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arXiv 1407.0022astro-ph.GAastro-ph.CO
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DM模型的微弱侏儒测试:WDM与CDM

Faint dwarfs as a test of DM models: WDM vs. CDM

Fabio Governato, Daniel Weisz, Andrew Pontzen, Sarah Loebman, Darren Reed, Alyson M. Brooks, Peter Behroozi, Charlotte Christensen, Piero Madau, Lucio Mayer, Si… 展开作者

Fabio Governato, Daniel Weisz, Andrew Pontzen, Sarah Loebman, Darren Reed, Alyson M. Brooks, Peter Behroozi, Charlotte Christensen, Piero Madau, Lucio Mayer, Sijing Shen, Matthew Walker, Thomas Quinn, Benjamin W. Keller, James Wadsley

摘要:

我们使用高分辨率的Hydro $+$ N体宇宙学模拟来比较小场矮星(恒星质量~ 10 $^{6-7}$ M $\odot$,总质量10 $^{10}$ M $\odot$)在$Λ$主导的CDM和2 keV WDM宇宙学中的组装和演化.我们发现,在WDM模型中的恒星形成(SF)减少和延迟1-2 Gyr相对于CDM模型,独立的SF和反馈的细节。独立于DM模型,但与SF效率成比例,气体流出通过“动态加热”降低中心质量密度,使得所有实现在500 $~$ pc时具有20 km的圆周速度$<$,与局部运动学约束一致。由于动态加热,较老的恒星比较年轻的恒星在中心集中程度较低,类似于在附近矮星系中观察到的恒星种群梯度。介绍了一个重要的诊断SF和反馈模型,我们将我们的模拟人工色星等图和恒星形成的历史,以直接比较现有的观测。模拟的星系在许多$\sim$ 1000万年长的爆发中形成了它们的大部分恒星。CDM星系有一个全球SFH,HI丰度和Fe/H和α-元素分布以及匹配到目前的观测矮星系。这些结果突出了在模拟中直接包括“重子物理学”的重要性:1)将星系形成模型的预测与本地矮星系的运动学和数密度进行比较; 2)区分CDM和具有不同DM或功率谱的非标准模型。

英文摘要:

We use high resolution Hydro$+$N-Body cosmological simulations to compare the assembly and evolution of a small field dwarf (stellar mass ~ 10$^{6-7}$ M$\odot$, total mass 10$^{10}$ M$\odot$ in $Λ$ dominated CDM and 2keV WDM cosmologies. We find that star formation (SF) in the WDM model is reduced and delayed by 1-2 Gyr relative to the CDM model, independently of the details of SF and feedback. Independent of the DM model, but proportionally to the SF efficiency, gas outflows lower the central mass density through `dynamical heating', such that all realizations have circular velocities $<$ 20kms at 500$~$pc, in agreement with local kinematic constraints. As a result of dynamical heating, older stars are less centrally concentrated than younger stars, similar to stellar population gradients observed in nearby dwarf galaxies. Introducing an important diagnostic of SF and feedback models, we translate our simulations into artificial color-magnitude diagrams and star formation histories in order to directly compare to available observations. The simulated galaxies formed most of their stars in many $\sim$10 Myr long bursts. The CDM galaxy has a global SFH, HI abundance and Fe/H and alpha-elements distribution well matched to current observations of dwarf galaxies. These results highlight the importance of directly including `baryon physics' in simulations when 1) comparing predictions of galaxy formation models with the kinematics and number density of local dwarf galaxies and 2) differentiating between CDM and non-standard models with different DM or power spectra.

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