Giustina Vietri

Context. Ultra-fast broad absorption line outflows (uBALs; ~ 0.1−0.2 c ) represent some of the most extreme manifestations of quasar-driven winds. With velocities reaching a significant fraction of the speed of light, they are prime candidates for efficient feedback. However, their physical structure and location remain poorly constrained, particularly at high luminosities and redshifts. In this context, variability studies offer a valuable avenue for investigating the physical conditions and geometry of these extreme outflows. Aims. We investigated the variability of uBALs through their characterisation across different epochs and multiple ionic species. Our main goal was to constrain their physical properties, locations, and kinetic powers, and to evaluate their potential impact on the respective quasar host galaxies. Methods. We performed a multi-epoch analysis of three hyper-luminous quasars from the WISSH sample, namely WISSH53, WISSH56, and WISSH71, at redshifts z = 3.628, 4.101, and 3.567, respectively. We used new and archival spectra spanning up to ~23 years of monitoring in the observed frame. We modelled absorption associated with the C IV transition using Gaussian components and accounting for covering-factor variations. We also performed a conservative analysis of multi-ion profiles (P V , Ly α , N V , and Si IV ), considering the same uBAL velocity as C IV . We derived ionic column densities and ionisation parameters, which allowed us to estimate lower and upper limits on the distances and kinetic powers of the outflows. Results. The C IV uBALs in the three sources exhibit velocities up to ~0.2 c and show significant variability across epochs, likely driven by changes in the ionisation state and/or transverse gas motion. The coordinated analysis of the multiple troughs highlights the dominant mechanisms that cause variability and enables us to derive robust lower and upper limits of the physical and energetic properties of the outflows. Outflow distances are constrained from the broad-line region (BLR) radius (~1 pc) up to a few hundred parsecs, and the kinetic powers of individual troughs reach up to ~25% of the quasar bolometric luminosity in the most extreme cases. Our results demonstrate that extreme outflows such as uBALs can inject sufficient kinetic energy to affect the host medium.

We present the first results from the WISSHFUL program, an XMM-Newton heritage program targeting luminous quasi-stellar objects (QSOs) at cosmic noon. We report on recent simultaneous XMM-Newton and NuSTAR observations of the super-Eddington accreting quasar WISSH13 at z=3.294, which provide the highest-quality broadband X-ray spectrum to date for a non-lensed QSO at this redshift. Physical modeling of the continuum reveals a soft photon index (Γ ∼ 2) and strong reflection ( R ~ 1.4-1.8), despite the weak narrow Fe emission, and a low high-energy cutoff ( E _cut ∼ 60-80 keV, kT _e = 15-20 keV, depending on the model adopted). Most notably, we detect two significant absorption features (at confidence levels of 96.7% and 98.9%, respectively) at ∼7.5 and ∼10 keV in the rest-frame, interpreted as a blueshifted blend of Fe XXV He α and Fe XXVI Ly α . These features indicate the presence of two kinematic components of a highly ionized, high-column ultrafast outflow (UFO) with a velocity of v _out ∼ 0.1 c and v _out ∼ 0.3 c , respectively. The slower wind is consistently detected in an archival 2017 XMM-Newton observation, whereas the faster wind is detected only in 2024. This stratified and variable wind exhibits extreme energetics, with a mass outflow rate of M _out ∼ 20 M _⊙ /yr (corresponding to 15% M _acc ) for each component, and a kinetic power on the order of ∼1 and ∼10% of the bolometric luminosity, respectively. While this represents one of the most powerful UFOs ever detected, its kinetic power is a similar fraction of the QSO’s bolometric luminosity compared to lower-redshift active galactic nuclei. We present several theoretical frameworks to explain the peculiar accretion and ejection properties of this remarkable QSO at cosmic noon.

We report the discovery of 31 new high- z quasars in the redshift range 6.6 < z < 7.8. These quasars were selected from approximately 3000 deg ² of sky covered during the first 1.5 years of the Euclid Wide Survey, representing the initial results of the Euclid high- z quasar search. Our candidate selection employed multiple machine-learning and probabilistic techniques applied to the EuclidI _E , Y _E , J _E , and H _E images, supplemented by ancillary z -band data when available. Spectroscopic follow-up observations were carried out with Keck, Magellan, and the Large Binocular Telescope (LBT). Among the new discoveries, there are 12 quasars at z ≥ 7, more than doubling the number of previously known quasars at z ≥ 7. The newly discovered quasars exhibit 21.2 < J _E < 23.2 (−25.5 < M ₁₄₅₀ < −23.6), extending quasar studies to the faint end of the quasar luminosity function (QLF) at z ≳ 7. The quasar with the highest- z , EUCL J172902.75+641018.1 at z ≈ 7.77, sets the new redshift record for the most distant quasar ever reported. These discoveries demonstrate Euclid ’s transformative role in high- z quasar discovery and set the stage for future follow-up studies of the early galaxies hosting quasars, supermassive black hole growth, and the intergalactic medium in the epoch of reionisation.

