arXiv 0810.56142008-10-31astro-ph

星系际尘埃及其光电加热

Intergalactic dust and its photoelectric heating

Akio K. Inoue, Hideyuki Kamaya

备注：: Earth, Planets and Space, special issue "Cosmic Dust" in press (paper presented in 5th annual meeting of the Asia-Oceania Geosciences Society, "Cosmic Dust" session); 16 pages and 6 figures

摘要：

本文研究了星系际介质中尘埃的光电加热。IGM的典型辐射场中的加热速率由$Γ_{\rm pe} = 1.2\times10^{-34}$ erg s $^{-1}$ cm $^{-3}$ $({\cal D}/10^{-4})(n_{\rm H}/10^{-5} {\rm cm^{-3}})^{4/3} (J_{\rm L}/10^{-21} {\rm erg s^{-1} cm^{-2} Hz^{-1} sr^{-1}})^{2/3} (T/10^4 {\rm K})^{-1/6}$表示，其中${\cal D}$是灰尘与气体的质量比，$n_{\rm H}$是氢数密度，$J_{\rm L}$是背景辐射的氢莱曼极限处的平均强度，并且$T$是气体温度，如果我们假设新的X射线光电产额模型由Weingartner等。（2006）和银河系中的尘埃尺寸分布由Mathis，Rumpl和Nordsieck（1977）。当氢数密度小于$\sim10^{-6}$ cm $^{-3}$ if ${\cal D}=10^{-4}$（银河系的1%）时，这种加热速率支配HI和HeII光电离加热速率，尽管加热速率比Weingartner和Draine（2001）的旧产额模型小2- 4倍。粒度分布非常重要。如果在IGM中仅存在大的（$\ge0.1$ $μ$ m）晶粒，则加热速率降低$\simeq5$倍。由于尘埃加热相对于光电离加热在低密度介质中更有效，因此可能导致Bolton等人（2008）提出的低密度IGM中的温度-密度关系倒置。最后，我们还发现在宇宙再电离前的平均IGM中，尘埃加热并不是很重要。

英文摘要：

We have examined the dust photoelectric heating in the intergalactic medium (IGM). The heating rate in a typical radiation field of the IGM is represented by $Γ_{\rm pe} = 1.2\times10^{-34}$ erg s$^{-1}$ cm$^{-3}$ $({\cal D}/10^{-4})(n_{\rm H}/10^{-5} {\rm cm^{-3}})^{4/3} (J_{\rm L}/10^{-21} {\rm erg s^{-1} cm^{-2} Hz^{-1} sr^{-1}})^{2/3} (T/10^4 {\rm K})^{-1/6}$, where ${\cal D}$ is the dust-to-gas mass ratio, $n_{\rm H}$ is the hydrogen number density, $J_{\rm L}$ is the mean intensity at the hydrogen Lyman limit of the background radiation, and $T$ is the gas temperature, if we assume the new X-ray photoelectric yield model by Weingartner et al. (2006) and the dust size distribution in the Milky Way by Mathis, Rumpl, & Nordsieck (1977). This heating rate dominates the HI and HeII photoionization heating rates when the hydrogen number density is less than $\sim10^{-6}$ cm$^{-3}$ if ${\cal D}=10^{-4}$ which is 1% of that in the Milky Way, although the heating rate is a factor of 2--4 smaller than that with the old yield model by Weingartner & Draine (2001). The grain size distribution is very important. If only large ($\ge0.1$ $μ$m) grains exist in the IGM, the heating rate is reduced by a factor of $\simeq5$. Since the dust heating is more efficient in a lower density medium relative to the photoionization heating, it may cause an inverted temperature--density relation in the low density IGM suggested by Bolton et al. (2008). Finally, we have found that the dust heating is not very important in the mean IGM before the cosmic reionization.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

摘要：

英文摘要：

相关论文