Luca Zappacosta

We investigate the multiphase circumgalactic medium during the epoch of reionization ( z > 6) by cross-correlating cool- C II and warm-ionized C IV absorption systems with star-forming [O III ] emitters. JWST/NIRCam wide-field slitless spectroscopy from the EIGER survey was combined with medium- and high-resolution optical and NIR spectra of six background quasars, including new VLT/X-Shooter observations of PSO J159-02. We analyzed the relation between 16 C II and 14 C IV absorbers (log( N ) > 13.0) and 136 galaxies within an impact parameter of R _⊥ ≤ 1000 pkpc and a line-of-sight separation of Δ v ≤ 500 km s ⁻¹ . We detected a statistically significant excess of both ions around galaxies compared to a randomized background. The C IV covering fraction remains enhanced up to ∼1 pMpc, whereas C II drops to the background level beyond ∼0.5 pMpc, demonstrating that the warm-ionized phase is more spatially extended than cooler gas. Jointly, the 3D galaxy-absorber spatial clustering is significantly weaker than the galaxy-galaxy autocorrelation. This provides direct physical evidence that early carbon enrichment is not confined to the virial radius of massive star-forming systems; rather, a substantial fraction of these metals permeates the diffuse intergalactic medium or is injected by a widespread population of faint undetected dwarf galaxies. Finally, we note a rapid radial decline of the C IV covering fraction compared with lower-redshift samples at z < 2 and z ∼ 3 − 4, which indicates an evolving circumgalactic medium ionization structure where early metals predominantly reside in lower ionization states. In conclusion, we determine a conservative lower limit for the observed carbon mass of M _{C  II +C  IV} ≥ 2.8 × 10 ⁶ M _⊙ within 300 pkpc.

Context . The X-ray emission of active galactic nuclei (AGNs) is commonly interpreted as arising from Comptonisation in a hot corona located above the accretion disc. In many sources, a prominent soft X-ray excess is also observed, often explained within the two-corona scenario, where a warm Comptonising layer produces the soft excess, while a hotter corona generates the hard X-ray continuum. However, the physical properties of these coronal components remain poorly constrained in very luminous quasars. Aims . We investigate the structure and physical properties of the X-ray-emitting coronae in two luminous radio-quiet quasars, PG 1407+265 ( z = 0.94) and RBS 229 ( z = 0.334), and test whether the two-corona scenario provides a consistent description of their broadband spectra. Methods . We performed a broadband spectral analysis combining XMM-Newton EPIC and Optical Monitor data with simultaneous NuSTAR observations and long-term Swift monitoring over months to years. The spectra were modelled using Comptonisation models to characterise the properties of both the warm and hot coronae. Results . Both quasars are X-ray-loud with respect to the standard α _OX – L _UV relation, with PG 1407+265 exhibiting the strongest deviation. Their broadband spectra are well reproduced by a two-corona configuration, consisting of a warm, optically thick Comptonising component that accounts for the soft excess and a hot corona responsible for the hard X-ray continuum. Both sources show high energy cut-offs in the range ∼70–80 keV. RBS 229 exhibits moderate reflection and a weak neutral Fe K α line, whereas no significant reflection features were detected in PG 1407+265. The soft excess is present in both quasars, but displays a markedly different behaviour for each: the warm-corona parameters in RBS 229 remain consistent across epochs, while PG 1407+265 displays strong variability, producing an extreme soft-excess episode extending up to ∼3 keV in the rest frame. Conclusions . These results provide new constraints on the properties of AGN coronae in the high-luminosity regime, which remains relatively poorly explored in observations. Both quasars show high energy cut-offs that are broadly consistent with the trends observed in terms of luminosity and accretion rates among AGN samples and safely below the runaway pair-production limit. No clear dependence of the warm-corona properties on the luminosity or the accretion rate was found, as both quasars show similar kT, τ , and soft-excess strengths despite their different regimes, with variations seen mainly in terms of the spectral slope and variability. The strong variability of the warm component in PG 1407+265, compared to the stability of RBS 229, supports a scenario in which the warm corona responds to accretion-flow changes, while remaining within a narrow range of physical conditions.

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.

