Fe II Emission in 14 Low-Redshift Quasars. I. Observations

By Y. Tsuzuki, K. Kawara, Y. Yoshii, S. Oyabu, T. Tanabé, Y. Matsuoka. 2006

171 citations recorded by the source corpus.

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.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/2cce4a460174ebaee9f2d1e687c3051deb2a488c

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

Citations in the corpus

A Recoiling Supermassive Black Hole in the Quasar SDSS J092712.65+294344.0? (2008, methodology): “Each emission line was fit by a single Gaussian except the FeII multiplets, which were modeled by templates built from I Zw 1 (λ > 3500 Å, Véron-Cetty et al. 2004; λ < 3500 Å, Tsuzuki et al. 2006).”
Ionised outflows in z $\sim$ 2.4 quasar host galaxies (2015, methodology): “Finally we used a power-law for the continuum and, for those spectra showing FeII emission, we used the FeII template from Tsuzuki et al. (2006).”
COMPARING SINGLE-EPOCH VIRIAL BLACK HOLE MASS ESTIMATORS FOR LUMINOUS QUASARS (2012, methodology): “Templates for Fe II and Fe III emission have been constructed from the spectrum of the narrow-line Seyfert 1 galaxy, I Zw 1 (e.g., Boroson & Green 1992; Vestergaard & Wilkes 2001; Tsuzuki et al. 2006).”
Pōniuā‘ena: A Luminous z = 7.5 Quasar Hosting a 1.5 Billion Solar Mass Black Hole (2020, methodology): “We fit the near-IR spectrum with a pseudocontinuum, including a power-law continuum, Fe II template (Vestergaard & Wilkes 2001; Tsuzuki et al. 2006), and Balmer continuum (De Rosa et al. 2014).”
The Sloan Digital Sky Survey Reverberation Mapping Project: Sample Characterization (2018, methodology): “In addition to the continuum, we fit the optical and UV Fe II emission using empirical templates from the literature (e.g., Boroson & Green 1992; Vestergaard & Wilkes 2001; Tsuzuki et al. 2006; Salviander et al. 2007).”
A Combined Optical and X-ray Study of Unobscured Type 1 AGN. I. Optical Spectra and SED Modeling (2011, methodology): “(4) The power-law approximation for the underlying optical disc continuum is also widely adopted in previous and recent AGN optical spectral studies (e.g. Grandi 1982; Tsuzuki et al. 2006; Zhou et al. 2006; Landt et al. 2011).”
ESTIMATING BLACK HOLE MASSES IN ACTIVE GALACTIC NUCLEI USING THE Mg ii λ2800 EMISSION LINE (2009, methodology): “We note that in the fitting range of 2200–3500 Å the Balmer continuum is hard to be constrained and separated from the power-law continuum and Fe ii emission (cf. Figure 8 of Tsuzuki et al. 2006).”