The Density of Lyα Emitters at Very High Redshift
The Density of Lyα Emitters at Very High Redshift
复制标题
极高红移处 Lyα 发射体的密度
DOI：
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
R. McMahon
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文献类型：
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作者：
E. Hu;L. Cowie;R. McMahon
我们描述了窄带和光谱搜索发射线恒星形成星系的红移范围3-6与10米凯克II望远镜。这些搜索产生了大量只有一条强（EW 100流明）发射线的天体，位于4000-8500流明范围内。在λ~5390和λ ~6741的窄带样品中发现的天体光谱表明，这些非常高的等效宽度发射线通常在z~3.4和4.5处红移Lyα 1216。在5 σ探测极限1.5×10−17尔格cm-2 s-1以上，这些发射体的密度在z~3.4和4.5时大约为每单位z 15，000 deg-2。一个互补的更深（1 σ~10−18 ergs cm-2 s-1）的狭缝光谱搜索覆盖了一个宽的红移范围，但空间区域更有限（200 arcsec 2），显示这样的物体可以在红移范围z=3-6内被发现，目前最高的红移是在z=5.64。Lyα通量分布可以用来估计在没有红化的情况下最小星星形成率大约为0.01 M Tmpc-3 yr-1（H 0 =65 km s-1 Mpc-1，q 0 =0.5）。由于观测到的等效宽度接近大质量星星电离的最大值，因此对红化的修正可能不会大于2倍。在仍然很大的不确定性范围内，Lyα选择样本的星星形成率与z~3处的色裂选择样本相当，但在更高的红移处，可能代表总速率的增加部分。这种较高的z人口可以很容易地用大型地面望远镜进行研究。
We describe narrowband and spectroscopic searches for emission-line star-forming galaxies in the redshift range 3-6 with the 10 m Keck II Telescope. These searches yield a substantial population of objects with only a single strong (EW ≫100 Å) emission line, lying in the 4000-8500 Å range. Spectra of the objects found in narrowband-selected samples at λ~5390 and ~6741 Å show that these very high equivalent width emission lines are generally redshifted Lyα 1216 Å at z~3.4 and 4.5. The density of these emitters above the 5 σ detection limit of 1.5×10−17 ergs cm-2 s-1 is roughly 15,000 deg-2 per unit z at both z~3.4 and 4.5. A complementary deeper (1 σ~10−18 ergs cm-2 s-1) slit spectroscopic search covering a wide redshift range but a more limited spatial area (200 arcsec2) shows that such objects can be found over the redshift range z=3-6, with the currently highest redshift detected being at z=5.64. The Lyα flux distribution can be used to estimate a minimum star formation rate in the absence of reddening of roughly 0.01 M☉ Mpc-3 yr-1 (H0=65 km s-1 Mpc-1, q0=0.5). Corrections for reddening are likely to be no larger than a factor of 2, since observed equivalent widths are close to the maximum values obtainable from ionization by a massive star population. Within the still significant uncertainties, the star formation rate from the Lyα-selected sample is comparable to that of the color-break-selected samples at z~3 but may represent an increasing fraction of the total rates at higher redshifts. This higher z population can be readily studied with large ground-based telescopes.