Toward an Understanding of the Rapid Decline of the Cosmic Star Formation Rate
Toward an Understanding of the Rapid Decline of the Cosmic Star Formation Rate
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DOI：
10.1086/429552
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发表时间：
2005-02
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影响因子：
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通讯作者：
E. Bell;C. Papovich;C. Wolf;E. Floc’h;J. Caldwell;M. Barden;E. Egami;D. H. Mcintosh;K. Meise
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文献类型：
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作者：
E. Bell;C. Papovich;C. Wolf;E. Floc’h;J. Caldwell;M. Barden;E. Egami;D. H. Mcintosh;K. Meise
本文首次分析了斯皮策空间望远镜对近1500个星系在0.65 ≤ z < 0.75的红移薄片中的深24 μm观测。我们结合联合收割机的红外数据与红移，静止帧光度，颜色从COMBO-17和形态从哈勃太空望远镜图像收集的星系形态和SED（GEMS）和大天文台起源深调查（GOODS）项目。为了描述自z ~ 0.7以来星星形成率（SFR）的下降，我们估计了该样本中星系的总热红外光度、SFR和恒星质量。在z ~ 0.7时，近40%的中、高质量星系（恒星质量≥2 × 1010 M）正在经历一个高于过去平均SFR的强烈星星形成期。相比之下，在本地宇宙中，只有不到1%的同等质量星系具有类似的强烈星星形成活动。形态上未受干扰的星系主导了总的红外光度密度和SFR密度：在z ~ 0.7时，超过一半的强烈恒星形成星系具有螺旋形态，而不到30%的星系具有强烈的相互作用。因此，主要合并率的下降并不是自z ~ 0.7以来宇宙SFR快速下降的根本原因。对星系形态没有强烈影响的物理性质，例如气体消耗和与小卫星星系的弱相互作用，似乎是原因。
We present a first analysis of deep 24 μm observations with the Spitzer Space Telescope of a sample of nearly 1500 galaxies in a thin redshift slice, 0.65 ≤ z < 0.75. We combine the infrared data with redshifts, rest-frame luminosities, and colors from COMBO-17 and with morphologies from Hubble Space Telescope images collected by the Galaxy Evolution from Morphology and SEDs (GEMS) and Great Observatories Origins Deep Survey (GOODS) projects. To characterize the decline in star formation rate (SFR) since z ~ 0.7, we estimate the total thermal IR luminosities, SFRs, and stellar masses for the galaxies in this sample. At z ~ 0.7, nearly 40% of intermediate- and high-mass galaxies (with stellar masses ≥2 × 1010 M☉) are undergoing a period of intense star formation above their past-averaged SFR. In contrast, less than 1% of equally massive galaxies in the local universe have similarly intense star formation activity. Morphologically undisturbed galaxies dominate the total infrared luminosity density and SFR density: at z ~ 0.7, more than half of the intensely star-forming galaxies have spiral morphologies, whereas less than ~30% are strongly interacting. Thus, a decline in major merger rate is not the underlying cause of the rapid decline in cosmic SFR since z ~ 0.7. Physical properties that do not strongly affect galaxy morphology—for example, gas consumption and weak interactions with small satellite galaxies—appear to be responsible.