arXiv 1503.079972015-03astro-ph.GA

SDP的高分辨率ALMA观测。II。z=3.042的透镜亚毫米星系的分子团簇性质

High-resolution ALMA Observations of SDP.81. II. Molecular Clump Properties of a Lensed Submillimeter Galaxy at z=3.042

Bunyo Hatsukade, Yoichi Tamura, Daisuke Iono, Yuichi Matsuda, Masao Hayashi, Masamune Oguri

备注：: 7 pages, 3 figures, Accepted for publication in PASJ
DOI：: 10.1093/pasj/psv061

摘要：

我们介绍了阿塔卡马大型毫米/亚毫米阵列（ALMA）在$z=3.042$上发现的引力透镜亚毫米星系H-ATLAS J090311.6+003906（SDP.81）中分子气体和尘埃的空间分辨特性。我们在CO（5-4）线数据中鉴定了14个分子团，所有分子团在源平面的空间尺度为$\sim$ 50-300 pc。团簇的分子气体面密度（$Σ_{\rm H_2}$）和恒星形成率（$Σ_{\rm SFR}$）比本星系的高出三个数量级以上。团块被放置在“突发”序列中的$Σ_{\rm H_2}$ - $Σ_{\rm SFR}$平面，这表明$z \sim 3$分子团块遵循恒星形成法律派生本地星暴星系。我们的引力透镜模型，在源平面的位置推导出的分子团，尘埃团，和恒星组件中确定的{ \sl哈勃太空望远镜}图像。分子团和尘埃团共存于$\sim$ 2千秒差距的相似区域，而恒星成分最多偏移$\sim$ 5千秒差距。分子团在南北方向上具有系统的速度梯度，这可能表明旋转的气体盘。一种可能的情况是，分子气体、尘埃和恒星的成分分布在一个数kpc尺度的旋转盘中，恒星的辐射被中心恒星形成区域的尘埃严重遮蔽。另外，SDP.81可以用合并系统来解释，在合并系统中，尘埃星暴发生在两个星系碰撞的区域，被恒星成分中的潮汐特征所包围。

英文摘要：

We present spatially-resolved properties of molecular gas and dust in a gravitationally-lensed submillimeter galaxy H-ATLAS J090311.6+003906 (SDP.81) at $z=3.042$ revealed by the Atacama Large Millimeter/submillimeter Array (ALMA). We identified 14 molecular clumps in the CO(5-4) line data, all with a spatial scale of $\sim$50-300 pc in the source plane. The surface density of molecular gas ($Σ_{\rm H_2}$) and star-formation rate ($Σ_{\rm SFR}$) of the clumps are more than three orders of magnitude higher than those found in local spiral galaxies. The clumps are placed in the `burst' sequence in the $Σ_{\rm H_2}$-$Σ_{\rm SFR}$ plane, suggesting that $z \sim 3$ molecular clumps follow the star-formation law derived for local starburst galaxies. With our gravitational lens model, the positions in the source plane are derived for the molecular clumps, dust clumps, and stellar components identified in the {\sl Hubble Space Telescope} image. The molecular and dust clumps coexist in a similar region over $\sim$2 kpc, while the stellar components are offset at most by $\sim$5 kpc. The molecular clumps have a systematic velocity gradient in the north-south direction, which may indicate a rotating gas disk. One possible scenario is that the components of molecular gas, dust, and stars are distributed in a several-kpc scale rotating disk, and the stellar emission is heavily obscured by dust in the central star-forming region. Alternatively, SDP.81 can be explained by a merging system, where dusty starbursts occur in the region where the two galaxies collide, surrounded by tidal features traced in the stellar components.

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