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arXiv 0811.2041astro-ph
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z~5 Lyman Break星系的恒星星族

The Stellar Populations of Lyman Break Galaxies at z~5

Kiyoto Yabe, Kouji Ohta, Ikuru Iwata, Marcin Sawicki, Naoyuki Tamura, Masayuki Akiyama, Kentaro Aoki

摘要:

本文给出了在GOODS-N及其两侧场(GOODS-FF)中,z~5处的Lyman Break Galeries(LBG)的谱能量分布(SED)拟合分析结果。利用GOODS-N中公开提供的IRAC图像和GOODS-FF中的IRAC数据,我们构建了z~5处大样本(~100个)UV选择星系的静止框架UV到光学SED。比较所观察到的SED与模型SED与人口合成代码,我们得出了一个最适合的参数(恒星质量,年龄,颜色过剩,恒星形成率)为每个样本LBG。恒星质量的范围从10^8到10^11 M_sun,中值为4.1x10^9 M_sun。与z=2-3的LBG的比较表明,在相同的静止坐标系UV光度范围内,z~5的LBG的质量比z=2-3的LBG系统地小3-4倍。恒星形成年龄比z=2-3的LBG相对年轻。我们还将我们样本的结果与z=5-6星系的其他研究进行了比较。虽然它们的性质似乎有相似之处和不同之处,但我们无法得出其意义。我们还推导出我们的样本的恒星质量函数,通过校正的不完整性。虽然大质量端的数密度与半解析模型的理论预测相当,但低质量部分的数密度小于模型预测。通过将恒星质量函数向下积分到10^8 M_sun,计算出z~5处的恒星质量密度为(0.7-2.4)x10^7 M_sun Mpc^-3。z~5处的恒星质量密度主要受恒星质量函数的质量部分控制。与其他观测研究和模型预测结果相比,我们的样品的质量密度与恒星质量密度随时间增加的一般趋势一致。

英文摘要:

We present the results of Spectral Energy Distribution(SED) fitting analysis for Lyman Break Galaxies(LBGs) at z~5 in the GOODS-N and its flanking fields (the GOODS-FF). With the publicly available IRAC images in the GOODS-N and IRAC data in the GOODS-FF, we constructed the rest-frame UV to optical SEDs for a large sample (~100) of UV-selected galaxies at z~5. Comparing the observed SEDs with model SEDs generated with a population synthesis code, we derived a best-fit set of parameters (stellar mass, age, color excess, and star formation rate) for each of sample LBGs. The derived stellar masses range from 10^8 to 10^11M_sun with a median value of 4.1x10^9M_sun. The comparison with z=2-3 LBGs shows that the stellar masses of z~5 LBGs are systematically smaller by a factor of 3-4 than those of z=2-3 LBGs in a similar rest-frame UV luminosity range. The star formation ages are relatively younger than those of the z=2-3 LBGs. We also compared the results for our sample with other studies for the z=5-6 galaxies. Although there seem to be similarities and differences in the properties, we could not conclude its significance. We also derived a stellar mass function of our sample by correcting for incompletenesses. Although the number densities in the massive end are comparable to the theoretical predictions from semi-analytic models, the number densities in the low-mass part are smaller than the model predictions. By integrating the stellar mass function down to 10^8 M_sun, the stellar mass density at z~5 is calculated to be (0.7-2.4)x10^7M_sun Mpc^-3. The stellar mass density at z~5 is dominated by massive part of the stellar mass function. Compared with other observational studies and the model predictions, the mass density of our sample is consistent with general trend of the increase of the stellar mass density with time.

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