Cosimo Marconcini

The study of starburst- and active galactic nucleus (AGN)-driven feedback is fundamental for understanding the processes that shape galaxy growth, quench star formation, and drive the co-evolution of galaxies and their central black holes. We present a spatially resolved study of six galaxies at 3 < z < 9, including starburst- and AGN-dominated systems, observed with the JWST/NIRSpec Integral Field Unit in low- ( R ∼ 100) and high-resolution ( R ∼ 2700) mode. Previous analyses of R ∼ 2700 data revealed ionized outflows in all these galaxies. We explored possible links between outflows and stellar population properties to assess the mechanisms driving galaxy evolution at early epochs. We derived stellar masses and star formation histories (SFHs) using the spectral energy distribution fitting code Prospector , applied to both single spaxels and spatially integrated spectra, exploring parametric and non-parametric SFHs. We find that unresolved stellar mass measurements are systematically underestimated, with discrepancies increasing towards higher sSFRs (up to ∼0.75 dex), consistent with the so-called outshining effect. Combining the spatially resolved stellar population analysis with the outflow properties, we find that the most massive galaxies ( M _★ > 5 × 10 ¹⁰ M _⊙ ) with strong AGN-driven ionized outflows show evidence of past quenching episodes occurring within the last ∼100 − 300 Myr, mainly in the nuclear regions ( r < 3 kpc). In contrast, higher-redshift ( z > 5) and less massive ( M _★ < 10 ¹⁰ M _⊙ ) starburst galaxies with powerful (starburst-driven) outflows appear to have experienced continuous growth, with no clear sign of quenching. Massive galaxies with weaker outflows do not show evidence of quenching in their history. One massive AGN host (GS20936) shows evidence of a recent (10−30 Myr) rejuvenation phase, likely fuelled by a recent major merger. This interpretation is supported by TNG300 cosmological simulations, which indicate that ∼5% of galaxies with M _★ > 5 × 10 ¹⁰ M _⊙ undergo similar rejuvenation events driven by merging at z ∼ 3. These results suggest that (AGN-driven) outflows can already play a key role in shaping the SFHs of massive galaxies at early cosmic epochs, while also highlighting the importance of spatially resolved analyses for accurately reconstructing their evolutionary pathways.

Since its launch, JWST has enabled the characterisation of the ionised interstellar medium (ISM) of high-redshift galaxies using a range of rest-frame ultraviolet (UV) and optical diagnostics originally developed in the Local Universe. These observations challenge the validity of such classical methods in extreme high-redshift environments. We present an analysis of the ISM in three case studies at z = 2–6 (MARTA-4327, the Sunburst Arc, and RXCJ2248-ID) using the multi-cloud photoionisation modelling framework HOMERUN, which models integrated galaxy spectra as linear combinations of photoionised regions spanning a wide range of ionisation parameter and density conditions. We show that emission from unresolved high-density ( n _e = 10 ⁴ –10 ⁷ cm ⁻³ ) regions boosts temperature-sensitive line ratios, but it shows a weak impact on standard optical density tracers. If this density-ionisation structure is not properly constrained, gas temperatures are biased high and the derived T _e -method metallicities are underestimated by ∼0.15–0.3 dex, as we found for MARTA-4327. We modelled the rest-frame UV and optical data simultaneously to interpret the observed discrepancies between N/O estimates derived from UV and optical emission lines. In RXCJ2248-ID, the disagreement can arise naturally from ionisation and density effects alone. In contrast, the Sunburst Arc shows evidence of chemical stratification, with a nitrogen-enriched matter-bounded component coexisting with a chemically normal ionisation-bounded one. Finally, high-ionisation lines such as He II λ 1640 and C IV λλ 1548,1551 could be explained within a pure star-formation scenario that invokes matter-bounded regions, consistent with non-negligible Lyman-continuum leakage. However, in the case of RXCJ2248-ID, we cannot rule out a minor contribution from an active galactic nucleus based solely on the observed emission-line fluxes. These results show that classical diagnostics can be significantly biased in high-redshift galaxies and highlight the need for self-consistent approaches to interpret the complex ISM conditions and chemical enrichment in the early Universe.

We present new JWST/MIRI integral field spectroscopy (IFS) observations of the prototypical Seyfert 2 galaxy NGC 1068. These observations, combined with archival VLT/MUSE data, allow us to investigate the outflow from the active galactic nucleus (AGN) and radio jet and its interaction with the circumnuclear multiphase gas. MIRI data trace the ionized and warm molecular gas emission up to ∼ 400 pc from the nucleus at 20--60 pc spatial resolution, unveiling a clumpy ionized structure surrounding the radio hot-spots and a rotating warm molecular disk. Mid-infrared (mid-IR) and optical diagnostic diagrams show that AGN photoionization dominates across the entire MIRI field of view, with no evidence of star formation excitation, supporting the scenario of an AGN-driven wind. Density sensitive mid-IR transitions reveal compact high-density clumps (n_̊m e ge 10 4 $ cm^-3) along the outflow edges, consistent with gas compression by the expanding wind. Combining multi-cloud kinematic ( and photo-ionization (HOMERUN) modeling, we identify two distinct ionized outflow components: a dust-poor component dominating the optical line emission and a dust-rich component responsible for the mid-IR high-ionization emission. The latter traces gas that is ∼300 ̨ms faster than the optical component and carries most of the ionized mass, demonstrating that a large fraction of the outflow is hidden from classical optical diagnostics. Kinematic and photoionization models consistently point to a two-stage acceleration scenario, with velocities reaching ∼2000 ̨ms, consistent with an energy-driven wind. Our multi-cloud modeling indicates that the outflow entrains up to a few 10$^ 6 of ionized gas and couples efficiently with the surrounding interstellar medium, injecting substantial turbulence and strongly impacting the host-galaxy environment.