The slitless spectroscopy mode of the on board the Euclid telescope has enabled efficient spectroscopy of objects within a large field of view. Nevertheless, the relatively low spectral resolution, overlapping spectra, and contamination pose challenges to source classification and redshift determination using the spectra alone. In this work, we present a large and homogeneous sample of bright quasars identified from the Euclid Quick Data Release (Q1), constructed by combining high-purity candidate selections from to wavelengths without telluric lines, which will be pivotal to quasar spectral analysis. We obtained an empirical spectroscopic depth of JE łesssim 21.5 and ̋E łesssim 21.3 at the sensitivity of the Wide Field Survey, beyond which the number of securely identified quasars declines sharply. Accordingly, the sample presented in this paper comprises spectroscopically confirmed quasars brighter than these limits. We analysed morphological parameters from the Visible Camera (VIS) using Sérsic and model-independent (CAS) metrics, and a deep-learning point spread function fraction to track nuclear dominance. The VIS morphologies show a clear redshift dependence: at low redshift (z<0.5), obvious host structures are common and a single Sérsic model fits about half of the sources; at intermediate redshift (0.5<z<2), the nuclear component dominates, with 90% of the Sérsic fits saturating at the upper index limit. In this intermediate redshift regime, f_ nisp nisp and WISE with the new spectroscopic capabilities of Euclid. Through visual inspection of the Euclid spectra of these quasar candidates, we identify approximately 3500 quasars and determine reliable redshifts in the range of 0< z łesssim4.8. Of these, 2686 are new spectroscopic identifications relative to existing public compilations. We generated the first Euclid composite spectrum of quasars covering rest-frame nuv nir nir PSF is available, and we use it as a more reliable compactness measure than the single-Sérsic and CAS parameters to quantify nuclear versus host emission. We also explore the novel Euclid colour space and discuss the role of these quasars in refining active galactic nucleus selection techniques for future Euclid data releases. nir

We report the discovery of an extremely high-velocity outflow (EHVO) in the most luminous QSO ( L _Bol ∼ 2.29 × 10 ⁴⁸ erg/s), named SMSS J2157-3602, at z = 4.692. Combined XSHOOTER and NIRES observations reveal that the EHVO reaches a maximum velocity of v _max ∼ 0.13 c and persists over rest-frame timescales of a few months up to one year. SMSS J2157-3602 also exhibits one of the highest balnicity index values discovered for an EHVO so far. In addition, the blueshifted CIV emission traces a high-velocity ( v _CIV ⁵⁰ ∼ 4660 km/s) outflow from the broad-line region (BLR). Thanks to an XMM-Newton observation, we were also able to reveal the X-ray weak nature of this QSO, which likely prevents the overionization of the innermost disk atmosphere and facilitates the efficient launch of the detected EHVO and BLR winds. The extraordinary luminosity of SMSS J2157-3602 and the extreme velocity of the EHVO make it a unique laboratory for testing active galactic nucleus (AGN) driven feedback under extreme conditions. Current uncertainties on the outflow’s location and column density strengthen the case for a dedicated follow-up, which will be essential to assess the full feedback potential of this remarkable quasar.

Aims. We aim to characterize the X-ray-to-optical/near-infrared(NIR) broad-band emission of luminous quasars (QSOs) in the first gigayear (Gyr) of cosmic evolution in order to decipher whether or not they exhibit differences compared to the lower-z QSO population. Our goal is also to provide a reliable and uniform catalog of derivable properties for these objects (from fitting their spectral energy distribution), such as bolometric and monochromatic luminosities, Eddington ratios, dust extinction, and the strength of the hot dust emission. Methods. We gathered all available photometry –from XMM-Newton proprietary data in X-rays to rest-frame NIR wavelengths– for the 18 QSOs in the HYPERION samples (6.0 ≤ z ≤ 7.5). For sources lacking uniform NIR coverage, we conducted NIR observations in the J, H, and K bands. To increase the statistical robustness of our analysis across the UV-to-NIR region, we add 36 additional sources to our sample from the E-XQR-30 sample with 5.7 ≲ z ≲ 6.6. We characterized the X-ray/UV emission of each QSO using average SEDs from luminous Type 1 sources and calculated bolometric and monochromatic luminosities. Finally, we constructed a mean SED extending from the X-rays to the NIR bands. Results. We find that the UV-optical emission of these QSOs can be modeled with templates of z ∼ 2 luminous QSOs. We observe that the bolometric luminosities derived while adopting some bolometric corrections at 3000 Å (BC_3000 Å) largely used in the literature are slightly overestimated, by 0.13 dex, as they also include reprocessed IR emission. We estimate a revised value of BC_3000 Å = 3.3, which can be used to derive L_bol in z ≥ 6 QSOs. We provide a subsample of 11 QSOs with rest-frame NIR photometry; these show a broad range of hot dust emission strength, with two sources exhibiting low levels of emission. Despite potential observational biases arising from nonuniform photometric coverage and selection biases, we produce an X-ray-to-NIR mean SED for QSOs at z ≳ 6 that is a good match to templates of lower-redshift, luminous QSOs up to the UV–optical range, with a slightly enhanced contribution from hot dust in the NIR.

One of the main open questions in the field of luminous (L_bol > 10⁴⁷ erg s⁻¹) quasars (QSOs) at z ≳ 6 is the rapid formation (< 1 Gyr) of their supermassive black holes (SMBHs). For this work we analysed the relation between the X-ray properties and other properties describing the physics and growth of both the accretion disc and the SMBH in QSOs at the Epoch of Reionization (EoR). The sample consists of 21 z > 6 QSOs, which includes 16 sources from the rapidly grown QSOs from the HYPERION sample and five other luminous QSOs with available high-quality archival X-ray data. We discovered a strong and statistically significant (> 3σ) relation between the X-ray continuum photon index (Γ) and the C IV disc wind velocity (v_C․IV) in z > 6 luminous QSOs, whereby the higher the v_C․IV, the steeper the Γ. This relation suggests a link between the disc–corona configuration and the kinematics of disc winds. Furthermore, we find evidence at > 2 − 3σ level that Γ and v_C․IV are correlated to the growth rate history of the SMBH. Although additional data are needed to confirm it, this result may suggest that, in luminous z > 6 QSOs, the SMBH predominantly grows via fast accretion rather than via initial high seed BH mass.