本文選題：銀河系 + 恒星　； 參考：《河北師范大學(xué)》2016年碩士論文

【摘要】：太陽鄰域的F型和G型矮星被看做是能反映銀河系化學(xué)演化歷史的“活化石”,其化學(xué)豐度對我們了解銀河系的起源和演化過程有著重要意義。我們的工作就是通過觀測這類恒星中各種元素的化學(xué)豐度,研究恒星的化學(xué)演化,進(jìn)而探究銀河系的結(jié)構(gòu)和化學(xué)演化。利用中國科學(xué)院國家天文臺興隆觀測基地的2.16米望遠(yuǎn)鏡及其附屬的光纖攝譜儀(HRS),觀測獲得了來自Geneva-Copenhagen Survey(GSC)星表的100顆太陽鄰域的F型和G型矮星的高分辨率(R≈40000)、高信噪比(S/N≥100)光譜。采用IRAF軟件包進(jìn)行一維光譜的抽取和等值寬度的測量,并利用Kurucz的局部熱動平衡大氣模型,利用ABUNTEST8程序包分別計(jì)算出100顆樣本星的Na、Mg、Al、Si、Ca、Ti、Cr、Ni、Fe、Zn、Y、Ba、O等13種元素的化學(xué)豐度。結(jié)合恒星運(yùn)動學(xué)的星族成分劃分標(biāo)準(zhǔn)、恒星年齡、恒星平均軌道半徑及離開銀道面的距離等相關(guān)信息,分析了不同星族成分的元素豐度分布,得到了以下主要結(jié)論。(1)薄盤恒星和厚盤恒星的ɑ元素(Mg、Si、Ca、Ti、O)豐度不能完全分開,在我們的樣本范圍中,既存在運(yùn)動學(xué)屬于薄盤,但[α/Fe]屬于厚盤的恒星,也存在運(yùn)動學(xué)屬于厚盤,但[α/Fe]屬于薄盤的恒星。厚盤星的[α/Fe]整體高于薄盤星的[α/Fe],但是在-0.7≤[Fe/H]≤-0.3的范圍內(nèi)存在較為嚴(yán)重的混合。(2)薄盤星和厚盤星的[O/Fe]無明顯分離,但厚盤星的O元素豐度平均高于薄盤星,且元素豐度隨金屬豐度的增加而持續(xù)減小,這一現(xiàn)象存在于整個(gè)樣本范圍內(nèi),并且在[Fe/H]=-0.3附近存在膝狀下降(knee)現(xiàn)象。(3)對于鐵族元素(Cr、Ni、Zn),各元素的豐度分布并不完全一致,Cr和Ni的元素豐度整體在零附近。對于這三種元素,樣本中的厚盤星的元素豐度沒有整體高于薄盤星的趨勢,且薄、厚盤的恒星存在明顯混合,從元素豐度上很難將二者區(qū)分開。(4)對于奇Z元素(Na、Al)來說,我們的結(jié)果表明[Na/Fe]基本上與鐵族元素的演化趨勢一致,整體上與[Fe/H]沒有相關(guān)性,且厚盤和薄盤恒星的[Na/Fe]也沒有明顯區(qū)分,但對[Fe/H]0的富金屬盤星,[Na/Fe]表現(xiàn)出隨金屬豐度的增加而略微增加的趨勢。[Al/Fe]隨[Fe/H]的關(guān)系和ɑ元素相似,厚盤星的豐度平均高于薄盤恒星。(5)中子俘獲元素(Ba、Y)的元素豐度在薄盤和厚盤恒星之間同樣存在明顯混合,且Ba和Y有著相近的豐度分布,與ɑ元素明顯不同的是,其薄盤星的豐度普遍高于厚盤星的豐度,且薄盤星的豐度彌散更大。(6)在太陽附近的內(nèi)盤,厚盤恒星存在一個(gè)負(fù)的[ɑ/Fe]徑向豐度梯度,而對外盤的厚盤恒星而言,隨著Rm的增加,厚盤恒星的[ɑ/Fe]豐度又會微弱增加。而薄盤恒星的[ɑ/Fe]存在一個(gè)正的徑向豐度梯度。盡管薄盤和厚盤恒星的[ɑ/Fe]沒有一個(gè)確切的分界,但平均來講厚盤恒星的[ɑ/Fe]要高于薄盤。(7)薄盤星和厚盤星在Z方向也無法完全分開,樣本中的薄盤星主要分布在Zmax≤0.5kpc的范圍內(nèi),厚盤星則在0kpc≤Zmax≤2kpc的范圍內(nèi)分布的比較均勻。(8)關(guān)于恒星年齡和金屬豐度,樣本中的厚盤星的年齡整體高于薄盤星,且ɑ元素豐度隨恒星年齡的增加而增加,所以存在恒星年齡-金屬豐度關(guān)系。這些結(jié)果表明,雖然薄盤星和厚盤星的元素豐度在統(tǒng)計(jì)平均的結(jié)果上存在差異,但我們無法通過元素豐度把薄盤恒星和厚盤恒星準(zhǔn)確的區(qū)分開,即使對于ɑ元素也是如此,在[Fe/H]=-0.5附近豐度存在嚴(yán)重混合。因此,對于不同星族元素豐度能否準(zhǔn)確區(qū)分,以及通過運(yùn)動學(xué)特征劃分星族成分的可靠性,仍然需要更多的樣本來進(jìn)行進(jìn)一步的研究。
[Abstract]:The F and G dwarfs of the solar neighborhood are regarded as "living fossils" that reflect the history of the Milky Way's chemical evolution. Their chemical abundance is of great significance to our understanding of the origin and evolution of the Milky way. Our work is to investigate the chemical evolution of stars by observing the chemical abundance of various elements in these stars. The structure and chemical evolution of the Milky way. Using the 2.16 meter telescope and its attached optical fiber spectrograph (HRS) of the National Astronomical Observatory, the National Astronomical Observatory of the National Astronomical Observatory, the high resolution (R) 40000 and the high signal to noise ratio (S/N > 100) spectrum of 100 F and G dwarfs from the solar neighborhood of the Geneva-Copenhagen Survey (GSC) star are observed. Using the IRAF software package for the extraction of one dimensional spectrum and the measurement of the equivalent width, and using the local thermal equilibrium atmosphere model of Kurucz, the ABUNTEST8 program package is used to calculate the chemical abundances of the 13 elements, such as the Mg, Al, Si, Ca, Ti, Cr, Ni, Fe, Cr, Ni, Fe, Cr, Ni, and star composition of stellar kinematics. Age, the average orbital radius of the star and the distance away from the silver channel, analysis the distribution of the element abundances of different star groups, and get the following main conclusions. (1) the abundance of Mg, Si, Ca, Ti, O in the thin disk star and the thick disk star can not be completely separated. In our sample range, the existing kinematics belongs to the thin disk, but [alpha /F] E] is a thick disk