Martina Scialpi

Context. Dual active galactic nuclei (DAGN) – systems of two simultaneously accreting supermassive black holes at kiloparsec-scale separations – are critical tracers of galaxy mergers and the progenitors of gravitational-wave sources targeted by pulsar timing arrays and the upcoming Laser Interferometer Space Antenna. Despite their importance, their radio properties remain largely unconstrained, particularly at high redshift, due to the limited combination of sensitivity and sky coverage of existing high-angular-resolution surveys. Aims. In this pilot project, we primarily aim to demonstrate the detectability of high-redshift DAGN at 144 MHz performing subarcsecond resolution imaging of the LOFAR Two-metre Sky Survey (LoTSS) data, and characterize the low-frequency radio properties of individual systems. Methods. We crossmatched a sample of 92 spectroscopically confirmed DAGN at z > 0.3 and projected separation r _p < 30 kpc with the LoTSS catalogs of data release (DR) 2 (resolution ∼ 6″), and reprocessed the international LOFAR telescope (ILT) LoTSS data for three sources spanning 0.59 < z < 2.39, achieving ∼0.3″ resolution at 144 MHz. We performed a multifrequency analysis and brightness temperature diagnostics to characterize the AGN nature and radio properties of each system. Results. We successfully produced high-quality ILT images for the three DAGN in the pilot sample. In one source at z = 1.49, we detected both AGN components at > 5 σ , making it one of the highest- z and faintest DAGN detected at radio frequencies. Brightness temperature measurements confirm that ILT 144 MHz observations can efficiently distinguish AGN-powered emission from star formation even in sub-milliJansky sources. In the other two sources, we detected only one AGN. In one of them, the new ILT imaging constrains the low-frequency radio spectrum of the compact steep spectrum source, indicating that its complex morphology is shaped by jet-interstellar medium interaction rather than by the companion galaxy. In addition, for the full 92 DAGN sample, we found a detection rate of ∼24% in both LoTSS DR2 and DR3, significantly higher than that of single AGN matched in selection (∼9–10%), suggesting an enhanced detectability of DAGN in LoTSS. Conclusions. Low-frequency, subarcsecond-resolution radio observations constitute a highly efficient and dust-unbiased pathway to detect, confirm, and characterize DAGN across cosmic time. The pilot sample presented here establishes the foundation for a systematic DAGN search in the upcoming all-sky ∼0.3″ resolution international LoTSS (ILoTSS) and provides an early benchmark for the future Square Kilometre Array (SKA) observations.

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 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.

We present a study of an X-ray-selected sample of active galactic nuclei (AGN) in pairs at projected spatial separations 1 < r _p /kpc < 100 at z < 0.1, using XMM-Newton and Chandra data. We derived the pair sample from an initial pool of approximately 2000 X-ray-selected AGN, and is composed of both AGN-AGN pairs (so-called dual AGN) and AGN-galaxy pairs. From this selection, we find that approximately 10% of AGN reside in pairs, and about 4% are paired with another AGN. We performed a detailed X-ray and SDSS optical spectral analysis for AGN in dual systems and X-ray analysis for AGN in AGN-galaxy pairs, to characterise their absorption properties and investigate the possible triggering mechanisms. We then investigated how obscuration, luminosity, and Eddington ratio depend on projected separation r _p . Amongst all AGN in pair, we find that ∼55% are obscured (with hydrogen column density N _H > 10 ²² cm ⁻² ), amongst which ∼6% are Compton-thick ( N _H > 10 ²⁴ cm ⁻² ). The fraction of absorbed AGN is significantly higher in late-stage mergers ( r _p < 30 kpc) compared to early-stage mergers ( r _p > 60 kpc). Amongst the AGN pairs, we also observe an average excess relative to a control sample of inactive galaxies in pairs, and this excess significantly increases with decreasing r _p , but only for obscured AGN. Finally, in dual-AGN systems, both the bolometric luminosity and the Eddington ratio of the less massive black hole in the pair increase as the separation decreases. These findings suggest that mergers may play an important role in triggering AGN accretion and activity.

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.

Cosmic noon represents the prime epoch where today's massive galaxies assembled most of their stellar masses, and it is an ideal period for observations with both the space-based (JWST) and ground-based near-IR integral-field unit (IFU) spectrographs. This work analyzes JWST NIRSpec Micro Shutter Array (MSA) and NIRCam Wide Field Slitless Spectroscopy (WFSS) observations of $), and ionization parameter (log(U)≃-3.0). The central bulge is modestly massive (M_⋆=(7±3)times10^9 M_⊙), heavily obscured (A_V=6.43±0.55), and likely formed most of its stellar mass in the past (SFR=82±42 James Webb Telescope a large spiral, star-forming (SF) galaxy at z=2.224 with evidence of radial gas inflows. Leveraging ground-based IFU ERIS observations, we conducted a comprehensive and resolved study of the interstellar medium and stellar properties of this galaxy, covering the rest-frame optical to near-IR. Our analysis -- using several emission-line diagnostics, resolved spectral energy distribution (SED) fitting of high-resolution imaging, and line detection in NIRCam WFSS data -- reveals massive SF clumps (M_⋆≃(0.67-3.5)times10^9 M_⊙) with star formation rates (SFRs) of 3-24 low dust attenuation (A_V≃0.4), electron densities (n_̊m ełesssim300 cm -3 over the last ∼100 Myr). Yet, it continues to form stars at a lower rate (SFR$=12 over the last ∼10 Myr). We infer a relatively low sulfur abundance of log(S/O)≃-1.9, which may have implications for sulfur production via type I supernova explosions. Moreover, all distinct galaxy regions feature a metallicity of 12+log(O/H)≈8.54, likely due -- along with the enhanced N/O abundance (i.e., log(N/O)≃$-1.0) -- to dilution effects from radial inflows of metal-poor gas. Lastly, we find tentative evidence of a negative gradient in stellar age, suggesting possible inside-out growth for

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.