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arXiv 1202.1822astro-ph.COastro-ph.GA
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3D- HST中57个z~1强成星星系的空间分辨H α图和大小：盘状星系快速内-外组装的证据

Spatially resolved Halpha maps and sizes of 57 strongly star-forming galaxies at z~1 from 3D-HST: evidence for rapid inside-out assembly of disk galaxies

Erica June Nelson, Pieter G. van Dokkum, Gabriel Brammer, Natascha Forster Schreiber, Marijn Franx, Mattia Fumagalli, Shannon Patel, Hans-Walter Rix, Rosalind E… 展开作者

Erica June Nelson, Pieter G. van Dokkum, Gabriel Brammer, Natascha Forster Schreiber, Marijn Franx, Mattia Fumagalli, Shannon Patel, Hans-Walter Rix, Rosalind E. Skelton, Rachel Bezanson, Elisabete Da Cunha, Mariska Kriek, Ivo Labbe, Britt Lundgren, Ryan Quadri, Kasper B. Schmidt

备注：
ApJ Letters, in press. The public 3D-HST website is http://3dhst.research.yale.edu/Home.html
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摘要：

本文利用3D-HST棱镜巡天中Halpha等效宽度大于100埃的57个星系的Halpha和恒星连续辐射图研究了z~1处星系的形成。我们发现，Halpha发射广泛遵循静止帧R波段光，但它通常是更广泛和clusified。我们用半光半径来量化空间分布。H α有效半径r_e（H α）的中值为4.2 ± 0.1kpc，但大小范围很大，从r_e（H α）~ 1.0kpc的致密天体到r_e（H α）~ 15 kpc的扩展盘。将H α尺寸与连续体尺寸进行比较，我们发现对于全样本，<r_e（H α）/r_e（R）>=1.3 ± 0.1。也就是说，恒星的形成，正如Halpha所描绘的那样，通常发生在比静止坐标系R波段恒星连续体更大的半径上;星系的半径正在增长，并从内到外逐渐增加。对于最大的星系来说，这种效应似乎更为明显。使用测量的Halpha大小，我们得到恒星形成率表面密度。我们发现它们的范围从最大星系的~0.05 Msun yr^{-1} kpc^{-2}到最小星系的~5 Msun yr^{-1} kpc^{-2}，这意味着快速恒星形成的z~1星系的物理条件有很大的变化。最后，我们推断样本中的所有星系都具有非常高的气体质量分数，恒星质量倍增时间<5亿年。虽然其他的解释也是可能的，但一个简单的解释是，我们同时目睹了z~1处致密凸起和大圆盘的快速形成。

英文摘要：

We investigate the build-up of galaxies at z~1 using maps of Halpha and stellar continuum emission for a sample of 57 galaxies with rest-frame Halpha equivalent widths >100 Angstroms in the 3D-HST grism survey. We find that the Halpha emission broadly follows the rest-frame R-band light but that it is typically somewhat more extended and clumpy. We quantify the spatial distribution with the half-light radius. The median Halpha effective radius r_e(Halpha) is 4.2+-0.1 kpc but the sizes span a large range, from compact objects with r_e(Halpha) ~ 1.0 kpc to extended disks with r_e(Halpha) ~ 15 kpc. Comparing Halpha sizes to continuum sizes, we find <r_e(Halpha)/r_e(R)>=1.3+-0.1 for the full sample. That is, star formation, as traced by Halpha, typically occurs out to larger radii than the rest-frame R-band stellar continuum; galaxies are growing their radii and building up from the inside out. This effect appears to be somewhat more pronounced for the largest galaxies. Using the measured Halpha sizes, we derive star formation rate surface densities. We find that they range from ~0.05 Msun yr^{-1} kpc^{-2} for the largest galaxies to ~5 Msun yr^{-1} kpc^{-2} for the smallest galaxies, implying a large range in physical conditions in rapidly star-forming z~1 galaxies. Finally, we infer that all galaxies in the sample have very high gas mass fractions and stellar mass doubling times < 500 Myr. Although other explanations are also possible, a straightforward interpretation is that we are simultaneously witnessing the rapid formation of compact bulges and large disks at z~1.

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