While the warm ( T ∼ 10 ⁴ K), ionized gas in the circumgalactic medium (CGM) at z > 3 is now routinely observed around bright quasars in Ly α emission, little is known about the CGM hot phase ( T ∼ 10 ⁷ K). Here, we report the analysis of 634 ks of Chandra X-ray observations in the MQN01 Cosmic Structure, a region containing one of the brightest Ly α nebulae and the largest galaxy overdensity known at z > 3. We detect ≈66 net counts (≈8 σ ) of X-ray emission in the 0.5–2 keV band extending to at least ∼30 kpc from the brightest quasar in MQN01. The morphology and spectrum are consistent with thermal emission from hot plasma in collisional ionization equilibrium. Quasi-stellar object (QSO) photoionization is found to have a negligible impact, and alternative scenarios such as inverse Compton scattering are disfavoured. A joint spatial and spectral Markov chain Monte Carlo (MCMC) analysis provides consistency with a β model with a steep density profile ( β ≃ 2.0 ^+1.4 _−0.8 , r _core = 36 ⁺¹³ ₋₁₆ kpc) and an average gas temperature of kT ≃ (1.8 ± 0.4) keV. Assuming that the QSO resides within a virialized halo, whose virial temperature is equal to the observed gas temperature, the implied halo mass and virial radius would be M _vir ∼ 3 × 10 ¹³ M _⊙ and ∼190 kpc. Further assuming that the observed emission traces the brighter inner region of a distribution extending to the virial radius, the extrapolated hot gas mass would be M _hot ≈ 2.6 ^+1.7 _−0.6 × 10 ¹² M _⊙ , which is ≃ 8.3 ^+3.0 _−9.8 % of M _vir , or 56 ⁺⁶⁵ ₋₂₀ % of the theoretical cosmological baryon budget of the halo. The hot gas also emits an exceptionally high X-ray luminosity, with a measured L _2 − 10 = 2.25 _−1.38 ^+0.77 × 10 ⁴⁵ erg s ⁻¹ within the central 30 kpc. This system is a clear outlier in the L _X – T _X plane, indicating a thermodynamic state distinct from that of evolved lower-redshift hot halos. The cooling time in the inner 15-30 kpc is comparable to the local dynamical time (1 < t _cool / t _ff < 10), suggesting that the gas could become locally unstable in the absence of heating or feedback. Moreover, the thermal pressure associated with the detected CGM hot phase is large enough to confine the cold and dense clumps, which are required to reproduce the high Ly α emission associated with the inner regions of the MQN01 structure. Although limited to a single system, our results provide unique information on the multi-phase properties of the CGM (or proto-intracluster medium) and a view of the nascent thermal hot gas phase observed in local galaxy clusters.

Context. NGC 1068 has long served as the reference Compton-thick Seyfert 2 galaxy. Decades of X-ray observations have established the presence of both neutral reflection and ionized circumnuclear emission. However, the limited spectral capabilities of previous CCD and grating data in the Fe–K band have prevented a clean separation of these components, thus leaving large uncertainties on key properties, such as the optical depth, structure, and kinematics of the reprocessing and emitting regions, and on their connection to nuclear outflows and feedback. Aims. We exploited high-resolution X-ray spectroscopy to disentangle the neutral and ionized iron emission in NGC 1068; constrained the physical properties of the cold reflector through line energies, widths, fluorescence ratios, and Compton-shoulder diagnostics; and investigated the origin, kinematics, and potential feedback role of the highly ionized Fe XXV and Fe XXVI emission. Methods. We analyzed an XRISM/Resolve observation of NGC 1068, focusing on the Fe K α and Fe K β fluorescent lines and on the Fe XXV and Fe XXVI emission complexes. Line centroid energies, intrinsic widths, flux ratios, and constraints on the Compton shoulder were derived through local spectral fitting, and compared with atomic calculations and theoretical predictions. Results. The centroid energies of the Fe K α and Fe K β lines tightly constrain the emitting material to be neutral or near neutral. The observed Fe K β /K α ratio, together with the stringent upper limit on the Compton shoulder (≲8−11% of the core flux), disfavor reflection dominated by a homogeneous classical Compton-thick medium, indicating that most of the neutral Fe K α emission arises in optically thin or moderately Compton-thick gas. The Fe XXV and Fe XXVI emission lines exhibit remarkably large velocity widths, of several thousand km s ⁻¹ . These broad profiles closely resemble the integrated optical and infrared [O III ] and [O IV ] lines associated with the large-scale biconical outflow, and are naturally interpreted as the X-ray signature of a more highly ionized, faster, and more spatially confined phase of the same outflow. Conclusions. The iron-K emission of NGC 1068 reveals a stratified circumnuclear environment in which neutral and highly ionized components arise in physically distinct regions. The neutral Fe K fluorescence originates predominantly in optically thin or mildly Compton-thick material, despite the persistently Compton-thick line-of-sight obscuration, indicating a geometrically complex cold reprocessor. The highly ionized iron emission lines trace a fast component consistent with a bipolar outflow on parsec scales, whose large velocities and inferred energetics suggest that it may represent an efficient channel for feedback. If similar ionized outflows and reflection geometries are common in heavily obscured Seyferts, they may constitute an underappreciated aspect of feedback and circumnuclear structure in this class of sources.

