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arXiv 1602.05904astro-ph.GA
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射电星系Pictor A环核区的积分场谱

Integral Field Spectroscopy of the circumnuclear region of the Radio Galaxy Pictor A

Guilherme S. Couto, Thaisa Storchi-Bergmann, Andrew Robinson, Rogemar A. Riffel, Preeti Kharb, Davide Lena, Allan Schnorr-Müller

摘要:

本文介绍宽线射电星系Pictor A的内部$2.5 \times 3.4$ kpc $^2$的光学积分场光谱,空间分辨率为$\approx 400$ pc。在整个视场中观察到线发射,在核和沿着PA $\sim 70^\circ$从西南到东北穿过核的细长线性特征(ELF)中最强。虽然宽的双峰H $α$谱线和[OI]6300/H $α$和[SII]6717+31/H $α$比值是活动星系核的典型特征,但[NII]6584/H $α$比值(0.15 - 0.25)异常低。我们认为这是由于气体的金属含量异常低。质心速度图显示主要是蓝移到南部和红移到北部的核,但速度场是不是很好地拟合的旋转模型。沿极低频的速度色散很低(< 100 km/s $^{-1}$),排除了作为这种结构起源的喷流-云相互作用。ELF在通道图中显示出蓝移和红移,这表明它接近天空平面。ELF显然是被AGN光电离的,但其运动学和推断的低金属丰度表明,这种结构可能起源于过去与另一个星系的合并事件。我们认为,在这种相互作用中获得的气体可能是喂养ELF。

英文摘要:

We present optical integral field spectroscopy of the inner $2.5 \times 3.4$ kpc$^2$ of the broad-line radio galaxy Pictor A, at a spatial resolution of $\approx 400$ pc. Line emission is observed over the whole field-of-view, being strongest at the nucleus and in an elongated linear feature (ELF) crossing the nucleus from the south-west to the north-east along PA $\sim 70^\circ$. Although the broad double-peaked H$α$ line and the [OI]6300/H$α$ and [SII]6717+31/H$α$ ratios are typical of AGNs, the [NII]6584/H$α$ ratio (0.15 - 0.25) is unusually low. We suggest that this is due to the unusually low metallicity of the gas. Centroid velocity maps show mostly blueshifts to the south and redshifts to the north of the nucleus, but the velocity field is not well fitted by a rotation model. Velocity dispersions are low (< 100 km s$^{-1}$) along the ELF, ruling out a jet-cloud interaction as the origin of this structure. The ELF shows both blueshifts and redshifts in channel maps, suggesting that it is close to the plane of the sky. The ELF is evidently photoionized by the AGN, but its kinematics and inferred low metallicity suggest that this structure may have originated in a past merger event with another galaxy. We suggest that the gas acquired in this interaction may be feeding the ELF.

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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