论文标题
UGMRT HI 21-cm吸收观测值的两个极端倒置的光谱源
uGMRT HI 21-cm absorption observations of two extremely inverted spectrum sources
论文作者
论文摘要
我们报告了在稀有且最近发现的紧凑型无线电源类别中的HI 21-CM吸收的检测，即“极度倒置的频谱外层次无线电源（Eisers）”。可以想象，由于这些来源的光谱光谱部分光谱部分的光谱指数跨越了同步子自我吸收限制$α=+2.5 $（s（$ν$ n $ \ propto $ n $ n $nα$）。我们使用最近升级的巨型Metrewave射电望远镜（UGMRT）搜索了两个EISER的HI吸收，并在其中一个发现了吸收特征。针对来源J1209 $ -2032（$ z $ = 0.4040）检测到的强相关HI吸收意味着光学深度为0.178 $ \ pm $ \ pm $ 0.02，对应于34.8 $ \ pm $ 2.9 $ 2.9 $ \ pm $ 2.9 $ \ pm $ 2.9 $ \ times $ 10 $ 10 $^{20} $ cm $ cm $^$ cm^{ - 2} $的hi和hi中的timate ate pline ate and Paster in and Pastin中的100;针对GPC/CSS类型的紧凑型无线电源发现的最高已知的光学深度和HI柱密度，并支持该来源陡峭倒置的无线电谱的免费无吸收模型。对于其他来源，J1549 $+$ 5038（$ z $ = 2.171），我们的观察值未检测到HI吸收。
We report the detection of HI 21-cm absorption in a member of the rare and recently discovered class of compact radio sources, 'Extremely Inverted Spectrum Extragalactic Radio Sources (EISERS)'. EISERS conceivably form a special sub-class of the inverted spectrum radio galaxies since the spectral index of the optically thick part of the spectrum for these sources crosses the synchrotron self absorption limit of $α=+2.5$ (S($ν$) $\propto$ $ν^α$). We have searched for HI absorption in two EISERS using the recently upgraded Giant Metrewave Radio Telescope (uGMRT) and detected an absorption feature in one of them. The strong associated HI absorption detected against the source J1209$-$2032 ($z$=0.4040) implies an optical depth of 0.178$\pm$0.02 corresponding to an HI column density of 34.8$\pm$2.9 $\times$10$^{20}$ cm$^{-2}$, for an assumed HI spin temperature of 100 K and covering factor of 1. This is among the highest known optical depth and HI column densities found for compact radio sources of GPC/CSS type and supports the free-free absorption model for the steeply inverted radio spectrum of this source. For the other source, J1549$+$5038 ($z$ = 2.171), no HI absorption was detected in our observations.
