Ascension del Olmo

Context. Recent studies show that the radio power of quasars accreting at very high rates can reach surprisingly high values. These studies suggest that this radio emission could originate from star formation (SF); however, the lack of data does not rule out the presence of a jetted active galactic nucleus (AGN). Aims. We investigated the origin of the radio emission of a sample of 18 super-Eddington candidates, over a wide range of redshifts. These sources are expected to have an extreme radiative output per unit black hole mass, show high-velocity outflows, and are therefore thought to be prime mover of galactic evolution via radiative and mechanical feedback. Methods. We present new Karl G. Jansky Very Large Array (VLA) observations at the L , C , and X bands of these sources, which we combined with observations from the LOw-Frequency ARray (LOFAR) Two-meter Sky Survey (LoTSS) and the Very Large Array Sky Survey (VLASS). We also used optical and IR data to derive estimates of accretion and wind parameters, as well as star formation rates (SFRs), which we compared with those derived from the radio emission. Results. Based on radio variability, luminosity, morphology, radio spectral properties, radio versus IR estimates of SFR, and radio-to-mid IR flux ratio, we find that seven of our 18 targets likely have radio emission predominantly arising from SF, six from a combination of SF and AGN-related mechanisms, and only three from a core or jetted AGN origin. This result is consistent with previous studies and supports the prevalence of lower-power radio structures associated with star-forming activity rather than relativistic jets in the high Eddington ratio regime. In the same sample, however, the data suggest that three sources simultaneously exhibit super-Eddington accretion and relativistic ejections.

Context. Hickson compact groups (HCGs) offer an ideal environment for investigating galaxy transformation as a result of interactions. It has been established that the evolutionary sequence of HCGs is marked by an intermediate stage characterised by a substantial amount of H I in their intragroup medium (IGrM) in the form of tidal tails and bridges (phase 2), rapidly followed by a final stage in which no IGrM gas is found and i which their member galaxies are highly H I deficient (phase 3). Aims. Despite numerous single-dish and interferometric H I studies on the HCGs, a clear H I picture of the groups within their large-scale environment still remains to be uncovered. Taking advantage of MeerKAT’s high column density sensitivity and large field of view, we aim to investigate the rapid transformation of HCGs from the intermediate to late phases, and establish a picture of their gas content variations in the context of their large-scale environments. Methods. We performed MeerKAT observations of six HCGs that were selected to represent the intermediate and late phases of the proposed evolutionary sequence. Combining the H I observations with data from recent wide-field optical surveys, we evaluated the H I deficiencies of galaxies in a ∼30′ radius of the HCGs. Results. We find that galaxies surrounding both phases exhibit similar distributions in their gas content. Similarly, galaxies making up the cores of phase 2 HCGs are comparable to their neighbours in terms of H I deficiencies. However, phase 3 groups are over an order of magnitude more deficient than their surroundings, supporting previous findings that late-phase HCG galaxies are more evolved than their large-scale environments.

Context. Hickson Compact Groups (HCGs) are dense gravitationally bound collections of four to ten galaxies and are ideal for studying gas and star formation quenching processes. Aims. We aim to understand the transition of HCGs from possessing complex H I tidal structures (so-called phase 2 groups) to a phase where galaxies have lost most or all of their H I (phase 3). We also seek to detect diffuse H I gas that was previously missed by the Very Large Array (VLA). Methods. We observed three phase 2 and three phase 3 HCGs with MeerKAT and reduced the data using the Containerized Automated Radio Astronomy Calibration (CARACal) pipeline. We produced data cubes, moment maps, and integrated spectra, and we compared our findings with previous VLA and Green Bank Telescope observations. Results. Compared with previous VLA observations, MeerKAT reveals much more extended tidal features in phase 2 and some new high surface brightness features in phase 3 groups. However, no diffuse H I component was found in phase 3 groups. We also detected many surrounding galaxies for both phase 2 and phase 3 groups, most of which are normal disc galaxies. Conclusions. The difference between phase 2 and phase 3 groups is still substantial, supporting the previous finding that the transition between the two phases must be abrupt.

This review provides an observational perspective on the fundamental properties of super-Eddington accretion onto supermassive black holes in quasars. It begins by outlining the selection criteria, particularly focusing on optical and UV broad-line intensity ratios, used to identify a population of unobscured super-Eddington candidates. Several defining features place these candidates at the extreme end of the Population A in main sequence of quasars: among them are the highest observed singly-ionized iron emission, extreme outflow velocities in UV resonance lines, and unusually high metal abundances. These key properties reflect the coexistence of a virialized sub-system within the broad-line region alongside powerful outflows, with the observed gas enrichment likely driven by nuclear or circumnuclear star formation. The most compelling evidence for the occurrence of super-Eddington accretion onto supermassive black holes comes from recent observations of massive black holes at early cosmic epochs. These black holes require rapid growth rates that are only achievable through radiatively inefficient super-Eddington accretion. Furthermore, extreme Eddington ratios, close to or slightly exceeding unity, are consistent with the saturation of radiative output per unit mass predicted by accretion disk theory for super-Eddington accretion rates. The extreme properties of super-Eddington candidates suggest that these quasars could make them stable and well-defined cosmological distance indicators, leveraging the correlation between broad-line width and luminosity expected in virialized systems. Finally, several analogies with accretion processes around stellar-mass black holes, particularly in the high/soft state, are explored to provide additional insight into the mechanisms driving super-Eddington accretion.

