SLOW EVOLUTION OF THE SPECIFIC STAR FORMATION RATE AT z > 2: THE IMPACT OF DUST, EMISSION LINES, AND A RISING STAR FORMATION HISTORY
SLOW EVOLUTION OF THE SPECIFIC STAR FORMATION RATE AT z > 2: THE IMPACT OF DUST, EMISSION LINES, AND A RISING STAR FORMATION HISTORY
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DOI：
10.1088/0004-637x/781/1/34
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发表时间：
2012-08
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影响因子：
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通讯作者：
V. González;R. Bouwens;G. Illingworth;I. Labbé;P. Oesch;M. Franx;D. Magee
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文献类型：
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作者：
V. González;R. Bouwens;G. Illingworth;I. Labbé;P. Oesch;M. Franx;D. Magee
我们测量的具体星星形成率（sSFR = SFR/Mstellar）的红移4和6之间的演变，以评估报告的“常数”sSFR在z > 2。通过拟合恒星星族模型和星系的光谱能量分布，我们得到了GOODS-S场中750个z 4-6星系的恒星质量和星星形成率（SFR）。尘埃消光来自于观察到的紫外线颜色。我们评估了不同的星星形成历史（SFH，常数和随时间上升）和光发射线的影响。SFR和Mstellar值对SFH是恒定还是上升不敏感。导出的sSFR在以1和5 × 109 M为中心的两个M星仓中非常相似（在0.1 dex内）。然而，发射谱线的影响相当明显。假设没有来自发射谱线的贡献，5 × 109 M星系的sSFR在z > 2时演化较弱（sSFR（z）<$（1 + z）0.6 ± 0.1），与以前的结果一致。当发射谱线包含在静止帧光学波段中时，与观察到的红外阵列相机[3.6]和[4.5]通量一致，在sSFR（z）<$（1 + z）1.0 ± 0.1之后，sSFR在高红移处显示出更高的值，即，最佳拟合演化显示，在z = 6时的sSFR比z = 2时的sSFR高2.3倍。然而，这是一个明显弱于z 2（sSFR（z）<$（1 + z）2.5）的趋势。即使考虑到发射谱线，在z > 2处观察到的sSFR（z）趋势仍然与理论预期相矛盾。
We measure the evolution of the specific star formation rate (sSFR = SFR/Mstellar) between redshift 4 and 6 to assess the reported “constant” sSFR at z > 2. We derive stellar masses and star formation rates (SFRs) for a large sample of 750 z ∼ 4–6 galaxies in the GOODS-S field by fitting stellar population models to their spectral energy distributions. Dust extinction is derived from the observed UV colors. We evaluate different star formation histories (SFHs, constant and rising with time) and the impact of optical emission lines. The SFR and Mstellar values are insensitive to whether the SFH is constant or rising. The derived sSFR is very similar (within 0.1 dex) in two Mstellar bins centered at 1 and 5 × 109 M☉. The effect of emission lines was, however, quite pronounced. Assuming no contribution from emission lines, the sSFR for galaxies at 5 × 109 M☉ evolves weakly at z > 2 (sSFR(z)∝(1 + z)0.6 ± 0.1), consistent with previous results. When emission lines are included in the rest-frame optical bands, consistent with the observed Infrared Array Camera [3.6] and [4.5] fluxes, the sSFR shows higher values at high redshift following sSFR(z)∝(1 + z)1.0 ± 0.1, i.e., the best-fit evolution shows a sSFR ∼2.3 × higher at z ∼ 6 than at z ∼ 2. This is, however, a substantially weaker trend than that found at z 2 (sSFR(z)∝(1 + z)2.5). Even accounting for emission lines, the observed sSFR(z) trends at z > 2 are still in tension with theoretical expectations.