Lyman Limit Imaging of High Redshift Galaxies. III. New Observations of 4 QSO Fields
Lyman Limit Imaging of High Redshift Galaxies. III. New Observations of 4 QSO Fields
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DOI：
10.1086/117709
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发表时间：
1995-09
期刊：
影响因子：
--
通讯作者：
C. Steidel;M. Pettini;D. Hamilton
中科院分区：
文献类型：
--
作者：
C. Steidel;M. Pettini;D. Hamilton
我们给出了四个新领域的深度莱曼极限成像的结果，作为继续寻找价格为3.0美元的星系的一部分。该技术使用定制的宽带滤光片集($U_n G{\cal R}$)，旨在隔离具有叠加在其他平坦光谱紫外线连续带上的莱曼连续带的物体。这些观测的具体目的是探测产生光学厚度类星体金属线吸收系统的已知星系，但对红移处更广泛分布的天体同样敏感。结合之前发表的调查结果，我们现在已经在距离类星体视线3~弧秒的范围内，在6种情况中发现了2种具有预期的恒星形成星系性质的天体；两个候选吸收体具有相似的光度，$M_B\simeq-22$($Q_0=0.5$，$H_0=50$\kms MPC$^{-1}$)，以及碰撞参数$R\sim 10~h^{-1}$~kpc。强健的Lyman Break天体的平均表面密度为每平方角分钟0.5个星系，直到星等极限${\cal R}=25.0$。一个基于正常星系性质的简单的“不演化”模型预测，莱曼破裂天体的密度只比观测到的大几倍。我们的结论是，在$z=3-3.5美元的位置上，已经有相当数量的恒星形成星系，具有相对正常的光度。
We present the results of deep Lyman limit imaging in four new fields as part of a continuing search for galaxies at $3.0 \le z \le 3.5$. The technique uses a custom broad--band filter set ($U_n G {\cal R}$) designed to isolate objects having Lyman continuum breaks superposed on otherwise flat--spectrum ultraviolet continua. The observations are specifically aimed at detecting known galaxies producing optically thick QSO metal line absorption systems, but are equally sensitive to more generally distributed objects at the redshifts of interest. Together with previously published results of the survey, we have now detected in two out of six cases objects with the expected properties of star--forming galaxies at $z \simgt 3$ within 3~arcsec of the QSO sight lines; the two candidate absorbers have similar luminosities, $M_B \simeq -22$ ($q_0=0.5$, $H_0=50$ \kms Mpc$^{-1}$), and impact parameters, $R \sim 10~h^{-1}$~kpc. The average surface density of robust Lyman break objects is $\sim 0.5$ galaxies per square arcminute to a magnitude limit ${\cal R} = 25.0$. A simple, ``no evolution'' model based on the properties of normal galaxies at $z \simlt 1$ predicts a density of Lyman break objects only a few times larger than observed. We conclude that there is a substantial population of star--forming galaxies, of relatively normal luminosity, already in place at $z = 3 - 3.5$.