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arXiv 0807.3554astro-ph
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GRB 980425/ SN 1998 bw宿主星系的IFU观测:GRB区域的发射线比

IFU observations of the GRB 980425/SN 1998bw host galaxy: emission line ratios in GRB regions

L. Christensen, P. M. Vreeswijk, J. Sollerman, C. C. Thoene, E. Le Floc'h, K. Wiersema

摘要:

Bracksar模型预测伽马射线暴(GRB)的前身是贫金属的铁族元素。低金属丰度恒星星族的存在可以通过宿主星系中GRB位置的直接环境的特殊特征来表现。我们分析了来自GRB 980425的次发光宿主星系的强发射线,这表明了与超新星爆炸(SN 1998 bw)的第一次联系。主机有足够的大小,以允许详细的解决个别HII地区的光谱,并寻找具有特殊性质的区域接近的伽玛射线暴网站。使用积分场光谱与VIMOS,我们涵盖了大部分的高表面亮度部分的主机,包括HII地区的超新星和伽玛暴发生。GRB区的恒星形成率、红化、等效宽度和恒星质量与宿主中的其他HII区相似。极值出现在显示沃尔夫-拉叶星发射线的唯一区域,该区域位于GRB站点投影的800 pc处。强发射线诊断的所有HII区域意味着氧丰度在0.3和0.8太阳能与WR和GRB地区产生的最低值。比较测量的发射线比的样本的低红移伽玛暴主机的理论模型和观测场星系,我们发现,伽玛暴出现在一系列的金属丰度环境,而该地区一直非常年轻。类似的线比的伽玛射线暴主机相比,WR区域可以出现在空间上无法分辨的星系与明亮的HII区域附近的伽玛射线暴的位置。(节录)

英文摘要:

The collapsar model predicts that the progenitors of Gamma-ray Bursts (GRBs) are metal poor in Fe group elements. The existence of low metallicity stellar populations could manifest itself through special characteristics of the immediate environment of the GRB site in the host galaxy. We analyse the strong emission lines from the sub-luminous host galaxy of GRB 980425, which showed the first connection with a supernova explosion (SN 1998bw). The host has a sufficient size to allow detailed resolved spectroscopy of individual HII regions and to look for regions with special properties close to the the GRB site. Using integral field spectroscopy with VIMOS we cover most of the high surface brightness part of the host including the HII region where the supernova and GRB occurred. The star formation rate, reddening, equivalent width and stellar mass in the GRB region is similar to other HII regions in the host. Extreme values arise in the only region that shows emission lines from Wolf-Rayet stars; a region that lies 800 pc in projection from the GRB site. Strong emission line diagnostics of all HII regions imply oxygen abundances between 0.3 and 0.8 solar with the lowest values arising in the WR and GRB regions. Comparing the measured emission line ratios for a sample of low redshift GRB hosts to theoretical models and to observations of field galaxies, we find that GRBs arise in a range of metallicity environments while the regions are consistently very young. The similar line ratios of GRB hosts compared to the WR region can arise in spatially unresolved galaxies with bright HII regions near the GRB location. (Abridged)

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