Molecules at z=0.89 A 4-mm-rest-frame absorption-line survey toward PKS 1830-211
Molecules at z=0.89 A 4-mm-rest-frame absorption-line survey toward PKS 1830-211
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DOI：
10.1051/0004-6361/201117096
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发表时间：
2011-11-01
影响因子：
6.5
通讯作者：
Longmore, S. N.
中科院分区：
文献类型：
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作者：
Muller, S.;Beelen, A.;Longmore, S. N.
我们提出了一个7毫米的光谱调查的分子吸收线起源于磁盘的z = 0.89螺旋星系位于前面的类星体PKS 1830-211的结果。我们的调查是与澳大利亚望远镜紧凑阵列和覆盖的频率间隔30-50千兆赫，对应于静止帧频率间隔57-94千兆赫。总共有28种不同的物种，加上8种同位素变体，被探测到朝向西南吸收区，位于距离z = 0.89星系中心约2千秒差距的地方，因此是迄今为止探测到的河外天体中分子物种数量最多的。我们的旋转图分析的结果表明，旋转温度接近宇宙微波背景温度5.14 K，我们预计在z = 0.89测量，而动力学温度高一个数量级，表明气体是亚热激发。分子分数丰度被发现是在典型的银河弥漫和半透明的云之间，并明显偏离在黑暗的云TMC 1或在银河系中心的巨型分子云Sgr B2中观察到的。碳、氮、氧和硅的同位素比值明显偏离太阳值，这可能与z = 0.89星系的年轻年龄和大质量恒星主导的核合成产物的释放有关。朝向东北吸收区，其中气体的消光和柱密度大致比朝向SW吸收区低一个数量级，仅检测到少数分子。它们的相对丰度与银河系弥漫云中的相当。我们还报告了几个新的吸收成分的发现，速度跨越-300和+170公里秒（-1）之间。最后，几个物种的线中心（e。例如，在一个实施例中，CH 3OH，NH3）被发现是显着偏移的平均速度。如果由质子-电子质量比μ随红移的变化引起，则这些偏移产生上限垂直棒Δ μ/μ垂直棒<4x 10（-6），其考虑了从大量分子物种测量的速度色散产生的运动学噪声。
We present the results of a 7 mm spectral survey of molecular absorption lines originating in the disk of a z = 0.89 spiral galaxy located in front of the quasar PKS 1830-211. Our survey was performed with the Australia Telescope Compact Array and covers the frequency interval 30-50 GHz, corresponding to the rest-frame frequency interval 57-94 GHz. A total of 28 different species, plus 8 isotopic variants, were detected toward the south-west absorption region, located about 2 kpc from the center of the z = 0.89 galaxy, which therefore has the largest number of detected molecular species of any extragalactic object so far. The results of our rotation diagram analysis show that the rotation temperatures are close to the cosmic microwave background temperature of 5.14 K that we expect to measure at z = 0.89, whereas the kinetic temperature is one order of magnitude higher, indicating that the gas is subthermally excited. The molecular fractional abundances are found to be in-between those in typical Galactic diffuse and translucent clouds, and clearly deviate from those observed in the dark cloud TMC 1 or in the Galactic center giant molecular cloud Sgr B2. The isotopic ratios of carbon, nitrogen, oxygen, and silicon deviate significantly from the solar values, which can be linked to the young age of the z = 0.89 galaxy and a release of nucleosynthesis products dominated by massive stars. Toward the north-east absorption region, where the extinction and column density of gas is roughly one order of magnitude lower than toward the SW absorption region, only a handful of molecules are detected. Their relative abundances are comparable to those in Galactic diffuse clouds. We also report the discovery of several new absorption components, with velocities spanning between -300 and +170 km s(-1). Finally, the line centroids of several species (e. g., CH3OH, NH3) are found to be significantly offset from the average velocity. If caused by a variation in the proton-to-electron mass ratio mu with redshift, these offsets yield an upper limit vertical bar Delta mu/mu vertical bar < 4x10(-6), which takes into account the kinematical noise produced by the velocity dispersion measured from a large number of molecular species.