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arXiv 1004.5247astro-ph.GAastro-ph.CO
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朝向麦哲伦云的微透镜的OGLE视图。II。OGLE-II SMC数据

The OGLE View of Microlensing towards the Magellanic Clouds. II. OGLE-II SMC data

L. Wyrzykowski, S. Kozlowski, J. Skowron, V. Belokurov, M. C. Smith, A. Udalski, M. K. Szymanski, M. Kubiak, G. Pietrzynski, I. Soszynski, O. Szewczyk

摘要:

本文的主要目的是提供证据,可以证明或证伪的假设,即暗物质在星系晕可以聚集成恒星质量的紧凑的对象。如果这样的物体存在,它们将作为麦哲伦云外部光源的透镜,产生可观察到的微透镜效应。我们目前的结果,我们搜索这样的事件,从第二阶段的OGLE调查(1996-2000年)对SMC的数据的基础上。我们使用的数据集由分布在2.4平方度区域内的210万个监测源组成。我们只发现了一个微透镜事件的候选者,但是其质量差的光变曲线限制了我们对到透镜物体的确切距离的讨论。给定单个事件,考虑到探测效率模拟的混合(恒星拥挤),并推导出HST校正的监测恒星数量,微透镜光学深度为tau=(1.55+-1.55 10 e-7。这一结果与预期的SMC自透镜信号一致,无需引入暗物质微透镜。拒绝这个不可信的事件导致了以MACHO形式存在的暗物质的比例上限,对于质量在0.4 Msun左右的偏转器,f<20%,对于质量在0.003和0.2 Msun之间的偏转器,f<11%(95%的置信限)。我们的研究结果表明,银河系的暗物质不太可能是聚集的,也不可能形成亚太阳质量范围内的致密物体。

英文摘要:

The primary goal of this paper is to provide the evidence that can either prove or falsify the hypothesis that dark matter in the Galactic halo can clump into stellar-mass compact objects. If such objects existed, they would act as lenses to external sources in the Magellanic Clouds, giving rise to an observable effect of microlensing. We present the results of our search for such events, based on the data from the second phase of the OGLE survey (1996-2000) towards the SMC. The data set we used is comprised of 2.1 million monitored sources distributed over an area of 2.4 square degrees. We found only one microlensing event candidate, however its poor quality light curve limited our discussion on the exact distance to the lensing object. Given a single event, taking the blending (crowding of stars) into account for the detection efficiency simulations, and deriving the HST-corrected number of monitored stars, the microlensing optical depth is tau=(1.55+-1.55)10e-7. This result is consistent with the expected SMC self-lensing signal, with no need of introducing dark matter microlenses. Rejecting the unconvincing event leads to the upper limit on the fraction of dark matter in the form of MACHOs to f<20 per cent for deflectors' masses around 0.4 Msun and f<11 per cent for masses between 0.003 and 0.2 Msun (95 per cent confidence limit). Our result indicates that the Milky Way's dark matter is unlikely to be clumpy and form compact objects in the sub-solar-mass range.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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