We present the spectra of 14 quasars with a wide coverage of rest wavelengths from 1000 to 7300 8. The redshift ranges from z ¼ 0:061 to 0.555 and the luminosity from M B ¼ À22:69 to À26.32. 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 8. 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 k2798 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 (U 1 [2200-2660 8], U 2 [2660-3000 8], U 3 [3000-3500 8], O1 [4400-4700 8], and O2 [5100-5600 8]), the total flux of Balmer continuum, and the fluxes of Mg ii k2798, H, 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 H FWHM, (2) larger À for fainter M B , (3) smaller Mg ii FWHM for larger À, (4) larger Mg ii FWHM for smaller Fe ii(O1)/ Mg ii, (5) larger M BH for smaller À, (6) larger M BH for smaller Fe ii(O1)/ Mg ii, (7) larger [O iii]/H for larger Mg ii FWHM, and (8) larger Fe ii(O1)/ Mg ii for larger Fe ii(O1)/ Fe ii(U 1).The fact that six of these eight are related to FWHM or M BH (/ FWHM 2 ) may imply that M BH is a fundamental quantity that controls À 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(U 1) is found to tightly correlate with Fe ii(O1)/ Mg ii, but not with Fe ii(U 1)/ Mg ii.
We present results of the near-infrared (IR) spectroscopy of six quasars whose redshifts range from 0.158 to 1.084. Combined with the satellite ultraviolet data, the relative line strengths of O I λ1304, O I λ8446, O I λ11287, and the near-IR Ca II triplet are given. In addition, the corresponding O I line strengths measured in normal Seyfert 1s and narrow-line Seyfert 1s are collected from the literature. These lines are thought to emerge from the same gas as do the Fe II lines, so they are good tracers of the Fe II emission region within a broad emission line region (BELR) in active galactic nuclei (AGNs). In order to reveal the physical condition within the relevant emission region, we performed photoionized model calculations and compared them to the observations. It suggests that a rather dense gas with density n H ∼ 10 11.5 cm −3 is present at an outer portion of the BELR, illuminated by the ionizing radiation corresponding to an ionization parameter U ∼ 10 −2.5 and is primarily responsible for the observed O I, Ca II, and Fe II lines, based on the resemblance of their profiles. The three O I lines
We present rest-frame optical/near-infrared spectra of the gravitationally lensed quasar APM 08279+5255 at z = 3.91 that has been taken using the Infrared Camera (IRC) onboard the AKARI infrared satellite. The observed continuum consists of two components; a power-law component dominating optical wavelengths which is the direct light from the central source and thermal emission dominating near-infrared wavelengths which is attributed to the emission from hot dust in the circumnuclear region. The thermal emission well represents optically thick emission by hot dust at T ∼ 1300K with τ 2µm > 2 and apparent mass, M hot > 10M ⊙ . Thus, our observations directly detected the optically thick region of hot dust in APM 08279+5255. HI recombination lines of Hα(0.656µm), Paα(1.875µm), and Paβ(1.282µm) are clearly detected at 3.2, 6.3, and 9.3 µm. Simulations with the photoionization models suggest that APM 08279+5255 has BLR(Broad Line Region) clouds characterized by log n H ∼ 12 − 14 for the gas density, log U ∼ −2 − −6 for the ionization parameter, and E(B − V ) ∼ 0.3 − 0.6 for the broad line region. Thus, optically thick emission of hot dust support an idea on non-spherical distribution of dust near the central source, consistent with the Active Galactic Nuclei model with the dust torus. The temperature of hot dust and flux ratios of these HI lines are similar to those observed in low-redshift † Based on observations with AKARI, a JAXA project with the participation of ESA.
By observing the near-infrared spectrum of the quasar PG 1116$+$215 at $z = 0.176$ and combining with the HST/FOS spectrum, we obtained the relative strengths of three permitted O i lines ($\lambda$1304, $\lambda$8446, and $\lambda$11287) in a quasar for the first time. The photon flux ratios of the O i lines of the quasar were compared with those previously measured in a Seyfert 1 and six narrow-line Seyfert 1 s. No significant differences were found in the O i line flux ratios between the quasar and the other Seyferts, suggesting that the gas density in the O i and Fe ii line-emitting regions in the quasar is of the same order as those in low-luminosity AGNs. It was also found that the line width of O i$\lambda$11287 is significantly narrower than that of Ly$\alpha$, which is consistent with O i and Fe ii emission occurring in the partly ionized regions at the outermost portion of the broad-line region where velocities are small.
We present spectra of six luminous quasars at z ∼ 2, covering rest wavelengths 1600−3200 Å. The fluxes of the UV Fe II emission lines and Mg II λ2798 doublet, the line widths of Mg II and the 3000 Å luminosity were obtained from the spectra. These quantities were compared with those of low-redshift quasars at z = 0.06-0.55 studied by Tsuzuki et al. In a plot of the Fe II(UV)/Mg II flux ratio as a function of the central black hole mass, Fe II(UV)/Mg II in our z ∼ 2 quasars is systematically greater than in the low-redshift quasars. We confirmed that luminosity is not responsible for this excess. It is unclear whether this excess is caused by rich Fe abundance at z ∼ 2 over low-redshift or by non-abundance effects such as high gas density, strong radiation field and high microturbulent velocity.Key words: galaxies: abundances -galaxies: active -line: formation -quasars: emission lines. I N T RO D U C T I O NAccording to the models of explosive nucleosynthesis, much of the iron comes from Type Ia supernovae, while α elements such as O and Mg come from Type II supernovae. Because of the difference in lifetime of the progenitors, it is generally considered that the iron enrichment delays relative to α elements by 1-2 billion years (Hamann & Ferland 1993;Yoshii, Tsujimoto & Nomoto 1996;Yoshii, Tsujimoto & Kawara 1998). If Fe II/Mg II, the relative strengths of Fe II emission lines and the Mg II λ2798 doublet, reflects the Fe/Mg abundance ratio, there will be a break in Fe II/Mg II at high redshift. Despite much efforts made by many observational groups (e.g. Elston, Thompson & Hill 1994;Kawara et al. 1996;Dietrich et al. 2002Dietrich et al. , 2003Iwamuro et al. 2002Iwamuro et al. , 2004Freudling, Corbin & Korista 2003;Maiolino et al. 2003;Tsuzuki et al. 2006;Kurk et al. 2007;Matsuoka et al. 2007;Matsuoka, Kawara & Oyabu 2008), there have been found no signs of such a break; Fe II/Mg II looks constant from low-redshift up to z ∼ 6.5 with large scatter.No break in Fe II/Mg II might reflect a significantly shorter delaytime of 0.2-0.6 Gyr, as suggested by Friaça & Terlevich (1998), Matteucci & Recchi (2001) and Granato et al. (2004). The expected break can also be obscured by non-abundance effects. Simulations of Fe II emitting regions, assuming either photoionization or shocks, imply that the Fe abundance is not the only parameter which controls E-mail: hsameshima@ioa.s.u-tokyo.ac.jp the Fe II strength, but several non-abundance factors can also affect it. Such non-abundance factors include spectral energy distribution (SED) of the central source, strength of the radiation field and the gas density of broad emission line region (BELR) clouds. Recently, Verner et al. (2003) and Baldwin et al. (2004) pointed out that a large microturbulence velocity might be responsible for strong Fe II emission. Tsuzuki et al. (2006) have studied non-abundance factors by using spectra of a low-redshift sample of 14 quasars, covering wide rest wavlengths 1000-7300 Å, and claimed that the Fe II strength correlates with the mass ...
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