Cuspy No More: How Outflows Affect the Central Dark Matter and Baryon Distribution in Lambda CDM Galaxies
Cuspy No More: How Outflows Affect the Central Dark Matter and Baryon Distribution in Lambda CDM Galaxies
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DOI：
10.1111/j.1365-2966.2012.20696.x
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发表时间：
2012-02
期刊：
影响因子：
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通讯作者：
F. Governato;A. Zolotov;A. Pontzen;C. Christensen;S. Oh;A. Brooks;T. Quinn;S. Shen;J. W. U. O. Wa
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文献类型：
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作者：
F. Governato;A. Zolotov;A. Pontzen;C. Christensen;S. Oh;A. Brooks;T. Quinn;S. Shen;J. W. U. O. Wa
我们研究的内部暗物质（DM）的演化和重子密度分布的一个新的样本的模拟场星系使用完全宇宙学，λ CDM，高分辨率SPH + N体模拟。这些模拟包括显式氢和金属冷却，星星形成（SF）和超新星（SNe）驱动的气体外流。从高红移开始，爆发性SF之后的快速、重复的气体流出将能量转移到DM分量，并显着拉平了目前恒星质量在10^4.5 - 10^9.8 M太阳范围内的星系的原始“尖形”中心DM质量轮廓。在z=0时，我们星系DM密度分布的中心斜率（从它们的中心测量，在0.3到0.7千秒差距之间）与rhoDM propto r^alpha很好地拟合，α\simeq-0.5 + 0.35 log_10（Mstar/10^8 Msolar），其中Mstar是星系的恒星质量，4 < log_10 Mstar < 9.4。这些值意味着DM配置文件平坦比DM-只有模拟和推断的东西和小东西调查的星系中的密切一致。只有在非常小的晕，其中由z=0星星的形成转化成恒星的原始重子丰度小于~ 0.03%，流出不平坦的原始尖形DM轮廓的半径解决了我们的模拟。在每个模拟星系的内部500 pc范围内测量的质量（DM和重子）在恒星质量的四个数量级上几乎保持不变，M星为10^9 Msolar。这一发现与对微弱的本星系群矮星和场星系的估计是一致的。这些结果解决了CDM模型所面临的突出问题之一，即尖锐的DM配置文件和浅的中央DM分布在星系中观察到的原始预测之间的强烈差异。
We examine the evolution of the inner dark matter (DM) and baryonic density profile of a new sample of simulated field galaxies using fully cosmological, Lambda CDM, high resolution SPH + N-Body simulations. These simulations include explicit H2 and metal cooling, star formation (SF) and supernovae (SNe) driven gas outflows. Starting at high redshift, rapid, repeated gas outflows following bursty SF transfer energy to the DM component and significantly flatten the originally `cuspy' central DM mass profile of galaxies with present day stellar masses in the 10^4.5 -- 10^9.8 Msolar range. At z=0, the central slope of the DM density profile of our galaxies (measured between 0.3 and 0.7 kpc from their centre) is well fitted by rhoDM propto r^alpha with alpha \simeq -0.5 + 0.35 log_10(Mstar/10^8Msolar) where Mstar is the stellar mass of the galaxy and 4 < log_10 Mstar < 9.4. These values imply DM profiles flatter than those obtained in DM--only simulations and in close agreement with those inferred in galaxies from the THINGS and LITTLE THINGS survey. Only in very small halos, where by z=0 star formation has converted less than ~ 0.03% of the original baryon abundance into stars, outflows do not flatten the original cuspy DM profile out to radii resolved by our simulations. The mass (DM and baryonic) measured within the inner 500 pc of each simulated galaxy remains nearly constant over four orders of magnitudes in stellar mass for Mstar 10^9 Msolar. This finding is consistent with estimates for faint Local Group dwarfs and field galaxies. These results address one of the outstanding problems faced by the CDM model, namely the strong discrepancy between the original predictions of cuspy DM profiles and the shallower central DM distribution observed in galaxies.