Keck Deep Fields. II. The Ultraviolet Galaxy Luminosity Function at z ~ 4, 3, and 2
Keck Deep Fields. II. The Ultraviolet Galaxy Luminosity Function at z ~ 4, 3, and 2
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凯克深田。
DOI：
10.1086/500999
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
D. Thompson
中科院分区：
文献类型：
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作者：
M. Sawicki;D. Thompson
我们使用非常深的UnG I多场成像在凯克望远镜获得的研究宇宙加倍其年龄从z ~ 4到~2的其余帧1700星系光度函数的演变。我们使用与Steidel团队使用的完全相同的过滤器和颜色-颜色选择，但探测明显较暗的极限，远低于L*。我们的成像深度使我们能够限制光度函数的暗端，在z ~ 3处达到M1700 ~ -18.5（相当于~1 M年），解释了星系数量和宇宙方差的N1/2不确定性。在得出以下结论之前，我们仔细研究了LF测量中系统偏差的许多潜在来源。我们发现莱曼破裂星系的光度函数随时间演化，并且这种演化与光度是微分的。结果最好限制在z ~ 4和z ~3的时期之间，在那里我们发现sub-L* 星系的数量密度随时间增加至少2.3倍（11 σ统计置信度）;当LF的暗端演变时，亮端似乎几乎保持不变，表明可能存在差异，亮度相关的演变（98.5%的统计概率）。潜在的系统偏差限制了我们得出关于光度函数继续演化到较低红移z ~ 2.2和z ~1.7的有力结论的能力，但是，尽管如此，我们研究的所有光度下z ~ 2.2星系的数密度（-22 > M1700 >-18）至少与z ~ 3星系的数密度一样高。虽然目前还不清楚观察到的演化机制是什么，但这种演化与光度不同的事实为提高我们对星系如何在高红移下形成和演化的理解开辟了新途径。
We use very deep UnGℛI multifield imaging obtained at the Keck telescope to study the evolution of the rest-frame 1700 Å galaxy luminosity function as the universe doubles its age from z ~ 4 to ~2. We use exactly the same filters and color-color selection as those used by the Steidel team but probe significantly fainter limits, well below L*. The depth of our imaging allows us to constrain the faint end of the luminosity function, reaching M1700 ~ -18.5 at z ~ 3 (equivalent to ~1 M☉ yr-1), accounting for both N1/2 uncertainty in the number of galaxies and cosmic variance. We carefully examine many potential sources of systematic bias in our LF measurements before drawing the following conclusions. We find that the luminosity function of Lyman break galaxies evolves with time and that this evolution is differential with luminosity. The result is best constrained between the epochs at z ~ 4 and ~3, where we find that the number density of sub-L* galaxies increases with time by at least a factor of 2.3 (11 σ statistical confidence); while the faint end of the LF evolves, the bright end appears to remain virtually unchanged, indicating that there may be differential, luminosity-dependent evolution (98.5% statistical probability). Potential systematic biases restrict our ability to draw strong conclusions about continued evolution of the luminosity function to lower redshifts, z ~ 2.2 and ~1.7, but, nevertheless, it appears certain that the number density of z ~ 2.2 galaxies at all luminosities we studied, -22 > M1700 > -18, is at least as high as that of their counterparts at z ~ 3. While it is not yet clear what mechanism underlies the observed evolution, the fact that this evolution is differential with luminosity opens up new avenues of improving our understanding of how galaxies form and evolve at high redshift.