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arXiv 1003.3717astro-ph.GA
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z ~ 2尘埃大质量星系中的“暗”GRB 080325

"Dark" GRB 080325 in a Dusty Massive Galaxy at z ~ 2

T. Hashimoto, K. Ohta, K. Aoki, I. Tanaka, K. Yabe, N. Kawai, W. Aoki, H. Furusawa, T. Hattori, M. Iye, K. S. Kawabata, N. Kobayashi, Y. Komiyama, G. Kosugi, Y.… 展开作者

T. Hashimoto, K. Ohta, K. Aoki, I. Tanaka, K. Yabe, N. Kawai, W. Aoki, H. Furusawa, T. Hattori, M. Iye, K. S. Kawabata, N. Kobayashi, Y. Komiyama, G. Kosugi, Y. Minowa, Y. Mizumoto, Y. Niino, K. Nomoto, J. Noumaru, R. Ogasawara, T. -S. Pyo, T. Sakamoto, K. Sekiguchi, Y. Shirasaki, M. Suzuki, A. Tajitsu, T. Takata, T. Tamagawa, H. Terada, T. Totani, J. Watanabe, T. Yamada, A. Yoshida

摘要:

我们目前的光学和近红外观测GRB 080325归类为“暗GRB”。斯巴鲁/MOIRCS的近红外观测提供了一个清晰的检测在Ks波段的余辉,虽然没有光学对应的报告。余辉的光与X射线波段的通量比表明,沿余辉视线方向的尘埃消光系数为Av = 2.7 - 10 mag.这种大的消光系数可能是GRB 080325产生光学模糊的主要原因.宿主星系的J-Ks色(AB星等中J-Ks = 1.3)比以前确定的典型GRB宿主星系的颜色要红得多。除了J和Ks波段,在B、Rc、i '和z'波段的光学图像是在爆发后一年左右用Subaru/Suprime-Cam拍摄的,宿主的光度红移估计为z_{photo} = 1.9。在z \sim 2处,主体的亮度与L^{*}相当,而在较低的红移处,典型的GRB主体的亮度低于L ^{*}。最佳拟合的宿主恒星恒星星族合成模型表明,一个大的尘埃消光(Av = 0.8等)归因于宿主的红色性质,并且宿主星系是大质量的(M_{*} = 7.0 \times 10^{10} Msun),这是以前发现的最大质量的GRB宿主之一。通过假设z \sim 2的恒星形成星系的质量-金属丰度关系适用于GRB宿主,这个大的恒星质量表明GRB 080325周围的高金属丰度环境,与推断的大灭绝一致。

英文摘要:

We present optical and near infrared observations of GRB 080325 classified as a "Dark GRB". Near-infrared observations with Subaru/MOIRCS provided a clear detection of afterglow in Ks band, although no optical counterpart was reported. The flux ratio of rest-wavelength optical to X-ray bands of the afterglow indicates that the dust extinction along the line of sight to the afterglow is Av = 2.7 - 10 mag. This large extinction is probably the major reason for optical faintness of GRB 080325. The J - Ks color of the host galaxy, (J - Ks = 1.3 in AB magnitude), is significantly redder than those for typical GRB hosts previously identified. In addition to J and Ks bands, optical images in B, Rc, i', and z' bands with Subaru/Suprime-Cam were obtained at about one year after the burst, and a photometric redshift of the host is estimated to be z_{photo} = 1.9. The host luminosity is comparable to L^{*} at z \sim 2 in contrast to the sub-L^{*} property of typical GRB hosts at lower redshifts. The best-fit stellar population synthesis model for the host shows that a large dust extinction (Av = 0.8 mag) attributes to the red nature of the host and that the host galaxy is massive (M_{*} = 7.0 \times 10^{10} Msun) which is one of the most massive GRB hosts previously identified. By assuming that the mass-metallicity relation for star-forming galaxies at z \sim 2 is applicable for the GRB host, this large stellar mass suggests the high metallicity environment around GRB 080325, consistent with inferred large extinction.

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