本文關(guān)鍵詞： 星系 化學(xué)-顏色演化 恒星形成歷史 M33　出處：《中國科學(xué)院研究生院（云南天文臺）》2012年碩士論文　論文類型：學(xué)位論文

【摘要】：M33(NGC598)是本星系群中最小的旋渦星系，其重子物質(zhì)質(zhì)量僅約為銀河系的十分之一，中心無顯著核球，旋臂結(jié)構(gòu)較為完整，在其演化歷史中沒有并合和其它相互作用的跡象。由于它適當(dāng)?shù)木嚯x和角直徑以及相對較小的傾角，使得氣體和星族的徑向分布觀測成為可能，從理論上對它進(jìn)行詳細(xì)研究，有利于我們進(jìn)一步理解小質(zhì)量旋渦星系的形成及演化過程。 唯象模型被廣泛應(yīng)用于本星系群中銀河系等旋渦星系的化學(xué)演化研究中，在理解這些星系的演化方面取得了一定的進(jìn)展，但之前的模型仍然有一些不足之處，其主要包括以下幾個方面：(I)沒有分開計算分子氫氣體和原子氫氣體；(II)采用的恒星形成律與總的氣體面密度相關(guān)；(III)沒有考慮外流。然而，這些因素直接影響到星系的演化歷史。首先，分子氫氣體和原子氫氣體對于星系中發(fā)生各個物理過程至關(guān)重要，并且近年來星系中分子氫和原子氫等冷氣體成分的觀測數(shù)據(jù)逐漸增多，所以有必要分開計算分子氫氣體和原子氫氣體來嚴(yán)格約束模型。其次，由于恒星形成于巨分子云中，所以恒星形成律應(yīng)該與分子氫氣體面密度更相關(guān)。最后，M33是小質(zhì)量的旋渦星系，，勢阱淺，容易受到超新星爆發(fā)等因素的影響而引發(fā)外流，故外流必不可少。 為了解決以上問題，以銀河系的化學(xué)演化模型為參照，我們重新構(gòu)建了盤狀星系M33形成和演化的化學(xué)-顏色演化模型，在模型中同時考慮了氣體內(nèi)落和外流的影響，分開計算了星系盤中分子氣體和原子氣體成分，使用了與分子氫氣體面密度相關(guān)的恒星形成律。其中內(nèi)落采用了吸積模型的形式來描述星系盤的增長過程，而外流速率與恒星形成率成正比；星系盤中分子氣體和原子氣體成分的物理模型使用了分子氣體比例與星際壓強(qiáng)相關(guān)的模型來描述分子氫氣體與原子氫氣體的轉(zhuǎn)換；恒星形成律采用了Leroy et al.(2008)[1]的與分子氫氣體面密度成正比的恒星形成律來描述冷氣體轉(zhuǎn)化為恒星的速率。模型中引入兩個自由參數(shù)：內(nèi)落時標(biāo)τ和外流效率bout。 利用我們建立的模型，詳細(xì)計算了M33盤的分子氫氣體、原子氫氣體、總氣體、SFR、O元素豐度、FUV波段和K波段的表面亮度及FUV K顏色等參量的徑向輪廓，通過將模型預(yù)言與近年來的觀測結(jié)果進(jìn)行比較，從而進(jìn)一步理解星系盤的恒星形成歷史的主要特征。得出了如下結(jié)論：(i) M33的恒星形成效率比Leroy et al.(2008)[1]的較大質(zhì)量的近鄰旋渦星系的平均值大，這點(diǎn)與前人的觀測結(jié)果一致；(ii) M33是通過原初氣體內(nèi)落逐漸形成的，并且模型預(yù)言的結(jié)果對內(nèi)落時標(biāo)很敏感，內(nèi)落時標(biāo)越長，分子氫、原子氫及總氣體面密度和SFR越高，顏色越藍(lán)，金屬豐度越低，而外流主要影響盤的金屬豐度；(iii)當(dāng)模型采用較為適中的外流效率和“由內(nèi)到外”的形成圖像時，模型預(yù)言的結(jié)果能夠很好地重現(xiàn)M33的大部分觀測特征；(iv)與經(jīng)典的K-S SF Law相比，與分子氫氣體面密度相關(guān)的SF-Law將更適合于描述盤星系的演化，特別是冷氣體及星族的徑向面密度分布。
[Abstract]:M33 (NGC598) is the smallest spiral galaxy in the local group, the baryon mass is only about 1/10 of the Milky Way center, no significant nuclear ball arm structure is complete, in its evolutionary history and no interaction and other signs. Because of its proper distance and angle and diameter is relatively small the angle that the radial distribution of gas and stars can be observed, detailed research on it from theory, conducive to further our understanding of the formation and evolution process of small mass of spiral galaxies.
Study on the chemical evolution of the phenomenological model has been widely applied in the Milky Way this galaxy group series of spiral galaxies, some progress has been made in understanding the evolution of these galaxies, but before the model still has some shortcomings, which include the following: (I) there is no separate calculation of molecular and atomic hydrogen gas hydrogen gas; (II) the star formation law and the total gas surface density; (III) does not consider the outflow. However, these factors directly affect the evolution of galaxies. Firstly, molecular hydrogen gas and hydrogen gas is essential for various physical processes in galaxies, and the observation data of cold gas in recent years the galaxy in molecular hydrogen and hydrogen atoms were gradually increased, so it is necessary to separate the calculation of molecular hydrogen gas and atomic hydrogen gas to strict constraint model. Secondly, the star formation in the giant molecular cloud The law of star formation should be more related to the surface density of molecular hydrogen. Finally, M33 is a small mass spiral galaxy with shallow potential and outflow due to the influence of supernovae and other factors. Therefore, the outflow is essential.