We present the X-ray analysis of coronal properties in a statistically representative sample of 23 mostly radio-quiet active galactic nuclei (AGN) from the SUpermassive Black holes Winds in X-rAYs campaign (SUBWAYS), focusing on quasars at redshifts 0.1<z<0.4 and bolometric luminosities 2 <L_ 44 bol ( erg/s)<2 . The main aim of this work is to investigate the properties of the hot corona through the study of the hard X-ray band emission, including a proper treatment of the soft X-ray band. High-quality X-ray spectra from 46 complemented by νstar data extending up to 30–40 keV in the rest frame, are available for this sample. The soft X-ray band (0.3–2 keV) spectrum is best fit by a warm corona model with a median temperature of sim0.40 keV, and an optical depth in the range τ consistent with previous results on lower-luminosity sources. The hard X-ray band is well described using a hot corona model, with a median high-energy cutoff of sim87 keV; 11 out of 23 of the sources have well constrained values at the lower end of the distribution of typical values found in Seyfert galaxies (sim100-200 keV). The derived median value of the optical depth (τ∼ 1-5) suggests the presence of a moderately optically thick corona. By combining the SUBWAYS results with literature samples at low and high redshifts, we assembled the largest sample to date of AGN with E_cut and accretion parameter measurements, finding a significant anticorrelation of E_cut with both λ_̊m Edd and łbol, with the median E_cut decreasing from sim250-300 keV at low accretion rates and luminosities to sim90-100 keV at high accretion rates and luminosities; this is consistent with increased coronal cooling, possibly driven by pair production. These results favor cooler, optically thicker coronae in luminous AGN compared to those in lower-luminosity Seyfert galaxies.

Context. Ultra-fast outflows (UFOs) are highly ionized, mildly relativistic winds seen in the X-ray spectra of active galactic nuclei (AGNs) and are thought to influence AGN feedback and galaxy evolution. Aims. In this work, we aim to investigate the UFO signatures by analyzing a large and diverse sample of detections from the literature. Methods. We compiled a sample of 122 solid (> 2 σ c.l.) UFO detections for a total of 57 AGNs, spanning broad ranges in redshift ( z ≲ 4), bolometric luminosity (10 ⁴³ ≲ L _bol ≲ 10 ⁴⁹ erg s ⁻¹ ), black hole mass (10 ⁶ ≲ M _BH / M _⊙ ≲ 10 ¹⁰ ), and Eddington ratio (−2.7 ≲ log λ _Edd ≲ 0.6). We combined results from both phenomenological and photoionization modeling of the absorption features to characterize correlations among UFO parameters. Results. We find evidence for a positive correlation between the line width σ , the equivalent width EW, and the outflow velocity υ _out , with the υ _out − σ trend being comparatively weak. This suggests that the broadest absorption lines with the largest EW are signatures of the fastest UFOs. We further demonstrate that the inferred velocity dispersion, often much larger than the uncertainty on the centroid velocity, should be accounted for in studies of wind energetics and scaling relations. We estimate lower limits on the launching radii of UFOs finding a minimum distance consistent with the innermost stable circular orbit (ISCO) of a weakly or non-rotating Schwarzschild black hole. This apparent truncation at smaller radii may reflect physical constraints, such as the presence of the X-ray corona or observational limitations due to line broadening. Additionally, variations in the line width to velocity ratio imply differences in wind geometry and kinematics. For the first time, we also explore the dependence of UFOs on AGN class. Differences in UFO properties between Seyferts and quasars – bridged by narrow-line Seyfert 1 galaxies – are likely driven by intrinsic parameters such as black hole mass and luminosity. Conclusions. The observed co-variation of υ _out with both σ and EW is consistent with clumpy, multi-component winds propagating through a thermally unstable multiphase medium within the chaotic cold accretion (CCA) cycle. These trends are not unique to a single acceleration mechanism: MHD and line-driven winds remain viable. High-resolution spectroscopy from missions like XRISM and NewAthena is necessary to fully resolve the structure, kinematics, and physical origin of UFOs.

