Raffaella Morganti

Context . The brightest cluster galaxy NGC 1275, at the centre of the Perseus cluster, hosts the radio-loud active galactic nucleus (AGN) 3C 84 and a circumnuclear disc (CND) of cold molecular gas. Large-scale molecular filaments traced by CO emission converge towards the nucleus and accrete onto this disc providing a direct observational link between gas cooling from the intracluster medium and the fuelling of the central engine. The physical and chemical conditions of the molecular gas within the CND, and how they are shaped by this accretion process, remain poorly constrained. Aims . We conducted a spatially resolved analysis of the molecular gas conditions across the CND with the aim to determine the radial and azimuthal distributions of the gas density, kinetic temperature, and cosmic ray ionisation rate, and to identify the processes that govern the observed molecular line emission. Methods . We analysed ALMA observations of CO(2–1), HCN(3–2), and HCO ⁺ (3–2) at a resolution of 72 pc. The data were partitioned into beam-sized hexagonal regions and modelled using a Bayesian inference framework that couples a neural network emulator of time-dependent chemistry ( UCLCHEM ) with non-local thermodynamic equilibrium radiative transfer ( SpectralRadex ). For each region, we derived posterior distributions of the gas density, kinetic temperature, and cosmic ray ionisation rate. Bimodal posteriors were identified through Gaussian mixture modelling and validated with posterior predictive checks. Results . All three line ratios peak in the inner disc and decline with radius. The Bayesian analysis shows radial gradients in gas density (log ₁₀ n (H ₂ )≈6.3 to ∼5), kinetic temperature (∼200 K to ∼160 K), and cosmic ray ionisation rate (log ₁₀ ( ζ/ζ ₀ )≈4.9 to ∼3). Despite the powerful radio AGN, the observed HCN(3–2)/HCO ⁺ (3–2) ratio remains ≲1 across the disc; our modelling indicates that this is caused by optical depth saturation of HCN(3–2) ( τ ∼ 1–3), which suppresses the intensity ratio even when the underlying HCN abundance exceeds that of HCO ⁺ by a factor of 3 or more. Azimuthally resolved profiles suggest a localised increase in the HCO ⁺ /CO at the western disc boundary, that coincides with the filament–disc accretion interface. Conclusions . The HCN/HCO ⁺ intensity ratio cannot serve as a direct abundance diagnostic without accounting for optical depth, and a low observed ratio does not necessarily imply a weak AGN influence on the chemistry. The western HCO ⁺ /CO increase is consistent with shock processing driven by velocity shear between the infalling filaments and the rotating disc. These results indicate that the CND is shaped by accretion from the surrounding filamentary environment.

We present JWST MIRI medium-resolution spectrometer (MRS), NIRSpec, NIRCam, and MIRI imaging observations of 3C 305, a radio galaxy with a compact jet that is confined within the galaxy. We utilize the H ₂ 0–0 S(1)–S(7) lines, several mid-infrared (MIR) fine structure lines, and polycyclic aromatic hydrocarbon (PAH) emission in the MIRI MRS spectrum to conduct a multiphase study of the radio jet’s impact on the interstellar medium. Multiple tracers, including H ₂ /PAH 11.3 μ m and [Fe II ] 5.34 μ m, provide evidence for shocks at the jet termination locations. Two Gaussian components are required to reproduce the kinematics of warm H ₂ adequately, with one representing the bulk low-velocity component, while the other corresponds to an outflow. The ionized gas attains higher outflow velocities than the H ₂ outflow. The stark increase in velocities at the jet hotspots points to jet-driven outflows. We fit the H ₂ excitation diagram with a power-law temperature distribution and find that the hotspots exhibit flatter slopes, indicating a larger warm/hot gas mass fraction at these locations. Our MAPPINGS line-ratio analysis indicates that most of the MIR ionized gas can be fit by a “shock+precursor” model. We find that strong radiative losses dominated by line cooling, along with moderate kinetic power of the molecular + ionized gas outflows, can account for all of the estimated jet power, indicating high jet coupling efficiency in 3C 305. Our results, in tandem with other studies on multiphase gas, show that jets efficiently shock-heat and accelerate the gas that comes in contact with them, driving massive, kiloparsec-scale, multiphase outflows.