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.

Context. The main sequence of quasars has emerged as a powerful tool for organizing the observational and physical characteristics of type-1 active galactic nuclei (AGNs). Aims. In this study, we present a comprehensive analysis of the metallicity of the gas in the broad-line region, incorporating both new data and previously published findings, to assess the presence of any trend along the main sequence. Methods. We performed a multicomponent analysis on the strongest ultraviolet (UV) and optical emission lines for a sample of 13 radio quiet quasars in the 0.009 ≤ z ≤ 0.472 redshift range, selected based on the availability of multiwavelength data. We employed UV and optical data obtained from the Hubble Space Telescope (mainly from the Cosmic Origins Spectrograph and Faint Object Spectrograph) and several ground-based observatories, respectively. We then measured ten diagnostic ratios and compared them with the prediction of CLOUDY photoionization simulations, identifying the closest photoionization solution to the data. Results. Our investigation reveals a consistent pattern along the main sequence. We observe a systematic progression in metallicity, ranging from subsolar values to metallicity levels several times higher than solar values. Conclusions. These findings underscore the fundamental role of metallicity in correlating with the main sequence of quasars. Extreme metallicity values, at least several dozen times the solar metallicity, are confirmed in low-z AGNs radiating at a high Eddington ratio, although the origin of the extreme enrichment remains open to debate.

Despite the increasing prevalence of 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 RQ quasars remains somewhat limited. Disentangling the real impact of the radio-loudness and accretion on the outflow parameters remains a challenge to this day. We present 10 new spectra of high-z high-L quasars, combined with previous data at both high and low z and evaluate the role of the feedback from RL and RQ AGN. The final high-z high-L sample consists of a combination of 60 quasars from our ISAAC and the Hamburg-ESO surveys. The low-z sample has 84 quasars with optical and FOS reanalyzed data. We perform a multicomponent analysis of optical and UV emission line profiles along the quasar MS, and provide a relation to estimate the outflow main parameters in both the BLR and NLR through the analysis of the [OIII]5007 and CIV1549 emission lines. High-ionization lines usually present a significant asymmetry towards the blue especially in RQ that is strong evidence of outflow motions. In the ISAAC sample, 72% of the quasars present significant O[III] outflows, with c(1/2) ~ -250 km/s. RL tend to present slightly more modest blueshifted components. The behavior of [OIII]5007 mirrors the one of CIV1549, with blueshift amplitudes between the two lines showing a high degree of correlation that appears unaffected by the presence of radio emission. Both RL and RQ AGN outflow parameters at high L 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, suggesting a potential role of radioloudness in mitigating outflow effects. Nevertheless, the radio-loudness effect on the AGN feedback is much less significant than the one of accretion that emerges as the main driver of the nuclear outflows.

Context.An optically thick, geometrically thin accretion disk (AD) around a supermassive black hole might contribute to broad-line emission in type 1 active galactic nuclei (AGN). However, the emission line profiles are most often not immediately consistent with the profiles expected from a rotating disk. The extent to which an AD in AGN contributes to the broad Balmer lines and high-ionization UV lines in radio-loud (RL) AGN needs to be investigated.Aims.This work aims to determine whether the AD can account for the double-peaked profiles observed in the Balmer lines (Hβ, Hα), near-UV (MgIIλ2800), and high-ionization UV lines (C IVλ1549, CIII]λ1909) of the extremely jetted quasar3C 47.Methods.The low ionization lines (LILs) (Hβ, Hα, and Mg IIλ2800) were analyzed using a relativistic Keplerian AD model. Fits were carried out following Bayesian and multicomponent nonlinear approaches. The profiles of prototypical high ionization lines (HILs) were also modeled by the contribution of the AD, along with fairly symmetric additional components.Results.The LIL profiles of3C 47agree very well with a relativistic Keplerian AD model. The disk emission is constrained between ≈10²and ≈10³gravitational radii, with a viewing angle of ≈ 30 degrees.Conclusions.The study provides convincing direct observational evidence for the presence of an AD and explains that the HIL profiles are due to disk and failed-wind contributions. The agreement between the observed profiles of the LILs and the model is remarkable. The main alternative, a double broad-line region associated with a binary black hole, is found to be less favored than the disk model for the quasar3C 47.