Context. The most luminous and obscured quasars (QSOs) detected through sensitive infrared all-sky surveys are thought to represent a key co-evolutionary phase from nuclear to circumgalactic (CG) scales in the formation of massive galaxies. In this context, hot dust obscured galaxies (hot DOGs) in the redshift interval z ∼ 2 − 4 (the so-called cosmic noon) provide unique opportunities to investigate the relation between cosmic mass assembly and the nuclear accretion processes of luminous QSOs and galaxies at high- z . W0410−0913 (hereafter W0410−09) is a luminous ( L _bol ∼ 6.4 × 10 ⁴⁷ erg s ⁻¹ ) and obscured QSO at z = 3.631 that is characterized by a 30 kpc CG Ly α nebula (CGLAN), which is rather small when the ∼ 100 kpc Ly α nebulae around the unobscured QSO is compared to the Type I QSO peers, and by an exceptional overdense environment of Ly α emitters (LAEs), with ∼19 of them located in the CG region with a radius of 300 kpc at a distance of ±200 km s ⁻¹ from the Hot DOG. Aims. Our aim is to detect and characterize active nuclear accretion in the Hot DOG W0410−09 and its environment. Methods. We carried out this study by exploiting a deep proprietary ∼280 ks Chandra X-ray Observatory observation. We employed a set of empirical models suited for obscured sources and physically motivated spectroscopic models to account for a toroidal X-ray obscurer and the reprocessing of the X-ray radiation. Results. The source W0410−09 consistently exhibits nuclear obscuration levels from mild to high star formation; it is Compton-thick (CT) and has a hydrogen column density of N _H > 10 ²⁴ cm ⁻² (and up to N _H ∼ 10 ²⁵ cm ⁻² ) and an intrinsic luminosity of L _2 − 10 > 10 ⁴⁵ erg s ⁻¹ . W0410−09 is therefore one of the most luminous and obscured QSO at z > 3.5 discovered so far. This level of obscuration and the highly accreting nature of the Hot DOGs suggest that W0410−09 is undergoing a blow-out phase. This phase is predicted by models of merger-driven QSO formation scenarios, where strong winds begin to clear the dusty obscuring medium from the nuclear surroundings. We speculate that this heavy nuclear obscuration limits the amount of UV disk emission that powers its CGLAN, which in turn likely explains its small nebula size. Except for W0410−09, we detected no X-ray emission from any of the 19 LAEs. We analyzed their combined emission in several bands and only found a significant signal at the 3 σ level in the 6−7 keV rest-frame energy band. We interpret this as caused by the Fe K α line. This strongly suggests heavily obscured but so far undetected active galactic nuclei (AGN) emission in several LAEs. Considering W0410−09, we estimate an AGN fraction of f _AGN ^LAE = 5 ₋₄ ⁺¹² %. This value can reach ∼35% when we account for unresolved obscured AGN, as suggested by the detection of the Fe K α line. Conclusions. W0410−09 is powered by an intrinsically luminous CT quasar. Its high obscuration likely explains the limited extent of its CGLAN. Our analysis suggests that this object is in a crucial transitional blow-out phase, during which powerful QSO-driven outflows will sweep out the nuclear obscuration to pave the way for an unobscured bright quasar.

We present James Webb Space Telescope (JWST)/NIRSpec PRISM spectroscopic characterization of GHZ9 at z = 10.145 ± 0.010, currently the most distant source detected by the Chandra X-ray Observatory. The spectrum reveals several UV high-ionization lines, including C II, Si IV, N IV], C IV, He II, O III], N III], and C III]. The prominent rest-frame equivalent widths (EW(C IV) ≃ 65 Å, EW(O III]) ≃ 28 Å, and EW(C III]) ≃ 48 Å) show the presence of a hard active galactic nucleus (AGN) radiation field, while line ratio diagnostics are consistent with either AGN or star formation as the dominant ionizing source. GHZ9 is nitrogen-enriched (6–9.5 (N/O)_⊙), carbon-poor (0.2–0.65 (C/O)_⊙), metal-poor (Z = 0.01–0.1 Z _⊙), and compact (0.02, implies an accelerated growth of the BH mass with respect to the stellar mass. GHZ9 is the ideal target to constrain the early phases of AGN–galaxy coevolution with future multifrequency observations.