The z = 0.0912 and z = 0.2212 Damped Lyα Galaxies along the Sight Line toward the Quasar OI 363
The z = 0.0912 and z = 0.2212 Damped Lyα Galaxies along the Sight Line toward the Quasar OI 363
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z = 0.0912 和 z = 0.2212 阻尼 Lyα 星系沿着类星体 OI 363 的视线
DOI：
10.1086/320660
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
A. Smette
中科院分区：
文献类型：
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作者：
D. Turnshek;S. Rao;D. Nestor;W. Lane;E. Monier;J. Bergeron;A. Smette
新的光学和红外观测沿着瞄准线对类星体OI 363（0738+313）提出和讨论。排除选择性观测到的类星体，因为它们已知位于富含气体的星系和系统后面，而这些星系和系统缺乏实际Lyα线的紫外光谱观测，这条视线目前包含了在调查模式下发现的两个最低红移的经典阻尼Lyα (DLA)类星体吸收线系统（即N≥2 × 1020原子cm-2），一个在zabs = 0.0912，另一个在zabs = 0.2212。我们的新观测结果提出了这些吸收线系统对应的DLA星系的识别。z = 0.09的DLA星系似乎是一个延伸的低表面亮度星系，只有在红外图像中才能很容易地看到，并且可能显示出丰富的形态结构。假设没有类星体宿主星系的贡献，我们对LK≤0.13L的z = 0.09 DLA星系（对于H0 = 65 km s-1 Mpc-1， Ω = 1， Λ = 0的宇宙学）的k波段光度设置了上限。更实际地说，类星体核和宿主光相减得到LK≈0.08L。星系和类星体视线之间的撞击参数非常小，b < 3.6 kpc（< 2”），这使得测量变得困难。z = 0.22的DLA星系是一颗撞击参数b = 20 kpc时k波段光度为LK≈0.1L的早型矮星。它的颜色是中性的，与恒星形成模型一致，表明它的形成时间不到几个Gyr（即zf≈0.3-0.9）。因此，可以想象，它的祖先起源于中等红移的“暗淡蓝色星系”群。总的来说，这些结果支持了越来越多的证据，即DLA星系是从各种富含气体的星系类型中提取出来的。
New optical and infrared observations along the sight line toward the quasar OI 363 (0738+313) are presented and discussed. Excluding quasars selectively observed because they were known to be located behind gas-rich galaxies and systems which lack confirming UV spectroscopic observations of the actual Lyα line, this sight line presently contains the two lowest redshift classical damped Lyα (DLA) quasar absorption-line systems found in survey mode (i.e., with N ≥ 2 × 1020 atoms cm-2), one at zabs = 0.0912 and the other at zabs = 0.2212. Our new observations suggest identifications for the DLA galaxy counterparts of these absorption-line systems. The z = 0.09 DLA galaxy appears to be an extended low surface brightness galaxy which is easily visible only in infrared images and shows possible rich morphological structure. Assuming there is no contribution from the quasar host galaxy, we place an upper limit on the K-band luminosity of the z = 0.09 DLA galaxy of LK ≤ 0.13L (for a cosmology with H0 = 65 km s-1 Mpc-1, Ω = 1, and Λ = 0). More realistically, a subtraction of the quasar nuclear and host light yields LK ≈ 0.08L. The impact parameter between the galaxy and quasar sight line is very small, b < 3.6 kpc (< 2''), which makes measurements difficult. The z = 0.22 DLA galaxy is an early-type dwarf with a K-band luminosity of LK≈ 0.1L at impact parameter b = 20 kpc. Its colors are neutral and consistent with star formation models, suggesting its formation epoch was less than a few Gyr ago (i.e., zf ≈ 0.3-0.9). Thus, it is conceivable that its progenitor originated from the population of "faint blue galaxies" seen at moderate redshifts. In general, these results serve to support mounting evidence that DLA galaxies are drawn from a wide variety of gas-rich galaxy types.