radius of disc. We assume that t0 is the linear function of the distance and ( is increased by exponential with radius. Both of them indicate that disc is formed inside-out. Star formation rate (SFR) is the most important parameter studying galaxy formation and evolution. Kennicutt law is usually adopted, which expresses that SFR is proportional to N power law of gas surface mass density with N = 1.4. This kind of SFR is the mean value of observation of nearby galaxy. But for a specific galaxy, SFR in different radius may have different properties. We have considered three kinds of SFR: (1) SFRâ… : SFR proportional to gas surface mass density with N = 1. (2) SFRâ…¡: Kennicutt law with N = 1.4. (3) SFRâ…¢: SFR correlated with gas surface mass density and angular velocity with N = 1. We have compared different model results, which derived from different SFR. Our results show that the predictions of the model with SFRâ… fits observation data better than those of model with other kinds of SFR, including scale-length in 5 different band U,B,V,R,K, gas distribution and metal abundance profile. Subsequently, color gradient and evolution are discussed using evolutionary population synthesis method. The prediction of our best-fit model for color profile is not in well agreement with observational data. The main reason is the extinction effect including internal extinction of M31 and foreground extinction of the Milky Way. Additionally, bulge contribution for color is also important. So a reasonable extinction model and bulge formation model are necessary to correct either our model predictions or observational data.Finally, we have given a brief discussion of the effect of M31 bulge, which is assumed to be formed by disc instability since M31 has a big bulge. |
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