In order to solve the above problems, according to the Milky Way Department of chemical evolution model, we constructed M33 disk galaxy formation and evolution of the chemical evolution of color model, the model takes into account the gas infall and outflow, the galactic disk of molecular gas and atom gas components separately, the formation of the use of the relevant law with the molecular gas density in the decent stars. The falling accretion model to describe the growth process of the galactic disk, and the outflow rate and the rate of star formation is proportional to the physical model of galaxies; conversion of molecular gas and atomic gas components used to model gas molecules associated with the proportion of interstellar pressure to describe the molecular hydrogen gas and atomic hydrogen gas; star formation law by Leroy et al. (2008) [1] stars with molecular hydrogen gas surface density is proportional to the formation of law to describe the cold gas into Star rate. The introduction of two free parameters in the model: in the fall when the standard tau and outflow efficiency of bout.
Using our model, molecular hydrogen gas M33 disk is calculated in detail, atomic hydrogen gas, total gas, SFR, O element abundances, the radial profile of FUV band and K band FUV K color surface brightness and other parameters, the model predicted results are compared with observations in recent years, in order to further understand the formation the main feature of the history of the Galactic disc stars. Conclusions are drawn as follows: (I) M33 star formation efficiency than Leroy (2008) et al. [1] of the neighboring spiral galaxies average, this observation results agree with previous results; (II) M33 is the primordial gas in falling gradually, and the results predicted by the model is very sensitive to the fall time scale, fall time scale is longer, molecular hydrogen, hydrogen atoms and total gas density and the higher the decent SFR, color is blue, the metallicity is lower, and the outflow of main influence disc metal abundance; (III) when using model A more modest outflow rate and formation of the "image from the inside to the outside", most of the features observed results predicted by the model can well reproduce the M33; (IV) compared with the classical K-S SF Law evolution related to molecular hydrogen decent density of SF-Law will be more suitable for describing disc galaxies, especially radial the surface density distribution of cold gas and stars.

【學(xué)位授予單位】：中國科學(xué)院研究生院（云南天文臺）
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2012
【分類號】：P152

【參考文獻(xiàn)】

相關(guān)博士學(xué)位論文 前1條

1 羅智堅;盤狀星系形成和演化的半解析研究[D];中國科學(xué)院研究生院（上海天文臺）;2004年

本文編號：1528663