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北美退伍军人节(Veterans Day),12 日无更新
arXiv 1609.01308astro-ph.GAastro-ph.HE
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来自NVSS和TGSS的无线电频谱指数

Radio spectral index from NVSS and TGSS

Prabhakar Tiwari

摘要:

我从150 MHz TIFR GMRT巡天(TGSS)和1.4 GHz NRAO VLA巡天(NVSS)中观测到的541,195个常见源中提取射电频谱指数$α$。这个大型的共同源星表覆盖了大约$80\%$的天空。在这些调查的流量密度限制是这样的,观察到的星系可能是活动星系核(AGN)的主机。我确认了这个大样本的$α$的陡峭度随着通量密度的增加而增加,并提供了$α$和通量密度之间的参数拟合。接下来,我把数据分成一个低通量(LF)和一个高通量(HF)密度样本,样本中的星系数量大致相等。LF样本包含所有低于100 mJy TGSS和20 mJy NVSS通量密度的星系,HF样本包含所有高于100 mJy TGSS和20 mJy NVSS的星系。我观察到$α$随源尺寸(TGSS测量)增加,对于LF和HF源,分别饱和到大尺寸的$0.89\pm0.22$和$0.76\pm 0.21$。我讨论了观察到的结果和可能的物理机制来解释所观察到的$α$依赖于LF和HF样品的源大小。

英文摘要:

I extract the radio spectral index, $α$, from 541,195 common sources observed in the 150 MHz TIFR GMRT Sky Survey (TGSS) and the 1.4 GHz NRAO VLA Sky Survey (NVSS). This large common source catalogue covers about $80\%$ of the sky. The flux density limits in these surveys are such that the observed galaxies are presumably hosts of active galactic nuclei (AGNs). I confirm the steepening of $α$ with increasing flux density for this large sample and provide a parametric fit between $α$ and flux density. Next, I divide the data into a low flux (LF) and a high flux (HF) density sample of roughly equal number of galaxies. The LF sample contains all galaxies below 100 mJy TGSS and 20 mJy NVSS flux density and the HF sample is all galaxies above 100 mJy TGSS and 20 mJy NVSS. I observe an increase in $α$ with source size (TGSS measured), saturating for large sizes to $0.89\pm0.22$ and $0.76\pm 0.21$ for the LF and HF sources, respectively. I discuss the observed results and possible physical mechanisms to explain observed $α$ dependence with source size for LF and HF samples.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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