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arXiv 0905.1691astro-ph.CO
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高红移宇宙中尘埃的恒星源

Stellar sources of dust in the high redshift Universe

Rosa Valiante, Raffaella Schneider, Simone Bianchi, Anja C. Andersen

摘要:

为了研究恒星源是否可以解释由5<z<6.4类星体样品的mm/sub-mm观测推断的>10^8 Msun尘埃质量,我们发展了一个化学演化模型,该模型遵循金属和尘埃对恒星特征寿命的演化,考虑到尘埃的破坏机制。使用恒星尘埃网格作为初始质量和金属丰度的函数,40 Msun和0-1 Zsun的情况下,我们发现在高红移下AGB星在宇宙尘埃演化中的作用可能被忽略了.我们将含尘埃的化学演化模型应用于z=6.4的最远类星体SDSS J1148+ 5251的宿主星系.(i)Li et al.在数值模拟中获得的恒星形成历史。(2007)预测在z= 6.4时已经形成了一个大的恒星核球,(ii)如果远红外区的大部分光度是由年轻恒星产生的,那么恒星的形成速率为1000 Msun/yr,这与观测结果一致。AGB尘埃的贡献很大(80%)。当采用恒定的恒星形成率时,AGB尘埃的贡献减少到50%,但形成的尘埃总质量是一个小的因素2。两个模型预测的快速富集的ISM与金属和相对温和的碳丰度的演变,与观测的限制。这支持了恒星源可以解释观测到的尘埃的观点,但也表明AGB星对尘埃产生的贡献不能被忽视,即使是在目前观测到的最极端的红移下。

英文摘要:

With the aim of investigating whether stellar sources can account for the >10^8 Msun dust masses inferred from mm/sub-mm observations of samples of 5<z<6.4 quasars,we develop a chemical evolution model which follows the evolution of metals and dust on the stellar characteristic lifetimes, taking into account dust destruction mechanisms.Using a grid of stellar dust yields as a function of the initial mass and metallicity over the range 1-40 Msun and 0-1 Zsun,we show that the role of AGB stars in cosmic dust evolution at high redshift might have been over-looked.We apply the chemical evolution model with dust to the host galaxy of the most distant quasar at z=6.4, SDSS J1148+5251.Given the current uncertainties on the star formation history of the host galaxy, we have considered two models: (i) a star formation history obtained in a numerical simulation by Li et al.(2007) which predicts that a large stellar bulge is already formed at z=6.4,and (ii) a constant star formation rate of 1000 Msun/yr, as suggested by the observations if most of the FIR luminosity is due to young stars.The total mass of dust predicted at z=6.4 by the first model is 2x10^8Msun,within the range of values inferred by observations,with a substantial contribution (80%) of AGB-dust.When a constant star formation rate is adopted,the contribution of AGB-dust decreases to 50% but the total mass of dust formed is a factor 2 smaller.Both models predict a rapid enrichment of the ISM with metals and a relatively mild evolution of the carbon abundance,in agreement with observational constraints. This supports the idea that stellar sources can account for the dust observed but show that the contribution of AGB stars to dust production cannot be neglected, even at the most extreme redshifts currently accessible to observations.

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