Extended gas in Seyfert 2 galaxies: implications for the nuclear source
Extended gas in Seyfert 2 galaxies: implications for the nuclear source
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DOI：
10.1046/j.1365-8711.2003.06397.x
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发表时间：
2003-05
影响因子：
4.8
通讯作者：
H. Fraquelli;T. Storchi-Bergmann;N. Levenson
中科院分区：
文献类型：
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作者：
H. Fraquelli;T. Storchi-Bergmann;N. Levenson
我们使用长缝光谱光学数据来推导出 18 个 Seyfert 2 星系样本的扩展发射气体的特性和核光度。根据发射线光度和比率，我们得出电离气体的密度、红化和质量，作为距原子核 2-4 kpc 距离的函数。考虑到核辐射的几何稀释，我们推导出覆盖因子的径向分布和核源发射的电离光子的最小速率。这个数字比根据 Hα 光度测量的被气体“拦截”的电离光子速率获得的数字大一个数量级。建议进行校准以从观测到的光度中恢复该数字。 He II λ4686/Hβ 线比用于计算电离光谱能量分布 (SED) 的斜率，该斜率与电离光子的数量相结合，可以计算硬 X 射线光度。这些光度与八种情况下的 X 射线光谱得出的光度一致，这些数据可用于恢复康普顿厚情况下的本征 X 射线发射。因此，对于难以获得的情况，我们的方法可以提供对 Seyfert 2 星系中 X 射线通量的可靠估计。我们还使用电离 SED 和光度来预测红外光度，假设红外光度主要是来自尘埃环面的再处理辐射，并发现与观测到的 IRAS 光度非常一致。
We use long-slit spectroscopic optical data to derive the properties of the extended emitting gas and the nuclear luminosity of a sample of 18 Seyfert 2 galaxies. From the emissionline luminosities and ratios we derive the density, reddening and mass of the ionized gas as a function of distance up to 2‐4 kpc from the nucleus. Taking into account the geometric dilution of the nuclear radiation, we derive the radial distribution of covering factors and the minimum rate of ionizing photons emitted by the nuclear source. This number is an order of magnitude larger than that obtained from the rate of ionizing photons ‘intercepted’ by the gas and measured from the Hα luminosity. A calibration is proposed to recover this number from the observed luminosity. The He II λ4686/Hβ line ratio was used to calculate the slope of the ionizing spectral energy distribution (SED), which in combination with the number of ionizing photons allows the calculation of the hard X-ray luminosities. These luminosities are consistent with those derived from X-ray spectra in the eight cases for which such data are available and recover the intrinsic X-ray emission in Compton-thick cases. Our method can thus provide reliable estimates of the X-ray fluxes in Seyfert 2 galaxies for the cases where it is not readily available. We also use the ionizing SED and luminosity to predict the infrared luminosity under the assumption that it is dominated by reprocessed radiation from a dusty torus, and find a good agreement with the observed IRAS luminosities.