We present VLT/ERIS integral field unit (IFU) J -band observations of MCG-03-34-64, a nearby ( z = 0.0167) Seyfert galaxy hosting a candidate dual active galactic nucleus (AGN) system with a separation of ∼100 pc between the nuclei, which are detected in Fe-K α X-ray images and [O III ] λ 5007Å narrow-band images. The ERIS observations cover, among others, the He I λ 1.083μm, [Fe II ] λ 1.257μm, and Pa β emission lines, over a field of view of 3″ × 3″ (∼1 × 1 kpc ² ). We analysed the ionised gas kinematics and identified two regions with an enhanced velocity dispersion ( W 80 ∼ 1500 km s ⁻¹ ), which is suggestive of fast outflowing gas, spatially coincident with the position of the two candidate active nuclei. We extracted the spectra from the two regions and used them to derive the properties of the ionised outflows. The two spectra show a prominent blueshifted wing with velocities v _max ∼ −1700 km s ⁻¹ , which corresponds to the highest 2 − 5 percentiles of samples of local AGN with similar bolometric luminosities (∼10 ⁴⁴ erg s ⁻¹ ). For the ionised phase of the two outflows, we derive comparable masses of ∼(4 ± 1)×10 ⁵ M _⊙ and mass outflow rates of ∼20 ± 5 M _⊙ yr ⁻¹ . The two distinct outflows could be associated with the two nuclei or be generated by the interaction of the radio jet with the interstellar medium (ISM). The map of the [Fe II ]/Pa β line ratio shows the highest values in the more external regions (compatible with shock excitation), intermediate values in the vicinity of the nuclei (compatible with AGN excitation), and lower values between the two nuclei, close to the peak of the optical and near-infrared continuum. We interpret this as due to a contribution to the Pa β emission from a nuclear starburst or to enhanced AGN ionisation. We also analysed the peculiar (very broad, boxy) profile of the [Fe VII ] λ 6087Å optical coronal line from an archival VLT/X-shooter spectrum. The comparison with the [Ne V ] λ 3425Å and [Fe II ] λ 1.257μm profiles indicates that [Fe VII ] emission likely arises only from the outflow. The absence of the systemic component in [Fe VII ] – unlike in [Ne V ], which has similar ionisation potential and critical density – suggests suppression of [Fe VII ] due to iron depletion onto dust grains, while its detection in the outflow implies a lower dust content than in the host ISM. The additional information gained from the ERIS data are consistent with the scenario of a dual AGN, however, further observations are required to confirm its nature.

Recent discoveries of faint active galactic nuclei (AGN) at the redshift frontier have revealed a plethora of broad Hα emitters with optically red continua, named little red dots (LRDs) ¹ , which comprise 15–30% of the high-redshift broad-line AGN population ² . Owing to their peculiar properties ^3–6 , modelling LRDs with standard AGN scenarios has proven challenging. In particular, the validity of single-epoch virial mass estimates in determining the black-hole masses of LRDs has been called into question, with some models claiming that masses might be overestimated by up to two orders of magnitude ^7–10 . Here we report a direct, dynamical black-hole mass measurement in a strongly lensed LRD at a redshift of 7.04. The combination of lensing with deep spectroscopic data reveals a rotation curve that is inconsistent with a nuclear star cluster, yet can be well explained by Keplerian rotation around a point mass of 50 million solar masses, consistent with virial black-hole mass estimates. The Keplerian rotation leaves little room for any stellar component in a host galaxy, as we conservatively infer M _BH / M _⁎ > 2 (where M _BH is the black-hole mass and M _⁎ is the stellar mass). Such a ‘naked’ black hole, together with its near-pristine environment ¹¹ , indicates that this LRD is a massive black-hole seed caught in its earliest accretion phase.

