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首页> 外文期刊>The Astrophysical journal >THE STELLAR HALO IN THE LARGE MAGELLANIC CLOUD: MASS, LUMINOSITY, AND MICROLENSING PREDICTIONS
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THE STELLAR HALO IN THE LARGE MAGELLANIC CLOUD: MASS, LUMINOSITY, AND MICROLENSING PREDICTIONS

机译:大型麦哲伦星云中的恒星光晕:质量,亮度和微缩预测

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摘要

Recently obtained kinematic data have shown that the Large Magellanic Cloud (LMC) possesses an old stellar halo. In order to further characterize the properties of this halo, parametric King models are fitted to the surface density of RR Lyrae stars. Using data from both the MACHO and OGLE II microlensing surveys, the model fits yield the center of their distribution at α = 5~h21.1~m +- 0.8~m, δ = -69°45′ +- 6′ (J2000.0) and a core radius of 1.42 +- 0.12 kpc. As a check, the halo model is compared with RR Lyrae star counts in fields near the LMC's periphery previously surveyed with photographic plates. These data, however, require a cautious interpretation. Several topics regarding the LMC stellar halo are discussed. First, the properties of the halo imply a global mass-to-light ratio of M/L_V = 5.3 +- 2.1 and a total mass of (1.6 +- 0.6) x 10~(10) solar mass for the LMC, in good agreement with estimates based on the rotation curve. Second, although the LMC's disk and halo are kinematically distinct, the shape of the surface density profile of the halo is remarkably similar to that of the young disk. For example, the best-fit exponential scale length for the RR Lyrae stars is 1.47 +- 0.08 kpc, which compares to 1.46 kpc for the LMC's blue light. In the Galaxy, the halo and disk do not resemble each other like this. Finally, a local maximum in the LMC's microlensing optical depth due to halo-on-disk stellar self-lensing is predicted. For the parameters of the stellar halo obtained, this maximum is located near MACHO events LMC-4 and LMC-23 and is large enough to possibly account for these two events but not for all of the observed microlensing.
机译:最近获得的运动学数据表明,大麦哲伦星云(LMC)具有旧的恒星晕。为了进一步表征该晕的性质,将参数King模型拟合到RR天琴星的表面密度。使用来自MACHO和OGLE II微透镜测量的数据,该模型拟合得出它们的分布中心为α= 5〜h21.1〜m +-0.8〜m,δ= -69°45'+-6'(J2000 .0)和1.42±0.12 kpc的芯半径。作为检验,将光晕模型与LM Lyrae恒星计数进行比较,该恒星计数是在LMC外围附近的田野中进行过以前的照相制版测量。但是,这些数据需要谨慎的解释。讨论了有关LMC恒星晕的几个主题。首先,光晕的性质意味着LMC的整体质量与光之比为M / L_V = 5.3 +-2.1,总质量为(1.6 +-0.6)x 10〜(10)太阳质量。与基于旋转曲线的估计值一致。其次,尽管LMC的圆盘和光晕在运动学上是不同的,但是光晕的表面密度轮廓的形状与年轻圆盘的表面密度轮廓非常相似。例如,RR天琴星的最适合指数尺度长度为1.47±-0.08 kpc,而LMC的蓝光为1.46 kpc。在银河系中,光环和磁盘并不像这样。最后,可以预测出由于光晕在磁盘上恒星自透镜而引起的LMC微透镜光学深度的局部最大值。对于所获得的恒星晕的参数,该最大值位于MACHO事件LMC-4和LMC-23附近,并且足够大以可能解释这两个事件,但不能解释所有观察到的微透镜。

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