z=2.3恒星形成星系内星际介质的性质
The Properties of the Interstellar Medium within a Star-Forming Galaxy at z=2.3
摘要：
我们提出了一个分析的分子和原子的气体排放在休息帧远红外和亚毫米，从透镜z=2.3亚毫米星系SMM J2135-0102。我们获得了非常高的信噪比检测11个过渡从3个物种和限制进一步20个过渡从9个物种。我们使用的12 CO，[CI]和HCN线强度调查的气体质量，运动学结构和星际介质（ISM）的化学，并找到强有力的证据，两相介质包括一个热的，密集的，发光的组件和一个潜在的扩展冷，低激发质量的组件。利用光解离区域模型，我们发现分子气体平均暴露在比银河系强1000倍的紫外辐射场中，恒星形成区域的特征密度为n~10^4 /cm ^3。这些条件类似于在局部ULIRGs和典型星暴星系的中心区域发现的条件，尽管该系统中的恒星形成率要高得多。12 CO谱线能量分布和谱线轮廓提供了强有力的证据，表明该系统包括多个不同条件下的运动学成分，包括温度和线比，表明云内的宇宙射线通量很高。我们发现，当在星系上积分时，气体和恒星形成表面密度似乎遵循肯尼库特-施密特关系，尽管与高分辨率亚毫米成像相比，我们的数据表明这种关系在<100 pc的尺度上破裂。凭借透镜放大，这些观测揭示了z~2.3处恒星形成和ISM的丰富信息，其细节水平仅在最近才能在z<0.1处实现，并显示了ALMA全面运行时将在无透镜星系中研究的潜在物理特性。（节录）。
英文摘要：
We present an analysis of the molecular and atomic gas emission in the rest-frame far-infrared and sub-millimetre, from the lensed z=2.3 sub-millimetre galaxy SMM J2135-0102. We obtain very high signal-to-noise detections of 11 transitions from 3 species and limits on a further 20 transitions from 9 species. We use the 12CO, [CI] and HCN line strengths to investigate the gas mass, kinematic structure and interstellar medium (ISM) chemistry, and find strong evidence for a two-phase medium comprising a hot, dense, luminous component and an underlying extended cool, low-excitation massive component. Employing photo-dissociation region models we show that on average the molecular gas is exposed to a UV radiation field that is ~1000 x more intense than the Milky Way, with star-forming regions having a characteristic density of n~10^4 /cm^3. These conditions are similar to those found in local ULIRGs and in the central regions of typical starburst galaxies, even though the star formation rate is far higher in this system. The 12CO spectral line energy distribution and line profiles give strong evidence that the system comprises multiple kinematic components with different conditions, including temperature, and line ratios suggestive of high cosmic ray flux within clouds. We show that, when integrated over the galaxy, the gas and star-formation surface densities appear to follow the Kennicutt-Schmidt relation, although when compared to high-resolution sub-mm imaging, our data suggest that this relation breaks down on scales of <100pc. By virtue of the lens amplification, these observations uncover a wealth of information on the star formation and ISM at z~2.3 at a level of detail that has only recently become possible at z<0.1, and show the potential physical properties that will be studied in unlensed galaxies when ALMA is in full operation. (Abridged).
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