High-redshift quasars along the main sequence

Abstract

Context. The 4-Dimensional Eigenvector 1 empirical formalism (4DE1) and its Main Sequence (MS) for quasars emerged as a powerful tool to organise the quasar diversity since several key observational measures and physical parameters are systematically changing along it. Aims. The trends of the 4DE1 are very well established to explain all the diversity seen in low-redshift quasar samples. Nevertheless, the situation is by far less clear when dealing with high-luminosity and high-redshift sources. We aim to evaluate the behaviour of our 22 high-redshift (2.2 ≤ z ≤ 3.7) and high-luminosity (47.39 ≤ L bol ≤ 48.36) quasars in the context of the 4DE1. Methods. Our approach involves studying quasar physics through spectroscopic exploration of UV and optical emission line diagnostics. We are using new observations from the ISAAC instrument at ESO-VLT and mainly from the SDSS to cover the optical and the UV rest-frames, respectively. Emission lines are characterised both through a quantitative parametrisation of the line profiles, and by decomposing the emission line profiles using multicomponent fitting routines. Results. We provide spectrophotometric properties and line profile measurements for Hβ+[O iii]λλ4959,5007, as well as for Si ivλ1397+O iv]λ1402, C ivλ1549+He iiλ1640, 1900 Å blend (including Al iiiλ1860, Si iii]λ1892, and C iii]λ1909). Six out of the 22 objects present a significant blueshifted component on the Hβ profile, and in 14/22 cases an Hβ outflowing component associated to [O iii] is detected. The majority of [O iii]λλ4959,5007 emission line profiles show blueshifted velocities larger than 250 km s −1 . We reveal extremely broad [O iii]λλ4959,5007 emission that is comparable to the width of Hβ broad profile in some highly accreting quasars. [O iii]λλ4959,5007 and C ivλ1549 blueshifts show very high amplitudes and a high degree of correlation. Line width and shift are correlated for both [O iii]λλ4959,5007 and C ivλ1549, suggesting that emission from outflowing gas is providing a substantial broadening to both lines. Otherwise, the links between C ivλ1549 centroid velocity at half intensity (c(1/2)), Eddington ratio (L/L Edd ), and bolometric luminosity are found to be in agreement with previous studies of high-luminosity quasars. Conclusions. Our analysis suggests that the behaviour of quasars of very high luminosity all along the main sequence is strongly affected by powerful outflows involving a broad range of spatial scales. The main sequence correlations remain valid at high redshift and high luminosity even if a systematic increase in line width is observed. Scaling laws based on UV Al iiiλ1860 and Hβ emission lines are equally reliable estimators of M BH .

The Correlation Luminosity-Velocity Dispersion of Galaxies and Active Galactic Nuclei

“…A connection between quasars observational and accretion parameters has become possible only after the systematic organization of the diverse spectral properties along an easily identified sequence (the so-called Eigenvector-1 sequence or quasar main sequence [14,[33][34][35]). Since then, two main populations and several spectral types along the sequence have provided contextualization for most type-1 AGN [36,37], in both low and high luminosity samples [38,39]. The distinction between the two populations-conventionally named A and B-is rooted in systematic differences in terms of Eddington ratio, which in turn translates into the possibility of two different accretion modes [40,41].…”

“…We have applied a non-linear, multicomponent fitting technique [229] implemented in the data analysis package IRAF [230] to adequately subtract the AGN continuum emission and deconvolve the Hβ profile from its contaminants. The same technique has been successfully applied in a number of earlier papers [39,115,200,231,232].…”

Joint Analysis of the Iron Emission in the Optical and Near-Infrared Spectrum of I Zw 1

“…[47] shows a strong correlation between the optical FeII emission within the spectral range of 4434-4684 Å(centered at the wavelength 4570 Å), the peak intensity of [OIII]λ5007 oxygen emission line and the full width at half maximum (FWHM) of the broad component of the Balmer Hβ hydrogen emission profile. This led to the well-defined FWHM(Hβ) versus R FeII connection (R FeII generally denotes the ratio of the integrated FeII emission within 4434-4684 Å to the broad Hβ emission), that is, the well-known optical plane of the quasar main sequence [4,24,26,[55][56][57][58]. Within this framework, FeII emission not only plays a crucial role in discerning the underlying factors driving EV1 [4] but also serves as a link between line strength and the emitting gas physics for a diverse population of Type-1 AGNs along the EV1 plane.…”