ALMA在布满灰尘的蜘蛛网中发现露珠
ALMA Finds Dew Drops in the Dusty Spider's Web
摘要：
我们提出0。“在z=2.161的射电星系MRC 1138 -262中观测到的246 GHz连续谱、[CI]^3P_2-^3P_1精细结构线（[CI]2-1）、CO（7-6）和H2O线的5分辨率ALMA探测。我们在射电核心位置和距离它约4kpc的第二个分量中都探测到了强的[CI]2-1辐射，后者的[CI]2-1谱线宽为1100 km/s，其H2质量为1.6 × 10^10Msun，这意味着该辐射一定来自一个小于60 pc的致密区域，可能包含第二个活动星系核。使用[CI]2-1发射得到的两个物体的H2质量总和为3.3x10^10 Msun。总CO（7-6）/[Cl]2-1线通量比为0.2，表明宇宙射线主导区存在低激发分子气藏和/或增强的原子碳。我们首次在高z非透镜星系中探测到了空间分辨的H2 O2_{11}-2_02}辐射，它位于射电星系东侧的外射电瓣附近，以及射电星系西侧的射电喷流弯曲处。在两个位置都没有看到潜在的246 GHz连续辐射。我们认为H2O发射是在致密分子气体（10^{3-5} cm^-3）中慢激波（10- 40 km/s）后的冷却区激发的。扩展的水发射可能是射电喷流在冷却和形成晕和星系团间气体中的冲击后气体分子的影响的证据，类似于在低z星系团和其他高z射电星系中看到的。这些观测结果意味着，星际和星系团间介质中的射电喷流不仅会像模拟中通常假设或发现的那样将气体加热到高温，而且还会引起冷却和耗散，从而导致大量的冷致密分子气体。分子的形成和强烈的耗散可以解释在MRC 1138 - 262周围观测到的扩展的扩散分子气体和年轻恒星。
英文摘要：
We present 0."5 resolution ALMA detections of the observed 246GHz continuum, [CI]^3P_2-^3P_1 fine structure line ([CI]2-1), CO(7-6) and H2O lines in the z=2.161 radio galaxy MRC1138-262, the 'Spiderweb Galaxy'. We detect strong [CI]2-1 emission both at the position of the radio core, and in a second component ~4kpc away from it. The 1100km/s broad [CI]2-1 line in this latter component, combined with its H2 mass of 1.6x10^10Msun implies this emission must come from a compact region <60pc, possibly containing a second AGN. The combined H2 mass derived for both objects using the [CI]2-1 emission is 3.3x10^10Msun. The total CO(7-6)/[CI]2-1 line flux ratio of 0.2 suggests a low excitation molecular gas reservoir and/or enhanced atomic carbon in cosmic-ray dominated regions. We detect spatially-resolved H2O 2_{11}-2_{02} emission - for the first time in a high-z un-lensed galaxy - near the outer radio lobe to the east, and near the bend of the radio jet to the west of the radio galaxy. No underlying 246GHz continuum emission is seen at either position. We suggest that the H2O emission is excited in the cooling region behind slow (10-40km/s) shocks in dense molecular gas (10^{3-5} cm^-3). The extended water emission is likely evidence of the radio jet's impact in cooling and forming molecules in the post-shocked gas in the halo and inter-cluster gas similar to what is seen in low-z clusters and other high-z radio galaxies. These observations imply that the passage of the radio jet in the interstellar and inter-cluster medium not only heats gas to high temperatures as is commonly assumed or found in simulations, but also induces cooling and dissipation which can lead to substantial amounts of cold dense molecular gas. The formation of molecules and strong dissipation in the halo gas of MRC1138-262 may explain both the extended diffuse molecular gas and young stars observed around MRC1138-262.
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