arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1102.5092astro-ph.CO
收藏

在$z=6.027$发现一个可能古老的星系,由大质量星系团Abell 383多次成像

Discovery of a possibly old galaxy at $z=6.027$, multiply imaged by the massive cluster Abell 383

Johan Richard, Jean-Paul Kneib, Harald Ebeling, Dan Stark, Eiichi Egami, Andrew K. Fiedler

摘要:

我们报告发现了一个独特的$z=6.027$星系,由Abell 383星系团多次成像,并在新的哈勃太空望远镜ACS和WFC 3成像中检测到,以及在温暖的斯皮策观测中。这个星系被选为一对i-dropouts星系;它的高红移被Keck/DEIMOS在两张图像中测量到的强莱曼-α线所证实。结合哈勃和斯皮策测光校正后的污染线发射(估计是一个小的影响),我们确定了一个强大的巴尔默突破1.5等。考虑到最亮图像的放大因子为11.4+/-1.9(2.65+/-0.17等),该源的非透镜AB星等在H波段为27.2+/-0.05,对应于0.4 L* 星系,在3.6 μ m处为25.7+/-0.08。紫外线斜率与β ~2.0一致,从静止框架紫外线连续谱中,我们测量到目前的恒星形成率为2.4+/-1.1 Msol/年。无透镜的半光半径测量为300 pc,从中我们推断出恒星形成的表面密度约为10 Msol/yr/kpc 2。莱曼α辐射沿狭缝延伸约3”,相当于源平面内约5 kpc。这可以用恒星形成区周围存在更大的中性氢包层来解释。最后,拟合光谱能量分布使用7个光度数据点与简单的SED模型,我们得到以下属性:非常少的红化,推断恒星质量M*= 6 e9 Msol,推断年龄约800万年(对应的红移的形成约18)。该物体过去的恒星形成率可能比观测时强得多,这表明我们可能错过了z~6处的一小部分星系,这些星系在静止帧紫外波长中已经褪色。

英文摘要:

We report the discovery of a unique $z=6.027$ galaxy, multiply imaged by the cluster Abell 383 and detected in new Hubble Space Telescope ACS and WFC3 imaging, as well as in Warm Spitzer observations. This galaxy was selected as a pair of i-dropouts; its suspected high redshift was confirmed by the measurement of a strong Lyman-alpha line in both images using Keck/DEIMOS. Combining Hubble and Spitzer photometry after correcting for contamination by line emission (estimated to be a small effect), we identify a strong Balmer break of 1.5 magnitudes. Taking into account the magnification factor of 11.4+/-1.9 (2.65+/-0.17 mag) for the brightest image, the unlensed AB magnitude for the source is 27.2+/-0.05 in the H band, corresponding to a 0.4 L* galaxy, and 25.7+/-0.08 at 3.6 um. The UV slope is consistent with beta~2.0, and from the rest-frame UV continuum we measure a current star formation rate of 2.4+/-1.1 Msol/yr. The unlensed half-light radius is measured to be 300 pc, from which we deduce a star-forming surface density of ~10 Msol/yr/kpc2. The Lyman-alpha emission is found to be extended over ~3" along the slit, corresponding to ~5 kpc in the source plane. This can be explained by the presence of a much larger envelope of neutral hydrogen around the star-forming region. Finally, fitting the spectral energy distribution using 7 photometric data points with simple SED models, we derive the following properties: very little reddening, an inferred stellar mass of M*=6e9 Msol, and an inferred age of ~800 Myrs (corresponding to a redshift of formation of ~18). The star-formation rate of this object was likely much stronger in the past than at the time of observation, suggesting that we may be missing a fraction of galaxies at z~6 which have already faded in rest-frame UV wavelengths.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