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arXiv 2103.14280astro-ph.GA
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用MUSE观察NGC 1448中高度模糊的Seyfert 2核

The highly obscured Seyfert 2 nucleus in NGC 1448 observed with MUSE

R. B. Menezes, Patrícia da Silva, J. E. Steiner

摘要:

我们提出了一个光学数据立方体的NGC 1448的中心区域的分析,获得与多单元光谱探测器(MUSE)。钱德拉X射线数据表明,活动星系核(AGN)并不位于星系的视恒星核上,而是位于$1.75$ $\pm$ $0.22$ arcsec($139 \pm 17$ pc)的投影距离上。这可能是由AGN周围的高星际消光引起的,AGN对应于星系的真正核心,正如以前的研究所提出的那样。光学线发射区的形态和分类表明,两个电离锥围绕一个轴,位置角为$PA_{cones}$ = -50° $\pm$ 7°,具有赛弗特星系的发射线光谱特征。恒星和气体的运动学是一致的恒星和气体旋转盘周围的核,速度振幅为125公里秒$^{-1}$。沿两个电离锥区域探测到活动星系核的两个可能的外流。活动星系核的位置与NGC 1448中心最亮的发射线区域并不一致。这可能是活动星系核对观测者的高度遮蔽的结果(活动星系核实际上是康普顿厚度),主要是由一个几乎是边缘的环面造成的。另一个假设是活动星系核在过去的440年里,光度降低到过去的一半。在这种情况下,最亮的线发射区对应于活动星系核过去的“光回波”或“化石”。

英文摘要:

We present the analysis of an optical data cube of the central region of NGC 1448, obtained with the Multi Unit Spectroscopic Explorer (MUSE). Chandra X-ray data indicate that the active galactic nucleus (AGN) is not located at the apparent stellar nucleus of the galaxy, but at a projected distance of $1.75$ $\pm$ $0.22$ arcsec ($139 \pm 17$ pc). This is probably caused by the high interstellar extinction in the surroundings of the AGN, which corresponds to the true nucleus of the galaxy, as also proposed by previous studies. The morphology and classification of the optical line-emitting regions indicate two ionization cones, around an axis with a position angle of $PA_{cones}$ = -50° $\pm$ 7°, with emission-line spectra characteristic of Seyfert galaxies. The stellar and gas kinematics are consistent with a stellar and gas rotating disc around the nucleus, with a velocity amplitude of 125 km s$^{-1}$. Two probable outflows from the AGN were detected along the region of the two ionization cones. The AGN position does not coincide with the brightest line-emitting region at the centre of NGC 1448. That may be a consequence of the high obscuration from the AGN towards the observer (the AGN is actually Compton thick), mostly caused by a nearly edge-on torus. An additional hypothesis is that the AGN reduced its luminosity, during the last 440 yr, to nearly half of the value in the past. In this case, the brightest line-emitting region corresponds to a "light echo" or a "fossil" of the AGN in the past.

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