本文選題：恒星 + 形成��； 參考：《天文學(xué)報(bào)》2017年02期

【摘要】："氣塵比"(Gas to Dust Ratio,GDR)是星際氣體與星際塵埃的質(zhì)量之比.廣泛認(rèn)同的銀河系氣塵比值是100-150.氣塵比值的大小不僅取決于星際環(huán)境,也與所考慮的塵埃成分相關(guān).恒星形成區(qū)是恒星形成的致密分子云區(qū)域,不同的分子云,其GDR也可能不同于普遍采用的數(shù)值.此工作選擇3個(gè)典型的恒星形成區(qū)進(jìn)行氣塵比的研究,它們分別是:大質(zhì)量恒星形成活躍的獵戶(hù)座(Orion)分子云,小質(zhì)量恒星形成區(qū)的代表金牛座(Taurus)分子云,極少或者無(wú)恒星形成活動(dòng)的Polaris分子云,對(duì)這3個(gè)天區(qū)的研究有利于了解不同輻射環(huán)境恒星形成區(qū)的氣塵比變化.在此對(duì)CO譜線(xiàn)積分強(qiáng)度與氫分子柱密度之間的轉(zhuǎn)換系數(shù)X_(CO)取常數(shù),以統(tǒng)計(jì)的方法計(jì)算了3個(gè)分子云的氣塵比N(H)/A_V,其值在Orion天區(qū)、Taurus天區(qū)和Polaris天區(qū)分別為25、38和55(單位:10~(20)cm~(-2).mag~(-1)),明顯高于之前人們給出的銀河系平均值.根據(jù)星際塵埃模型,將N(H)/A_v轉(zhuǎn)換成氣體塵埃的質(zhì)量比.采用被廣泛接受的WD01塵埃模型(V波段的選擇性消光比R_v=3.1的情況),得到3個(gè)恒星形成區(qū)的氣塵比分別為:160(Orion分子云)、243(Taurus分子云)、354(Polaris分子云),顯著高于普遍采用的彌漫星際介質(zhì)中100-150的取值范圍.恒星形成區(qū)的N(H)/A_v值高于平均值的另外一個(gè)可能的原因是,恒星形成區(qū)的塵埃由于吸積或者碰撞增長(zhǎng)變大,降低了V波段的單位質(zhì)量消光效率,而不是氣塵質(zhì)量比本身的增加.
[Abstract]:Gas to Dust GDR is the mass ratio of interstellar gas to interstellar dust. The widely accepted Milky way Gas-Dust ratio is 100-150. The ratio of gas to dust depends not only on the interstellar environment, but also on the dust composition considered. Star forming region is the dense molecular cloud region of star formation. The GDR of different molecular clouds may be different from the commonly used values. Three typical star forming regions were selected to study the gas-dust ratio: the active Orion molecular cloud for massive star formation and the Taurus molecular cloud for the small mass star formation region. For the Polaris molecular clouds with little or no star formation activity, the study of these three regions is helpful to understand the variation of the gas-dust ratio in the star forming regions in different radiation environments. In this paper, the conversion coefficient between the integral intensity of CO line and the density of hydrogen molecular column is taken as the constant. The gas / dust ratios of three molecular clouds are calculated by statistical method. The values of the gas / dust ratios of the three molecular clouds are 25 ~ 38 in the Orion sky region and 55 in the Polaris sky region, respectively, which are obviously higher than the Milky way average values given before. According to interstellar dust model, N(H)/A_v is converted to mass ratio of gas and dust. Using the widely accepted WD01 dust model, the selective extinction ratio (R_v=3.1) in V band is obtained. The ratio of gas to dust in three star forming regions is: 1: 160? O? O? Range of 100-150 values in the medium. Another possible reason that the N(H)/A_v value of the star forming region is higher than the average is that the dust in the star forming region increases due to accretion or collision, which reduces the extinction efficiency per unit mass in V band, rather than the increase of the gas-dust mass ratio itself.
【作者單位】： 北京師范大學(xué)天文系;
【基金】：國(guó)家自然科學(xué)基金項(xiàng)目(11373015,11533002) 973項(xiàng)目(2014CB845702) 中央高�；究蒲袠I(yè)務(wù)費(fèi)專(zhuān)項(xiàng)資助
【分類(lèi)號(hào)】：P152

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