利用弱引力透镜分析紧群
Compact Groups analysis using weak gravitational lensing
摘要：
我们提出了一个弱透镜分析的SDSS紧群（CG）的样本。使用测得的径向密度对比度分布，我们推导出平均质量的假设下，球对称，获得速度色散的奇异等温球模型，$σ_V = 270 \pm 40 \rm ~km~s^{-1}$，和NFW模型，$R_{200}=0.53\pm0.10\,h_{70}^{-1}\,\rm Mpc$。我们测试了三种不同的定义的CG中心，以确定最好的痕迹真正的暗物质晕中心，得出的结论是光度加权中心是最合适的选择。我们还研究了透镜信号对CG物理半径，组表面亮度和形态混合的依赖性。我们发现，更集中的星系成员的群体表现出更陡峭的质量分布和更大的速度色散。我们认为，这两个，一个可能的较低比例的闯入者和一个真正的陡峭的轮廓，可能在这种影响中发挥作用。直接的速度色散估计从成员光谱产生$σ_V \approx 230 \rm ~km~s^{-1}$与我们的透镜结果一致。
英文摘要：
We present a weak lensing analysis of a sample of SDSS Compact Groups (CGs). Using the measured radial density contrast profile, we derive the average masses under the assumption of spherical symmetry, obtaining a velocity dispersion for the Singular Isothermal Spherical model, $σ_V = 270 \pm 40 \rm ~km~s^{-1}$, and for the NFW model, $R_{200}=0.53\pm0.10\,h_{70}^{-1}\,\rm Mpc$. We test three different definitions of CGs centres to identify which best traces the true dark matter halo centre, concluding that a luminosity weighted centre is the most suitable choice. We also study the lensing signal dependence on CGs physical radius, group surface brightness, and morphological mixing. We find that groups with more concentrated galaxy members show steeper mass profiles and larger velocity dispersions. We argue that both, a possible lower fraction of interloper and a true steeper profile, could be playing a role in this effect. Straightforward velocity dispersion estimates from member spectroscopy yields $σ_V \approx 230 \rm ~km~s^{-1}$ in agreement with our lensing results.
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