大爆炸后14亿年通过湿合并形成类星体宿主星系
Formation of a Quasar Host Galaxy through a Wet Merger 1.4 Billion Years after the Big Bang
摘要：
我们提出了高红移类星体BRI 1335-0417（z=4.41）的宿主星系中的分子气体的高分辨率甚大阵列成像。我们的CO（2-1）观测具有0.15”（1.0 kpc）的线性分辨率，并在空间和速度上解析分子气体发射。BRI 1335-0417中的分子气体扩展到5 kpc的尺度，并显示出复杂的结构。在速度空间中，至少有三个不同的组分，它们的分子质量约占9.2 × 10^10 M_sun总分子质量的三分之二，它们嵌在一个结构中，该结构约占系统总分子质量的三分之一。最亮的CO（2-1）谱线发射区在1 kpc直径范围内具有61+/-9K的峰值亮度温度，这与CO谱线激发预测的动力学气体温度相当。这也与附近超亮红外星系中心区域的气体温度相当，但这些星系比1千秒差距要紧凑得多。BRI 1335-0417中分子库的空间和速度结构与简单的引力束缚盘不一致，但类似于合并系统。我们的观测结果与一个主要的、富含气体的（“湿”）合并相一致，它既为一个吸积的超大质量黑洞提供了能量（导致了明亮的类星体活动），又为一个巨大的恒星暴提供了燃料，从而形成了这个星系中的恒星隆起。因此，我们对z>4类星体宿主星系的研究可能是高红移的“湿”合并与活动星系核活动有关的最直接的观测证据。
英文摘要：
We present high-resolution Very Large Array imaging of the molecular gas in the host galaxy of the high redshift quasar BRI 1335-0417 (z=4.41). Our CO(2-1) observations have a linear resolution of 0.15" (1.0 kpc) and resolve the molecular gas emission both spatially and in velocity. The molecular gas in BRI 1335-0417 is extended on scales of 5 kpc, and shows a complex structure. At least three distinct components encompassing about two thirds of the total molecular mass of 9.2 x 10^10 M_sun are identified in velocity space, which are embedded in a structure that harbors about one third of the total molecular mass in the system. The brightest CO(2-1) line emission region has a peak brightness temperature of 61+/-9 K within 1 kpc diameter, which is comparable to the kinetic gas temperature as predicted from the CO line excitation. This is also comparable to the gas temperatures found in the central regions of nearby ultra-luminous infrared galaxies, which are however much more compact than 1 kpc. The spatial and velocity structure of the molecular reservoir in BRI 1335-0417 is inconsistent with a simple gravitationally bound disk, but resembles a merging system. Our observations are consistent with a major, gas-rich (`wet') merger that both feeds an accreting supermassive black hole (causing the bright quasar activity), and fuels a massive starburst that builds up the stellar bulge in this galaxy. Our study of this z>4 quasar host galaxy may thus be the most direct observational evidence that `wet' mergers at high redshift are related to AGN activity.
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