Life and times of dwarf spheroidal galaxies
Life and times of dwarf spheroidal galaxies
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矮椭球星系的寿命和时代
DOI：
10.1111/j.1365-2966.2008.13035.x
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发表时间：
2008
影响因子：
4.8
通讯作者：
InafOaa
中科院分区：
文献类型：
--
作者：
S. Salvadori;A. Ferrara;R. S. SissaIsas;InafOaa
我们提出了一个关于矮球星系(DSphs)、银河系卫星(MW)的形成和演化的宇宙学假说。半分析程序Gamete(Galaxy Merger Tree And Evolution)的一个改进版本被用来跟踪dSphs的演化和MW形成的同时，与观测到的两者的性质相匹配。在这个场景中，dSph星系代表了在微波环境中在z=7.2±0.7(即在预电离时代z>；zrei=6)活化化的化石天体，在那个时期已经被预富集到[Fe/H]∼−3；它们的动力学质量在狭窄的范围M=(1.6±0.7)×10 8M�，尽管更精细的再电离处理可能会引入更大的扩散。在这样的低质量天体中，机械反馈效应非常显著，导致气体∼100Myr在形成纪元后完全喷发：99%的今天恒星质量M∗=(3±0.7)×106M�是在这个演化阶段形成的，即它们的年龄为13 Gyr。随后，恒星形成被演化恒星返回的气体重新点燃，第二次喷发发生。这个周期大约持续1Gyr，在此期间恒星形成是断断续续的。在z=0时，dSph气体含量为mg=(2.6 8±0.97)×10 4M�。我们的结果与用作dSphs模板的Sculptor的几个观测性质相匹配：(I)金属丰度分布函数；(Ii)色等图；(Iii)[Fe/H]和GT；−1.5的恒星[O/Fe]丰度比的减小；(Iv)暗物质含量和光质比；(V)HI气体质量含量。
We propose a cosmological scenario for the formation and evolution of dwarf spheroidal galaxies (dSphs), satellites of the Milky Way (MW). An improved version of the semi-analytical code GAMETE (GAlaxy Merger Tree and Evolution) is used to follow the dSphs evolution simultaneously with the MW formation, matching the observed properties of both. In this scenario dSph galaxies represent fossil objects virializing at z = 7.2 ± 0.7 (i.e. in the prereionization era z > zrei = 6) in the MW environment which at that epoch has already been pre-enriched up to [Fe/H] ∼− 3; their dynamical masses are in the narrow range M = (1.6 ± 0.7) × 10 8 M� , although a larger spread might be introduced by a more refined treatment of reionization. Mechanical feedback effects are dramatic in such low-mass objects, causing the complete blow-away of the gas ∼100 Myr after the formation epoch: 99 per cent of the present-day stellar mass, M∗ = (3 ± 0.7) × 10 6 M� , forms during this evolutionary phase, i.e. their age is >13 Gyr. Later on, star formation is re-ignited by returned gas from evolved stars and a second blow-away occurs. The cycle continues for about 1 Gyr during which star formation is intermittent. At z = 0 the dSph gas content is Mg = (2.68 ± 0.97) × 10 4 M� . Our results match several observed properties of Sculptor, used as a template of dSphs: (i) the metallicity distribution function; (ii) the colour‐magnitude diagram; (iii) the decrement of the stellar [O/Fe] abundance ratio for [Fe/H] > −1.5; (iv) the dark matter content and the light-to-mass ratio; (v) the H I gas mass content.