star, and the kinematics belongs to the thick disk, but [alpha /Fe] belongs to the thin disk star. [alpha /Fe] as a whole is higher than that of thin disc [alpha] /Fe], but in -0.7 < < [Fe/H] < -0.3 > there is a more serious mixture. (2) the [O/Fe] of the thin disc star and the thick disc star is not clearly separated, but the abundance of the O element in the thick disk star is higher than that of thin. Disc star, and the element abundance continues to decrease with the increase of metal abundance, this phenomenon exists in the whole sample range, and there is a geniculate descent (knee) phenomenon near [Fe/H]=-0.3. (3) for the iron element (Cr, Ni, Zn), the abundance distribution of each element is not completely consistent, and the element abundances of Cr and Ni are in the vicinity of zero. For these three elements The element abundance of the thick disk stars in the sample has no overall higher than the trend of the thin disc star, and the thin, thick disk stars have a distinct mixture, and it is difficult to separate the two from the element abundance. (4) for the odd Z element (Na, Al), our results show that the [Na/Fe] is basically consistent with the evolution trend of the iron element, and is not related to [Fe/H] as a whole. The [Na/Fe] of the thick disk and thin disk star has no obvious distinction, but for the [Fe/H]0 rich metal disk star, the [Na/Fe] shows a slight increase with the increase of the metallicity, and the.[Al/Fe] is similar to the [Fe/H]. The abundance of the thick disk star is higher than that of the thin disk star. (5) the element abundance of the medium subtrapping element (Ba, Y) is in the thin disk and the thick disk. The same obvious mixture between the stars and Ba and Y has a similar abundance distribution. The abundance of the thin disc stars is generally higher than the abundance of the thick disc stars, and the abundance of the thin disc stars is greater. (6) there is a negative /Fe] radial abundance gradient in the inner disk near the sun, and the thick disk of the outer disk is constant. In the star, with the increase of Rm, the /Fe] abundance of the thick disk star will be slightly increased. The [/Fe]] of the thin disk star has a positive radial abundance gradient. Although there is no exact dividing line between the thin disk and the thick disk star, the /Fe] of the thick disk star is higher than the thin disk. (7) the thin disc star and the thick disk star are not in the direction of Z. The thin disc star in the sample is mainly distributed in the range of Zmax < 0.5kpc, and the thick disc star is more evenly distributed in the range of 0kpc < Zmax < < 2kpc. (8) the age of the star and the abundance of metal, the age of the thick disc star in the sample is higher than that of the thin star, and the abundance of the element increases with the age of the star. Star age metallicity relations. These results show that although the element abundances of thin disc stars and thick disc stars differ in statistical mean results, we can not separate the thin disk stars from the thick disk stars by the abundance of elements, and even for the elements, there is a serious mixture in the abundance near [Fe/H]=-0.5. Therefore, More samples are still needed for further research on whether the abundance of different family elements can be accurately differentiated and the reliability of the star composition is divided by kinematic characteristics.
【學(xué)位授予單位】：河北師范大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：P152;P148

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