Fe II Emission in 14 Low-Redshift Quasars. I. Observations
Fe II Emission in 14 Low-Redshift Quasars. I. Observations
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DOI：
10.1086/506376
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发表时间：
2006-06
期刊：
影响因子：
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通讯作者：
Y. Tsuzuki;K. Kawara;Y. Yoshii;S. Oyabu;T. Tanabé;Y. Matsuoka
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文献类型：
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作者：
Y. Tsuzuki;K. Kawara;Y. Yoshii;S. Oyabu;T. Tanabé;Y. Matsuoka
我们给出了14个类星体的光谱，它们的静止波长范围很广，从1000到7300 nm。红移范围为z = 0.061至0.555，光度范围为MB = -22.69至-26.32。这些高质量的光谱是由哈勃太空望远镜光谱与地面望远镜光谱相结合的结果。本文描述了从窄线Seyfert 1星系I Zw 1的光谱中产生Fe II线发射的模板光谱的过程，该光谱覆盖了2200-3500和4200-5600 nm两个波长区域。我们的模板Fe II光谱是半经验的，在这个意义上，用CLOUDY光电离代码计算的合成光谱用于分离Fe II发射和Mg II λ2798线。测量Fe II发射线强度的过程是双重的：（1）通过在连续窗口中拟合幂律和巴耳末连续模型来减去连续分量，这相对不受线发射的影响，以及（2）基于Fe II模板的Fe II发射模型拟合连续减去的光谱。对包括I-Zw-1在内的14个类星体，我们得到了5个波段的Fe Ⅱ通量（U1 [2200-2660 μ m]，U2 [2660-3000 μ m]，U3 [3000-3500 μ m]，O 1 [4400-4700 μ m]，O2 [5100-5600 μ m]），Balmer连续谱的总通量，Mg II λ2798，Hα，和其它发射线，以及这些线的半高宽（FWHM）。通过假设这些量中的任何两个之间的线性关系进行回归分析。在置信水平高于99%的情况下，发现了八种相关性：（1）较大的Mg II FWHM对应较大的Hα FWHM，（2）较大的Γ对应较暗的MB，（3）较小的Mg II FWHM对应较大的Γ，（4）较大的Mg II FWHM对应较小的Fe II（O 1）/Mg II，（5）较大的MBH对应较小的Γ，（6）较大的MBH对应较小的Fe II（O 1）/Mg II，（7）较大的Mg Ⅱ半高宽对应较大的[O Ⅲ]/Hβ;（8）较大的Fe Ⅱ（O 1）/Fe Ⅱ（U1）对应较大的Fe Ⅱ（O 1）/Mg Ⅱ。这八个中的六个与FWHM或MBH（Δ FWHM 2）相关的事实可能意味着MBH是控制入射连续谱的光谱能量分布（SED）的基本量，其进而控制Fe II发射。此外，值得注意的是，发现Fe II（O 1）/Fe II（U1）与Fe II（O 1）/Mg II紧密相关，但与Fe II（U1）/Mg II无关。
We present the spectra of 14 quasars with a wide coverage of rest wavelengths from 1000 to 7300 Å. The redshift ranges from z = 0.061 to 0.555 and the luminosity from MB = -22.69 to -26.32. These spectra of high quality result from combining Hubble Space Telescope spectra with those taken from ground-based telescopes. We describe the procedure of generating the template spectrum of Fe II line emission from the spectrum of a narrow-line Seyfert 1 galaxy, I Zw 1, that covers two wavelength regions of 2200-3500 and 4200-5600 Å. Our template Fe II spectrum is semiempirical in the sense that the synthetic spectrum calculated with the CLOUDY photoionization code is used to separate the Fe II emission from the Mg II λ2798 line. The procedure of measuring the strengths of Fe II emission lines is twofold: (1) subtracting the continuum components by fitting models of the power-law and Balmer continua in the continuum windows, which are relatively free from line emissions, and (2) fitting models of the Fe II emission based on the Fe II template to the continuum-subtracted spectra. From 14 quasars including I Zw 1, we obtained the Fe II fluxes in five wavelength bands (U1 [2200-2660 Å], U2 [2660-3000 Å], U3 [3000-3500 Å], O1 [4400-4700 Å], and O2 [5100-5600 Å]), the total flux of Balmer continuum, and the fluxes of Mg II λ2798, Hα, and other emission lines, together with the full widths at half-maximum (FWHMs) of these lines. Regression analysis was performed by assuming a linear relation between any two of these quantities. Eight correlations were found with a confidence level higher than 99%: (1) larger Mg II FWHM for larger Hα FWHM, (2) larger Γ for fainter MB, (3) smaller Mg II FWHM for larger Γ, (4) larger Mg II FWHM for smaller Fe II(O1)/Mg II, (5) larger MBH for smaller Γ, (6) larger MBH for smaller Fe II(O1)/Mg II, (7) larger [O III]/Hβ for larger Mg II FWHM, and (8) larger Fe II(O1)/Mg II for larger Fe II(O1)/Fe II(U1). The fact that six of these eight are related to FWHM or MBH (∝FWHM2) may imply that MBH is a fundamental quantity that controls Γ or the spectral energy distribution (SED) of the incident continuum, which in turn controls the Fe II emission. Furthermore, it is worthy of noting that Fe II(O1)/Fe II(U1) is found to tightly correlate with Fe II(O1)/Mg II, but not with Fe II(U1)/Mg II.