We present the first-year results of the MUSE Large Program “Cosmic Duets”, whose goal is to obtain adaptive-optics assisted MUSE observations with a typical angular resolution of 0.1″ − 0.2″ in order to provide integral-field spectroscopy of sub-arcsec separation dual and lensed active galactic nucleus (AGN) candidates. These observations reveal previously unexplored properties of dual and lensed systems that are key to understanding galaxy evolution, supermassive black hole mergers, and strong-lensing modeling. Targets were efficiently selected using the Gaia multipeak (GMP) technique, which identifies pairs of point-like sources with angular separations below 0.8″ in the Gaia catalog. MUSE spatially resolved spectroscopy provides accurate redshifts, ionization diagnostics, and identification of absorption systems along the line of sight. We report results for 30 GMP-selected targets at z = 0.5 − 3.5. All systems show at least two spatially resolved components. Nineteen objects are confirmed as AGN multiplets, including six dual AGN, ten doubly lensed quasars, and three quadruply lensed systems, while the remaining 11 correspond to chance alignments with foreground stars. Among all the spectroscopically confirmed dual AGN in the literature, 27 pairs have projected separations below 7 kpc in this redshift regime, and our sample accounts for 22% of the total. We studied dual and lensed AGN distributions as a function of redshift, magnitude, and projected separation while accounting for selection effects, and we find that bright systems ( J ≲ 16.5) are dominated by lensed quasars, whereas the relative fraction of dual AGN increases at fainter magnitudes. This first-year sample demonstrates the high efficiency of GMP preselection combined with MUSE spectroscopy for identifying sub-arcsec dual and lensed AGN. The full program, targeting ∼150 systems, will enable statistical studies of dual AGN incidence as a function of redshift, separation, and luminosity and allow for precise characterization of the mass composition and distribution in strong lensing galaxies.

We present a comprehensive analysis of the nitrogen-to-oxygen (N/O) abundance ratio in a sample of ∼660 star-forming galaxies at redshift z ∼ 1 − 6, with a median redshift of ⟨ z ⟩ = 3.0, using deep JWST/NIRSpec spectroscopy. Leveraging detections of faint auroral emission lines in 92 galaxies at z > 1 from both the MARTA survey and a large compilation of high-redshift literature objects, we derived direct electron-temperature-based abundances for nitrogen and oxygen using rest-frame optical lines. We establish the first high-redshift calibrations of strong-line N/O diagnostics based on ‘direct’ abundance measurements, finding a mild evolution for the N2O2 = log([N II ] λ 6585/[O II ] λλ 3727,3729) diagnostic and no clear evolution for the N2S2 = log([N II ] λ 6585/[S II ] λλ 6717,6731) diagnostic compared to local realisations. We then investigated the N/O–O/H relation across cosmic time using both ‘direct’ abundances and strong-line-based measurements (additional 535 galaxies). We find evidence of mild but systematic nitrogen enhancement at high redshift: galaxies at z > 1 exhibit N/O ratios elevated by ∼0.18 dex (median offset) at fixed O/H compared to local trends, with a more pronounced enhancement at low metallicity (i.e. 12 + log(O/H)≲8.1), where the offset reaches up to ∼0.4−0.5 dex. We considered several scenarios to explain the observed trends, including bursty star formation, differential metal loading, and inflows of pristine gas. Our results provide the most extensive confirmation of elevated N/O ratios at high-redshift to date based on rest-optical diagnostics and within a self-consistent frame.

We present a multiphase analysis of the gas in the circumnuclear region (∼0.9 × 0.9 kpc ² ) of the nearby barred Seyfert 1.8 galaxy NGC 1365, observed as part of the Mid-IR Activity of Circumnuclear Line Emission (MIRACLE) program. Specifically, we combined spatially resolved spectroscopic data from JWST/MIRI, VLT/MUSE, and ALMA to provide a multiphase characterization of the ionized atomic and the warm and cold molecular gas phases. MIRI data enabled the detection of more than 40 mid-IR emission lines from ionized or warm molecular gas. Moment maps show that both cold and warm molecular gas trace the circumnuclear ring, following the rotation of the stellar disk. The ionized gas exhibits flux distributions and kinematics that vary depending on the ionization potential (IP). Low-IP species (≤25 eV) mainly trace the rotating disk, while higher-IP species (up to ∼120 eV) trace the outflowing gas. Both [O III ] λ 5007 Å and [Ne V ] λ 14 μm trace the nuclear outflow cone toward the southeast. In addition, the [Ne V ] λ 14 μm line traces the counter-cone of the outflow to the northwest, which is obscured in the optical at these circumnuclear scales, and is thus undetected in [O III ] λ 5007 Å. Unlike optical diagnostics, spatially resolved mid-IR diagnostics reveal the key role of the active galactic nucleus (AGN) as the source of gas ionization in the central region. We derived the electron density from the [Ne V ] λ 24 μm/[Ne V ] λ 14 μm line ratio, finding a median value of (750 ± 440) cm ⁻³ , consistent with previous estimates obtained from the optical [S II ] doublet. Lastly, we applied, for the first time, a fully self-consistent combination of state-of-the-art photoionization and kinematic models (HOMERUN + MOKA ^3D ) to estimate the intrinsic physical outflow properties, kinematics, and energetics – overcoming the limitations of classical methods based on oversimplified assumptions. Exploiting the unprecedented synergy between JWST/MIRI and VLT/MUSE, HOMERUN allows us to simultaneously reproduce the fluxes of over 60 emission lines spanning from the optical to the mid-IR. This unique approach enables us to disentangle the physical conditions of AGN- and star formation-dominated components and robustly estimate the mass of the outflowing gas and other physical properties.