利用弱重力透鏡效應探測星系團暗物質暈的橢圓率

Testing LCDM Predictions for the Dark-Matter Halo Asphericity Using Cluster Weak Lensing

譚雪瑩(Sut-Ieng Tam)

指導教授 ： 闕志鴻

共同指導教授 ： 梅津敬一(Keiichi Umetsu)

國立臺灣大學/理學院/物理學研究所/碩士(2016年)

https://doi.org/10.6342/NTU201601915

摘要

無資料

關鍵字

宇宙學 ； 星系團 ； 弱重力透鏡

並列摘要

Cosmological N-body simulations of Λ cold dark matter (ΛCDM) predicted the shape of DM halos to be triaxial, reflecting the collisionless nature of DM, and to be elongated in the preferential infall direction of materials. The predicted halo ellipticity is about 0.4(Jing & Suto (2002) [16]). Here we test this well-defined pre- dictions of the standard ΛCDM paradigm using wide-field weak shear lensing data of Umetsu et al.(2016) [41] obtained for a sample of 16 galaxy clusters targeted in the CLASH survey. We examine the mean halo ellipticity (projected halo aspheric- ity) in our cluster sample by measuring the quadrupole weak-lensing signal for each cluster, following the method of Clampitt & Jain(2015) [7]. First we assume the DM halos align with the BCGs. Our best-fit value for the ellipticity of an ensemble of CLASH clusters in this measurement is 0.26±0.07 corresponding to axis-ratio of 0.73±0.07. We also use the position angle of X-ray gas, assuming the dark matter halos align with the X-ray gas halo. In this measurement, we get the mean ellip- ticity is 0.29 ± 0.09 corresponding to axis-ratio of 0.71±0.10. The different between there two measurement is not significant but this give us a hint that the DM halo may be more likely align with X-ray gas. We will also discuss the estimates of the misalignment between central galaxies and halos from simulations and apply this correction to our result.

並列關鍵字

cosmology ； galaxy cluster ； weak gravitataional lensing

參考文獻

[14] T. Hamana, S. Miyazaki, K. Shimasaku, H. Furusawa, M. Doi, M. Hamabe, K. Imi, M. Kimura, Y. Komiyama, F. Nakata, N. Okada, S. Okamura, M. Ouchi, M. Sekiguchi, M. Yagi, and N. Yasuda. Cosmic Shear Statistics in the Suprime-Cam 2.1 Square Degree Field: Constraints on Ωm and σ8. ApJ, 597:98–110, Nov. 2003.

[1] S. Adhikari, C. Y. R. Chue, and N. Dalal. Three-point galaxy-galaxy lensing as a probe of dark matter halo shapes. J. Cosmology Astropart. Phys., 1:009, Jan. 2015.

[2] J. Bailin, C. Power, P. Norberg, D. Zaritsky, and B. K. Gibson. The anisotropic distribution of satellite galaxies. MNRAS, 390:1133–1156, Nov. 2008.

[3] J. Bailin and M. Steinmetz. Internal and External Alignment of the Shapes and Angular Momenta of ΛCDM Halos. ApJ, 627:647–665, July 2005.

[4] J. D. Barrow, S. P. Bhavsar, and D. H. Sonoda. A bootstrap resampling analysis of galaxy clustering. MNRAS, 210:19P–23P, Sept. 1984.