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arXiv 1206.0336astro-ph.CO
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大质量中微子促进早型半导体的尺寸增长

Massive Neutrinos Promote the Size Growth of Early-Type Galaxies

Hyunmi Song, Jounghun Lee

摘要:

利用强半解析公式,通过追踪星系祖先的合并历史,研究了大质量中微子对早型星系(ETG)大小($R_{e}$)和恒星质量($M_{\star}$)演化的影响.我们发现,作为大质量中微子的存在起着提高每个晕的平均合并率的作用,高$z$祖先的后代星系具有固定的质量演化更迅速的尺寸为$Λ$ MDM($Λ$ CDM +大质量中微子)模型比$Λ$ CDM的情况。当中微子质量分数为$f_ν=0.05$时,祖先星系$R_{e}[M_{\star}/(10^{11}M_{\odot})]^{-0.57}\propto (1+z)^{-β}$的质量标准化尺寸演化随$β\sim 1.5$的幂律指数变化很陡;当中微子质量分数为$f_ν=0$时,随$β\sim 1$的幂律指数变化很陡。如果适当考虑大质量中微子的存在和作用,可以解释高$z$ ETG相对于具有相似恒星质量的局域椭圆星系的异常致密性.

英文摘要:

The effect of massive neutrinos on the evolution of the early type galaxies (ETGs) in size ($R_{e}$) and stellar mass ($M_{\star}$) is explored by tracing the merging history of galaxy progenitors with the help of the robust semi-analytic prescriptions. We show that as the presence of massive neutrinos plays a role of enhancing the mean merger rate per halo, the high-$z$ progenitors of a descendant galaxy with fixed mass evolves much more rapidly in size for a $Λ$MDM ($Λ$CDM + massive neutrinos) model than for the $Λ$CDM case. The mass-normalized size evolution of the progenitor galaxies, $R_{e}[M_{\star}/(10^{11}M_{\odot})]^{-0.57}\propto (1+z)^{-β}$, is found to be quite steep with the power-law index of $β\sim 1.5$ when the neutrino mass fraction is $f_ν=0.05$, while it is $β\sim 1$ when $f_ν=0$. It is concluded that if the presence and role of massive neutrinos are properly taken into account, it may explain away the anomalous compactness of the high-$z$ ETGs compared with the local ellipticals with similar stellar masses.

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