Exploring the links between quasar winds and radio emission along the main sequence at high redshift^⋆

¹ Instituto de Astrofísica de Andalucía, IAA-CSIC, E-18008 Granada, Spain
² INAF, Osservatorio Astronomico di Padova, IT 35122 Padova, Italy

^⋆⋆ Corresponding authors; adeconto@iaa.es; chony@iaa.es; paola.marziani@inaf.it

Received: 14 March 2024
Accepted: 9 August 2024

Abstract

Context. Despite the increasing prevalence of radio-loud (RL) sources at cosmic noon, our understanding of the underlying physics that governs the accretion disc outflows in these particular sources and its dissimilarity with radio-quiet (RQ) quasars remains somewhat limited.

Aims. Disentangling the real impact of the radio-loudness and accretion on the outflow parameters remains a challenge to this day. We present ten new spectra of high-redshift and high-luminosity quasars and combine these with previous data at both high and low redshift with the aim being to evaluate the role of the feedback from RL and RQ AGN. The final high-redshift (1.5 ≲ z ≲ 3.9), high-luminosity (47.1 ≤ log(L) ≤ 48.5) sample consists of a combination of 60 quasars from our ISAAC and the Hamburg-ESO surveys. The low-redshift (z ≤ 0.8) sample has 84 quasars that have been analyzed in the optical and with the Faint Object Spectrograph (FOS) data in the UV.

Methods. We perform a multicomponent analysis of optical and UV emission line profiles along the quasar main sequence, and provide a relation that can be used to estimate the main outflow parameters (mass rate, thrust, and kinetic power) in both the BLR and NLR through the analysis of the [O III]λ5007 and C IVλ1549 emission lines.

Results. Spectrophotometric properties and line profile measurements are presented for Hβ+[O III]λλ4959,5007, Si IVλ1397+O IV]λ1402, C IVλ1549+He IIλ1640, and the 1900 Å blend. High-ionization lines, such as C IVλ1549 and [O III]λ5007, usually present a significant asymmetry toward the blue, especially in radio-quiet sources. This is strong evidence of outflow motions. In the ISAAC sample, 72% of the quasars where [O III] is clearly detected present significant outflows, with centroid velocity at half intensity blueshifted to values of greater than ∼250 km s⁻¹. Radio-loud quasars tend to present slightly more modest blueshifted components in both the UV and optical ranges. The behavior of [O III]λ5007 mirrors that of C IVλ1549, with blueshift amplitudes between the two lines showing a high degree of correlation, which appears unaffected by the presence of radio emission.

Conclusions. In contrast to the situation at low redshift, both RL and RQ AGN outflow parameters at high luminosity appear in the range needed to provide feedback effects on their host galaxies. Both high- and low-z RL quasars exhibit smaller outflows compared to RQ quasars, suggesting a potential role of radio-loudness in mitigating outflow effects. Nevertheless, the radio-loudness effect on AGN feedback is much less significant than the effect of accretion, with this latter emerging as the main driver of nuclear outflows.