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arXiv 1407.2263astro-ph.GA
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下一代室女星系团巡天。V.使用量身定制方法对M87的动态进行建模

The Next Generation Virgo cluster Survey. V. modelling the dynamics of M87 with the Made-to-Measure method

Ling Zhu, R. J. Long, Shude Mao, Eric W. Peng, Chengze Liu, Nelson Caldwell, Biao Li, John P. Blakeslee, Patrick Cote, Jean-Charles Cuillandre, Patrick Durrell,… 展开作者

Ling Zhu, R. J. Long, Shude Mao, Eric W. Peng, Chengze Liu, Nelson Caldwell, Biao Li, John P. Blakeslee, Patrick Cote, Jean-Charles Cuillandre, Patrick Durrell, Eric Emsellem, Laura Ferrarese, Stephen Gwyn, Andres Jordan, Ariane Lancon, Simona Mei, Roberto Munoz, Thomas Puzia

摘要:

用M2M方法研究了巨椭圆星系M87从中心到最外层的动力学过程。我们使用一个新的目录的922球状星团线的视线速度延伸到一个投影半径为180千秒差距(相当于25 M87有效半径),和SAURON积分场单位的数据在中央2.4千秒差距。新一代室女座巡天(NGVS)新观测到263个球状星团,主要位于40 kpc以上。在M2M模型中,引力势被看作是一个具有恒定恒星质光比的发光物质势和一个被建模为对数势的暗物质势的组合。我们的最佳动力学模型在I波段得到的恒星质光比为M/LI = 6.0(+ -0.3)M_sun/L_sun,暗物质的势标速度为591(+ -50)km/s,标度半径为42(+ -10)kpc。我们确定M87在180 kpc范围内的总质量为(1.5 ± 0.2)10^13 M_sun。40千秒差距内的质量小于先前使用球状星团运动学确定的不超过45千秒差距的估计。我们的新球状星团速度在更大的半径,我们看到,球状星团约40 kpc显示出一个非常大的速度色散,影响了以前的结果。我们推导出的质量是在很好的协议,从ROSAT X射线观测推断出180千秒差距。在30千秒差距内,我们的质量也与Chandra和XMM-Newton X射线观测推断的质量一致,而在120千秒差距内,它大约小20%。M87中球状星团的模型速度弥散各向异性β参数很小,从中心的-0.2变化到40 kpc的0.2,并逐渐减小到120 kpc的零。

英文摘要:

We study the dynamics of the giant elliptical galaxy M87 from the central to the outermost regions with the made-to-measure (M2M) method. We use a new catalogue of 922 globular cluster line-of- sight velocities extending to a projected radius of 180 kpc (equivalent to 25 M87 effective radii), and SAURON integral field unit data within the central 2.4 kpc. 263 globular clusters, mainly located beyond 40 kpc, are newly observed by the Next Generation Virgo Survey (NGVS). For the M2M modelling, the gravitational potential is taken as a combination of a luminous matter potential with a constant stellar mass-to-light ratio and a dark matter potential modelled as a logarithmic potential. Our best dynamical model returns a stellar mass-to-light ratio in the I band of M/LI = 6.0(+ -0.3) M_sun/L_sun with a dark matter potential scale velocity of 591(+ -50) km/s and scale radius of 42(+ -10) kpc. We determine the total mass of M87 within 180 kpc to be (1.5 + - 0.2) 10^13 M_sun. The mass within 40 kpc is smaller than previous estimates determined using globular cluster kinematics that did not extend beyond 45 kpc. With our new globular cluster velocities at much larger radii, we see that globular clusters around 40 kpc show an anomalously large velocity dispersion which affected previous results. The mass we derived is in good agreement with that inferred from ROSAT X-ray observation out to 180 kpc. Within 30 kpc our mass is also consistent with that inferred from Chandra and XMM-Newton X-ray observations, while within 120 kpc it is about 20% smaller. The model velocity dispersion anisotropy beta parameter for the globular clusters in M87 is small, varying from -0.2 at the centre to 0.2 at 40 kpc, and gradually decreasing to zero at 120 kpc.

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