arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1209.5741astro-ph.CO
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哈勃空间望远镜z = 1-1.5恒星形成星系的H-α成像:巨大HII区域的大小和光度的演化

Hubble Space Telescope H-alpha imaging of star-forming galaxies at z = 1-1.5: evolution in the size and luminosity of giant HII regions

R. C. Livermore, T. Jones, J. Richard, R. G. Bower, R. S. Ellis, A. M. Swinbank, J. R. Rigby, Ian Smail, H. Ebeling, R. A. Crain

摘要:

我们提出了HST/WFC 3窄带成像的H-α发射在一个样本的8个引力透镜星系在z = 1 - 1.5。前景星系团所引起的放大率使我们能够获得360 pc的中值源平面空间分辨率,以及提供从~ 10倍到~ 50倍的通量放大率。这使我们能够识别出这个时期的恒星形成HII区域,从而研究它们的H-alpha光度分布,并与z ~ 2和本地宇宙中的等效样本进行比较。我们发现HII区域的亮度和表面亮度都随着红移而演变。团簇性质的分布可以用HII区光度函数来量化,该函数可以用幂律拟合,在某些截止点处具有指数突变,并且我们发现截止点随红移而变化。因此,我们的结论是,“clusional”星系被认为是在高红移,因为截止质量的演变,星系本身遵循类似的标度关系,在z = 0,但他们的HII区域更大,更亮,从而出现作为团块占主导地位的星系的形态。一个简单的理论论据的基础上的气体坍缩的规模的金斯质量在一个轻微的不稳定的磁盘表明,cluerous形态的高z星系是由竞争的影响,较高的气体分数造成的扰动更大的规模,部分补偿较高的周转频率,稳定磁盘。

英文摘要:

We present HST/WFC3 narrowband imaging of the H-alpha emission in a sample of eight gravitationally-lensed galaxies at z = 1 - 1.5. The magnification caused by the foreground clusters enables us to obtain a median source plane spatial resolution of 360pc, as well as providing magnifications in flux ranging from ~10x to ~50x. This enables us to identify resolved star-forming HII regions at this epoch and therefore study their H-alpha luminosity distributions for comparisons with equivalent samples at z ~ 2 and in the local Universe. We find evolution in the both luminosity and surface brightness of HII regions with redshift. The distribution of clump properties can be quantified with an HII region luminosity function, which can be fit by a power law with an exponential break at some cut-off, and we find that the cut-off evolves with redshift. We therefore conclude that `clumpy' galaxies are seen at high redshift because of the evolution of the cut-off mass; the galaxies themselves follow similar scaling relations to those at z = 0, but their HII regions are larger and brighter and thus appear as clumps which dominate the morphology of the galaxy. A simple theoretical argument based on gas collapsing on scales of the Jeans mass in a marginally unstable disk shows that the clumpy morphologies of high-z galaxies are driven by the competing effects of higher gas fractions causing perturbations on larger scales, partially compensated by higher epicyclic frequencies which stabilise the disk.

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