STAR FORMATION IN THE EARLY UNIVERSE: BEYOND THE TIP OF THE ICEBERG-猫眼课题宝

DOI：

10.1088/0004-637x/754/1/46

发表时间：

2012-01

期刊：

The Astrophysical Journal

影响因子：

通讯作者：

中科院分区：

其他

文献类型：

作者：

N. Tanvir;A. Levan;A. Fruchter;J. Fynbo;J. Hjorth;K. Wiersema;M. Bremer;J. Rhoads;P. Jakobsson;P. O’Brien;E. Stanway;D. Bersier;P. Natarajan;P. Natarajan;J. Greiner;D. Watson;A. Castro‐Tirado;R. Wijers;R. Starling;K. Misra;J. Graham;C. Kouveliotou

我们提出了后期哈勃太空望远镜（HST）成像的领域，6雨燕伽玛射线暴（GRB）躺在5.0赫兹<$9.5。我们的数据包括非常深的观测领域的最遥远的光谱证实的爆发，GRB 090423，在z = 8.2。利用它们的余辉所提供的精确位置，我们可以对它们的宿主星系的光度进行严格的限制。在z = 5.11的GRB 060522的情况下，在GRB位置附近有一个边际过剩的通量，这可能是检测到JAB = 28.5的宿主。其他的恒星都没有被探测到，这意味着所有的宿主都位于它们各自红移的L* 以下，所有情况下的星星形成率（SFR）都是1.4兆兆年。事实上，将这五个场与WFC 3-IR数据叠加，我们得出每个星系的平均SFR <0.17百万年。这些结果支持的命题，即大部分的星星的形成，因此综合紫外光度，在高红移出现在星系的深场观测的检测限以下。作出合理的假设，伽玛射线暴率是成比例的紫外线光度在早期允许我们比较我们的限制与预期的基础上的星系光度函数（LF）来自哈勃超深场和其他深场。我们推断，一个LF，这是朝着更陡峭的暗端斜率（α）和降低特征光度（L*），如一些其他的研究建议，迅速演变与我们的观察是一致的，而一个非演变的LF形状被排除在90%的置信度。虽然现在还不可能做出更有力的声明，但在未来，随着更大的样本和对GRB产生所需条件的更全面了解，像这样的研究对于探索星星形成的性质，星系LF的形状以及早期宇宙中电离光子的供应具有巨大的潜力。

We present late-time Hubble Space Telescope (HST) imaging of the fields of six Swift gamma-ray bursts (GRBs) lying at 5.0 ≲ z ≲ 9.5. Our data include very deep observations of the field of the most distant spectroscopically confirmed burst, GRB 090423, at z = 8.2. Using the precise positions afforded by their afterglows, we can place stringent limits on the luminosities of their host galaxies. In one case, that of GRB 060522 at z = 5.11, there is a marginal excess of flux close to the GRB position which may be a detection of a host at a magnitude JAB ≈ 28.5. None of the others are significantly detected, meaning that all the hosts lie below L* at their respective redshifts, with star formation rates (SFRs) ≲ 4 M☉ yr−1 in all cases. Indeed, stacking the five fields with WFC3-IR data, we conclude a mean SFR <0.17 M☉ yr−1 per galaxy. These results support the proposition that the bulk of star formation, and hence integrated UV luminosity, at high redshifts arises in galaxies below the detection limits of deep-field observations. Making the reasonable assumption that GRB rate is proportional to UV luminosity at early times allows us to compare our limits with expectations based on galaxy luminosity functions (LFs) derived from the Hubble Ultra-Deep Field and other deep fields. We infer that an LF, which is evolving rapidly toward steeper faint-end slope (α) and decreasing characteristic luminosity (L*), as suggested by some other studies, is consistent with our observations, whereas a non-evolving LF shape is ruled out at ≳ 90% confidence. Although it is not yet possible to make stronger statements, in the future, with larger samples and a fuller understanding of the conditions required for GRB production, studies like this hold great potential for probing the nature of star formation, the shape of the galaxy LF, and the supply of ionizing photons in the early universe.

STAR FORMATION IN THE EARLY UNIVERSE: BEYOND THE TIP OF THE ICEBERG

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