Constraints on the star-formation rate of z ~ 3 LBGs with measured metallicity in the CANDELS GOODS-South field
Constraints on the star-formation rate of z ~ 3 LBGs with measured metallicity in the CANDELS GOODS-South field
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CANDELS GOODS-South 磁场中测量金属丰度对 z ~ 3 LBG 恒星形成速率的约束
DOI：
10.1051/0004-6361/201322704
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发表时间：
2014
影响因子：
6.5
通讯作者：
E. Vanzella
中科院分区：
文献类型：
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作者：
M. Castellano;V. Sommariva;A. Fontana;L. Pentericci;P. Santini;A. Grazian;R. Amorín;J. Donley;J. Dunlop;H. Ferguson;F. Fiore;A. Galametz;E. Giallongo;Yicheng Guo;Kuang;A. Koekemoer;R. Maiolino;R. McLure;D. Paris;D. Schaerer;P. Troncoso;E. Vanzella
我们分析了z~2.8-3.8的14个LBG，这是唯一一个既有金属丰度光谱测量又有深红外观测（CANDELS+HUGS调查）的样品。固定的金属丰度的人口合成模型的观测值，我们确定最适合的物理参数在不同的假设下的恒星形成的历史，也考虑了星云发射的影响。为了比较，我们确定了物体的UV斜率，并使用它来估计它们的SFR_UV99，方法是按照Meurer等人（1999）的方法校正UV光度。通过SED拟合获得的SFR（SFR_fit）与SFR_UV99之间的比较表明，无论假设的SFH如何，后者都被低估了2-10倍。其他SFR指标（无线电，远红外线，X射线，复合线）相干指示SFR比SFR_UV99大2-4倍，并与SFR_fit更接近一致。这种差异是由于通常的beta-A1600转换因子所暗示的太阳金属丰度。我们提出了一个适用于亚太阳的金属丰度LBG的精确关系：A1600 = 5.32+ 1.99 β。这种关系使灰尘校正的UV与SED配件和其他SFR指示器协调一致。我们发现，z~3星系具有亚太阳金属丰度的事实意味着全球SFRD的向上修正约1.5-2倍，这取决于对恒星种群年龄的假设。我们为所有对象找到非常年轻的最佳年龄（10-500百万年）。从仔细检查的不确定性的适合和幅度的巴耳末破裂，我们得出结论，有很少的证据表明，存在的老恒星人口在我们的样本中至少有一半的LBG，这表明这些对象可能是在一个巨大的恒星形成爆发，而不是一个平稳的演变的结果。
We analyse 14 LBGs at z~2.8-3.8 constituting the only sample where both a spectroscopic measurement of their metallicity and deep IR observations (CANDELS+HUGS survey) are available. Fixing the metallicity of population synthesis models to the observed values, we determine best-fit physical parameters under different assumptions about the star-formation history and also consider the effect of nebular emission. For comparison we determine the UV slope of the objects, and use it to estimate their SFR_UV99 by correcting the UV luminosity following Meurer et al. (1999). A comparison between SFR obtained through SED-fitting (SFR_fit) and the SFR_UV99 shows that the latter are underestimated by a factor 2-10, regardless of the assumed SFH. Other SFR indicators (radio, far-IR, X-ray, recombination lines) coherently indicate SFRs a factor of 2-4 larger than SFR_UV99 and in closer agreement with SFR_fit. This discrepancy is due to the solar metallicity implied by the usual beta-A1600 conversion factor. We propose a refined relation, appropriate for sub-solar metallicity LBGs: A1600 = 5.32+1.99beta. This relation reconciles the dust-corrected UV with the SED-fitting and the other SFR indicators. We show that the fact that z~3 galaxies have sub-solar metallicity implies an upward revision by a factor of ~1.5-2 of the global SFRD, depending on the assumptions about the age of the stellar populations. We find very young best-fit ages (10-500 Myrs) for all our objects. From a careful examination of the uncertainties in the fit and the amplitude of the Balmer break we conclude that there is little evidence of the presence of old stellar population in at least half of the LBGs in our sample, suggesting that these objects are probably caught during a huge star-formation burst, rather than being the result of a smooth evolution.
DOI：
10.1088/0004-637x/769/1/80
发表时间：
2013-05
期刊：
The Astrophysical Journal
影响因子：
--
作者：
M. Ashby;S. Willner;G. Fazio;J.-S. Huang;R. Arendt;P. Barmby;G. Barro;E. Bell;R. Bouwens
通讯作者：
M. Ashby;S. Willner;G. Fazio;J.-S. Huang;R. Arendt;P. Barmby;G. Barro;E. Bell;R. Bouwens