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arXiv 1101.2291astro-ph.CO
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引力透镜对甚高红移星系数计数的畸变

A distortion of very--high--redshift galaxy number counts by gravitational lensing

J. Stuart B. Wyithe, Haojing Yan, Rogier A. Windhorst, Shude Mao

摘要:

观测到的高红移星系候选者的计数已经被用来建立一个统计描述的恒星形成活动在红移z >~ 7,当星系再电离宇宙。标准模型预测,引力透镜的高发生率可能会扭曲这些最早星系的流量和数量的测量。据估计,这种情况发生的原始概率约为0.5%,但由于观测偏差,可能会更大。在这里,我们报告说,引力透镜很可能占主导地位的观测性质的星系的红移z >~ 12,当仪器的极限星等预计将比星系样本的特征星等。数量计数可以修改一个数量级,大多数星系是多重成像系统的一部分,距离z ~ 2处较亮的前景星系不到1弧秒。这种由透镜引起的高红移星系和前景星系的关联,可能已经在z ~ 10.6的候选星系样本中观察到了。未来的巡天观测需要考虑高红移星系样本中显著的引力透镜偏差。

英文摘要:

The observed number counts of high-redshift galaxy candidates have been used to build up a statistical description of star-forming activity at redshift z >~ 7, when galaxies reionized the Universe. Standard models predict that a high incidence of gravitational lensing will probably distort measurements of flux and number of these earliest galaxies. The raw probability of this happening has been estimated to be ~ 0.5 percent, but can be larger owing to observational biases. Here we report that gravitational lensing is likely to dominate the observed properties of galaxies with redshifts of z >~ 12, when the instrumental limiting magnitude is expected to be brighter than the characteristic magnitude of the galaxy sample. The number counts could be modified by an order of magnitude, with most galaxies being part of multiply imaged systems, located less than 1 arcsec from brighter foreground galaxies at z ~ 2. This lens-induced association of high-redshift and foreground galaxies has perhaps already been observed among a sample of galaxy candidates identified at z ~ 10.6. Future surveys will need to be designed to account for a significant gravitational lensing bias in high-redshift galaxy samples.

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