z=3.036的GRB080607星系
A Mature Dusty Star-forming Galaxy Hosting GRB080607 at z=3.036
摘要：
本文报道了暗暴GRB 080607的宿主星系的发现，其z_GRB=3.036。GRB 080607是一个独特的例子，它的余辉高度熄灭（A_V~3 mag），但仍然足够明亮，可以获得高质量的吸收线光谱。宿主星系在深层HST WF 3/IR F160 W图像中清晰地分辨出来，并在斯皮策IRAC 3.5微米和4.5微米通道中被很好地探测到，而在凯克和麦哲伦的深层光学图像中显示很少或没有通量。极红的光红外颜色与余辉光中看到的大消光一致，这表明沿余辉视线看到的大量尘埃和气体表面质量密度不仅仅是局部的，而且可能反映了整个宿主星系的全球尘埃含量。采用早期余辉光和吸收线光谱研究得出的宿主ISM的尘埃性质和金属含量，我们进行了观测光谱能量分布的恒星星族综合分析，以约束这个暗爆发宿主的内禀光度和恒星星族。宿主星系的恒星形成速率呈指数下降，e折叠时间τ =2 Gyr，年龄约为2 Gyr。我们还得到了消光校正的恒星形成速率为SFR 125 h^{-2} M_sun/yr，恒星总质量为M_* ~ 4 × 10 ^11 h^{-2} M_sun。我们的研究提供了一个大质量的尘埃恒星形成星系对GRB宿主星系群的贡献的例子，支持了长时间GRB追踪宇宙恒星形成的概念。
英文摘要：
We report the discovery of the host galaxy of dark burst GRB080607 at z_GRB=3.036. GRB080607 is a unique case of a highly extinguished (A_V~3 mag) afterglow that was yet sufficiently bright for high-quality absorption-line spectroscopy. The host galaxy is clearly resolved in deep HST WF3/IR F160W images and well detected in the Spitzer IRAC 3.5 micron and 4.5 micron channels, while displaying little/no fluxes in deep optical images from Keck and Magellan. The extremely red optical-infrared colors are consistent with the large extinction seen in the afterglow light, suggesting that the large amount of dust and gas surface mass density seen along the afterglow sightline is not merely local but likely reflects the global dust content across the entire host galaxy. Adopting the dust properties and metallicity of the host ISM derived from studies of early-time afterglow light and absorption-line spectroscopy, we perform a stellar population synthesis analysis of the observed spectral energy distribution to constrain the intrinsic luminosity and stellar population of this dark burst host. The host galaxy is best described by an exponentially declining star formation rate of e-folding time tau=2 Gyr and an age of ~2 Gyr. We also derive an extinction corrected star formation rate of SFR 125 h^{-2} M_sun/yr and a total stellar mass of M_* ~ 4x10^11 h^{-2} M_sun. Our study provides an example of massive, dusty star-forming galaxies contributing to the GRB host galaxy population, supporting the notion that long-duration GRBs trace the bulk of cosmic star formation.
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