科研之友
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摘要
We have identified a very interesting Ly alpha emitter (LAE), whose Ly alpha emission line has an extremely large observed equivalent width of EW0 = 436(-149)(+422) angstrom, which corresponds to an extraordinarily large intrinsic rest-frame equivalent width of EW0int = 872(-298)(+844) angstrom after the average intergalactic absorption correction. The object was spectroscopically confirmed to be a real LAE by its apparent asymmetric Ly alpha line profile detected at z = 6.538. The continuum emission of the object was definitely detected in our deep z%26apos;-band image; thus, its EW0 was reliably determined. Follow-up deep near-infrared spectroscopy revealed emission lines of neither He II lambda 1640 as an apparent signature of Population III (Pop III) nor C IV lambda 1549 as proof of an active nucleus. No detection of the short-lived He II lambda 1640 line is not necessarily inconsistent with the interpretation that the underlying stellar population of the object is dominated by Pop III. We found that the observed extremely large EW0 of the Ly alpha emission and the upper limit on the EW0 of the He II lambda 1640 emission can be explained by population synthesis models favoring a very young age less than 2-4 Myr and massive metal-poor (Z %26lt; 10(-5)) or even metal-free stars. The observed large EW0 of Ly alpha is insufficiently explained by Population I/II synthesis models with Z %26gt;= 10(-3). However, we cannot conclusively rule out the possibility that this object is composed of a normal stellar population with a clumpy dust distribution, which could enhance the Ly alpha EW0, though its significance is still unclear.
- 出版日期2012-12-20
- 单位中国科学院国家天文台
