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arXiv 1602.02753astro-ph.GA
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用星系尺度强透镜探测低质量星系团成员的暗物质分数

Dark matter fraction of low-mass cluster members probed by galaxy-scale strong lensing

W. G. Parry, C. Grillo, A. Mercurio, I. Balestra, P. Rosati, L. Christensen, M. Lombardi, G. B. Caminha, M. Nonino, A. M. Koekemoer, K. Umetsu

摘要:

我们提出了一个强透镜系统,由一个z = 2.387的源的4个多重图像组成,该源由两个透镜星系G1和G2产生,属于星系团MACS J1115.9+0129,z = 0.353。我们使用的意见采取的一部分,与哈勃望远镜,CLASH,其光谱的后续计划在甚大望远镜,CLASH-VLT的集群透镜和超新星调查,估计总质量分布的两个星系和集群通过强引力透镜模型。我们发现两个透镜星系在半光半径R_{e}内的总投影质量值分别为:M_{T,G1}(< R_{e,G1})=(3.6 +/- 0.4)x 10^{10} M_{Sun}和M_{T,G2}(< R_{e,G2})=(4.2 +/- 1.6)x 10^{10} M_{Sun}。G1和G2的有效速度频散值分别为(122 +/- 7)km/s和(137 +/- 27)km/s。我们注意到,这些值是相对较低的相比,~200-300公里/秒,典型的透镜星系中发现的领域由以前的调查。通过拟合G1和G2的光谱能量分布,我们测量了在R_{e}内的总质量分数上的投影发光,G1为0.11 +/- 0.03,G2为0.73 +/- 0.32。质量较小的星系G1内部区域暗物质占主导地位,这一事实提出了一个问题,即早期星系核心的暗物质比例是否取决于它们的质量。对强透镜系统的进一步研究将有助于我们理解暗物质对星系内部结构和演化的影响。

英文摘要:

We present a strong lensing system, composed of 4 multiple images of a source at z = 2.387, created by two lens galaxies, G1 and G2, belonging to the galaxy cluster MACS J1115.9+0129 at z = 0.353. We use observations taken as part of the Cluster Lensing and Supernova survey with Hubble, CLASH, and its spectroscopic follow-up programme at the Very Large Telescope, CLASH-VLT, to estimate the total mass distributions of the two galaxies and the cluster through strong gravitational lensing models. We find that the total projected mass values within the half-light radii, R_{e}, of the two lens galaxies are M_{T,G1}(< R_{e,G1}) = (3.6 +/- 0.4) x 10^{10}M_{Sun} and M_{T,G2}(< R_{e,G2}) = (4.2 +/- 1.6) x 10^{10}M_{Sun}. The effective velocity dispersion values of G1 and G2 are (122 +/- 7) km/s and (137 +/- 27) km/s, respectively. We remark that these values are relatively low when compared to those of ~200-300 km/s, typical of lens galaxies found in the field by previous surveys. By fitting the spectral energy distributions of G1 and G2, we measure projected luminous over total mass fractions within R_{e} of 0.11 +/- 0.03, for G1, and 0.73 +/- 0.32, for G2. The fact that the less massive galaxy, G1, is dark-matter dominated in its inner regions raises the question of whether the dark matter fraction in the core of early-type galaxies depends on their mass. Further investigating strong lensing systems will help us understand the influence that dark matter has on the structure and evolution of the inner regions of galaxies.

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