STAR FORMATION AND DUST OBSCURATION AT z ≈ 2: GALAXIES AT THE DAWN OF DOWNSIZING
STAR FORMATION AND DUST OBSCURATION AT z ≈ 2: GALAXIES AT THE DAWN OF DOWNSIZING
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DOI：
10.1088/0004-637x/698/2/l116
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发表时间：
2009-05
期刊：
影响因子：
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通讯作者：
M. Pannella;C. Carilli;E. Daddi;H. McCracken;F. Owen;A. Renzini;V. Strazzullo;F. Civano;A. Koekem
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文献类型：
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作者：
M. Pannella;C. Carilli;E. Daddi;H. McCracken;F. Owen;A. Renzini;V. Strazzullo;F. Civano;A. Koekem
我们目前的第一个研究结果，旨在限制星星形成率（SFR）和尘埃含量的星系在z = 2。我们使用BzK选择的恒星形成星系的样本，从宇宙演化调查，进行堆叠分析的1.4 GHz的无线电连续作为不同的恒星种群属性的函数，清洗后的样品从活动星系核的污染。尘埃无偏SFR来自无线电通量假设当地的无线电-红外相关。这项工作的主要成果是：（1）比星星形成率（SSFR）在恒星质量的1倍以上和探测到的最高恒星质量之间是恒定的，（2）尘埃衰减是星系恒星质量的强函数，质量越大的星系比质量越小的天体更模糊，（3）将单一的紫外消光值应用于所有星系将导致严重低估大质量星系的SFR，（4）根据Calzetti公式对观测到的紫外光光度进行尘埃衰减校正，得到的结果与射电导出的结果非常一致，（5）随着红移从z = 2.3减小到1.4，我们的样品的平均SSFR稳定地减小到1.4的1/104，并且沿着局域宇宙减小到1.40的1/1040。这些经验的SFR将导致星系的质量急剧过度增长，如果保持所有的方式低红移，我们认为，这不会发生，因为星星的形成是逐步淬火，可能从最大的星系开始。
We present first results of a study aimed to constrain the star formation rate (SFR) and dust content of galaxies at z ≈ 2. We use a sample of BzK-selected star-forming galaxies, drawn from the Cosmic Evolution Survey, to perform a stacking analysis of their 1.4 GHz radio continuum as a function of different stellar population properties, after cleaning the sample from contamination by active galactic nuclei. Dust unbiased SFRs are derived from radio fluxes assuming the local radio-IR correlation. The main results of this work are: (1) specific star formation rate (SSFR)s are constant over about 1 dex in stellar mass and up to the highest stellar mass probed, (2) the dust attenuation is a strong function of galaxy stellar mass with more massive galaxies being more obscured than lower mass objects, (3) a single value of the UV extinction applied to all galaxies would lead to a gross underestimate of the SFR in massive galaxies, (4) correcting the observed UV luminosities for dust attenuation based on the Calzetti recipe provides results in very good agreement with the radio derived ones, (5) the mean SSFR of our sample steadily decreases by a factor of ∼4 with decreasing redshift from z = 2.3 to 1.4 and a factor of ∼40 down the local universe. These empirical SFRs would cause galaxies to dramatically overgrow in mass if maintained all the way to low redshifts; we suggest that this does not happen because star formation is progressively quenched, likely starting from the most massive galaxies.