A Census of Optical and Near-Infrared Selected Star-forming and Passively Evolving Galaxies at Redshift z ~ 2
A Census of Optical and Near-Infrared Selected Star-forming and Passively Evolving Galaxies at Redshift z ~ 2
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DOI：
10.1086/444588
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发表时间：
2005-07
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通讯作者：
N. Reddy;D. Erb;C. Steidel;A. Shapley;K. Adelberger;M. Pettini
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作者：
N. Reddy;D. Erb;C. Steidel;A. Shapley;K. Adelberger;M. Pettini
使用广泛的多波长数据在GOODS-North领域，包括我们的地面静止框架紫外光谱和近红外成像，我们构建和绘制的光学和近红外选择的恒星形成和被动演化的星系在红移1.4 <$z <$2.6的样本之间的比较。我们发现，在z ~ 2恒星形成星系的样本中，当受到共同的K波段限制时，它们的光学（UnG）和近红外（BzK）颜色选择在70%-80%的重叠。深钱德拉数据表明，在近红外选定的物体中，活动星系核的比例约为25%，其中大部分发生在近红外明亮物体（Ks 2.3星系，遥远的红色星系（DRG）作为Ks的函数非常相似，Ks为20.5。最红的DRG和（z - K）AB = 3的BzK星系没有X射线辐射，这表明它们必须有下降的星星形成历史来解释它们的红色和低SFR。虽然被动演化星系的M/L比平均而言可能更大，但斯皮策IRAC的数据表明，它们推断的恒星质量并没有超过光学选择星系的范围，这表明当前SFR的差异可能并不表明光学和近红外选择的大质量星系之间的根本差异（M* > 1011 M）。我们考虑光学，近红外，亚毫米选择星系的星星形成率密度（SFRD）在z ~ 2的贡献，考虑到样本重叠。UnG星系和BzK星系到Ks = 22和DRG星系到Ks = 21的1.4 × z × 2.6区间的SFRD约为0.10 ± 0.02 M yr-1 Mpc-3。光学选择的星系，以<$s = 25.5和Ks = 22.0占约70%的总数。在红移1.4 < z < 2.6的S850 μm ~ 4 mJy的射电选择亚毫米星系中，超过80%的星系满足BX/BM、BzK和DRG中的一个或多个判据。
Using the extensive multiwavelength data in the GOODS-North field, including our ground-based rest-frame UV spectroscopy and near-IR imaging, we construct and draw comparisons between samples of optical and near-IR selected star-forming and passively evolving galaxies at redshifts 1.4 ≲ z ≲ 2.6. We find overlap at the 70%-80% level in samples of z ~ 2 star-forming galaxies selected by their optical (UnGℛ) and near-IR (BzK) colors when subjected to common K-band limits. Deep Chandra data indicate a ~25% AGN fraction among near-IR selected objects, much of which occurs among near-IR bright objects (Ks 2.3 galaxies (i.e., distant red galaxies; DRGs) are very similar as a function of Ks, with Ks 20.5. The absence of X-ray emission from the reddest DRGs and BzK galaxies with (z - K)AB ≳ 3 indicates that they must have declining star formation histories to explain their red colors and low SFRs. While the M/L ratio of passively evolving galaxies may be larger on average, the Spitzer IRAC data indicate that their inferred stellar masses do not exceed the range spanned by optically selected galaxies, suggesting that the disparity in current SFR may not indicate a fundamental difference between optical and near-IR selected massive galaxies (M* > 1011 M☉). We consider the contribution of optical, near-IR, and submillimeter selected galaxies to the star formation rate density (SFRD) at z ~ 2, taking into account sample overlap. The SFRD in the interval 1.4 ≲ z ≲ 2.6 of UnGℛ and BzK galaxies to Ks = 22 and DRGs to Ks = 21 is ~0.10 ± 0.02 M☉ yr-1 Mpc-3. Optically selected galaxies to ℛ = 25.5 and Ks = 22.0 account for ~70% of this total. Greater than 80% of radio-selected submillimeter galaxies to S850 μm ~ 4 mJy with redshifts 1.4 < z < 2.6 satisfy either one or more of the BX/BM, BzK, and DRG criteria.