大半径模拟的大质量早型星系的质量和angular momentum分布
The mass and angular momentum distribution of simulated massive early-type galaxies to large radii
摘要：
我们研究的黑暗和明亮的质量分布，圆速度曲线（CVC），视线运动学，和角动量的样本的42个宇宙学变焦模拟的大质量星系。使用时间平滑技术，我们能够达到大半径。我们发现：（i）几千秒差距以外的暗物质晕密度分布遵循简单的幂律模型，低质量系统的暗物质CVC是平坦的，高质量晕的CVC是上升的。在大半径处的投影恒星密度分布可以用n>10的Sersic函数拟合，比典型的ETG大。（ii）大质量系统在大半径处的总CVC几乎是平的，而质量较小的系统的CVC略有减少。在大半径处的CVC的斜率与v_circ本身相关。（iii）Re内的暗物质分数在15-30%之间，在5 Re时增加到40-65%。更大更重的星系有更高的暗物质分数。（iv）模拟星系的短轴和它们的宿主暗物质晕是很好地对准的，它们的短轴与长轴的比率是相关的。（v）恒星vrms（R）剖面正在缓慢下降，这与大多数ETG外晕中的行星状星云观测结果一致。（vi）视线速度场v表明，小半径和大半径处的旋转特性是相关的。累积比角动量参数λ（R）的径向分布在2 ~ 5 Re范围内基本上是平的或略有上升，其值在[0.06，0.75]。（vii）恒星质量、5 Re下的椭圆率和λ（5 Re）是相关的：质量越大的系统，角动量越小，越圆，就像观测到的ETG一样。（viii）更大质量的星系与大部分的吸积星有径向各向异性的速度分布外Re。切向各向异性只出现在原位恒星比例高的星系中。(Full PDF格式的摘要）
英文摘要：
We study the dark and luminous mass distributions, circular velocity curves (CVC), line-of-sight kinematics, and angular momenta for a sample of 42 cosmological zoom simulations of massive galaxies. Using a temporal smoothing technique, we are able to reach large radii. We find that: (i)The dark matter halo density profiles outside a few kpc follow simple power-law models, with flat dark matter CVCs for lower-mass systems, and rising CVCs for high-mass haloes. The projected stellar density distributions at large radii can be fitted by Sersic functions with n>10, larger than for typical ETGs. (ii)The massive systems have nearly flat total CVCs at large radii, while the less massive systems have mildly decreasing CVCs. The slope of the CVC at large radii correlates with v_circ itself. (iii)The dark matter fractions within Re are in the range 15-30% and increase to 40-65% at 5Re. Larger and more massive galaxies have higher dark matter fractions. (iv)The short axes of simulated galaxies and their host dark matter haloes are well aligned and their short-to-long axis ratios are correlated. (v)The stellar vrms(R) profiles are slowly declining, in agreement with planetary nebulae observations in the outer haloes of most ETGs. (vi)The line-of-sight velocity fields v show that rotation properties at small and large radii are correlated. Most radial profiles for the cumulative specific angular momentum parameter lambda(R) are nearly flat or slightly rising, with values in [0.06,0.75] from 2Re to 5Re. (vii)Stellar mass, ellipticity at 5Re, and lambda(5Re) are correlated: the more massive systems have less angular momentum and are rounder, as for observed ETGs. (viii)More massive galaxies with a large fraction of accreted stars have radially anisotropic velocity distributions outside Re. Tangential anisotropy is seen only for galaxies with high fraction of in-situ stars. (Full abstract in PDF)
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