The presence, distribution and kinematics of atomic neutral hydrogen in the central regions of galaxies can be traced by the H I 21 cm line observed in absorption. Depending only on the strength of the radio continuum, the associated absorption can trace the gas down to pc scale, which is ideal for exploring the H I in the nuclear regions of radio AGN. This paper gives a brief overview of the main recent findings with particular focus on the AGN-driven H I outflows. Absorption has made possible the discovery of fast and massive H I outflows and their clumpy structure on pc scales. The similarities with the predictions of numerical simulations confirm the impact of young radio jets in the feedback cycle and galaxy evolution. The field of H I absorption is rapidly expanding thanks to new “blind” surveys and the increased spectral capabilities of the radio telescopes. This opens many possibilities for future discoveries and complements the studies of H I emission.

The jets and lobes of nearby, extended radio galaxies are ideal laboratories for exploring the spectral and dynamical evolution of the radio emitting plasma that emanates from active galactic nuclei and propagates through the ambient medium. Here, we present a deep, high-resolution radio continuum study of the low-redshift ( z = 0.01713), Fanaroff-Riley class I (FRI) radio galaxy 3C 449 performed with a combination of radio data at 145 MHz acquired with the LOw Frequency ARray (LOFAR) and archival Very Large Array (VLA) data at 1365, 1485, 4985, and 8485 MHz. Our LOFAR maps of the source have angular resolution 20″ × 20″ (7.2 kpc × 7.2 kpc) and 6.0″ × 6.0″ (2.2 kpc × 2.2 kpc), revealing the full extent of the known radio emission (≈22′, i.e. ≈480 kpc) at the highest angular resolution achieved to date. Our spectral index maps show, for the first time, the high-resolution distribution of the spectrum in the 145–8485 MHz frequency range over a source region that extends beyond 2.5′ (54 kpc). The average 145–8485 MHz source spectrum is consistent with a single power law and stays approximately constant over the inner ≈50″ (≈18 kpc) of both source jets. Beyond ≈50″, both on the northern and on the southern source sides, the higher-frequency spectrum steepens and the spectral break frequency lowers with increasing distance from the radio core, indicating the absence of relevant sites of particle acceleration beyond those distances. In our 145–1365 MHz spectral index map, we detected a flatter spectrum spine surrounded by a steeper spectrum sheath in the inner ≈2.5′ (54 kpc) and ≈3′ (65 kpc) of the southern and northern jet, respectively. Beyond ≈1′, the spine-sheath structure was also detected in the 1365–8485 MHz frequency range, confirming previous findings. The steep spectrum sheath may be the signature of interaction between the jet and the ambient medium. By modelling the spectral index maps under the assumption of equipartition and of a constant magnetic field across the source, we derived maps of the highest radiative age of the particles all over the source in a standard ageing scenario. From the oldest radiating plasma, located in the southern radio lobe, we estimated the source spectral age as τ ≃ 200 Myr. At the outer edges of both the northern tail and southern lobe, we estimated a spectral age of τ _sp ≃ 150 Myr. If the latter age were representative of the dynamical source age, the average expansion speed of both jets during the source lifetime would be supersonic, with M ≃ 4.1 and M ≃ 2.8 for the northern and southern jets, respectively. Because numerical magneto-hydrodynamical simulations of FRI jets suggest that the source’s current expansion is subsonic, the high average Mach numbers might arise either from the source being highly supersonic for a small fraction of its lifetime or from a severe underestimation of the spectral age. This is either due to particle acceleration on scales of hundreds of kiloparsecs (not detected in our observations) or to the presence of a non-homogeneous magnetic field with a complex structure.

We present a multi-line study of the kinematics of the molecular and ionised gas phases in the central ∼2 kpc of the luminous infrared galaxy and dual active galactic nucleus (AGN) NGC 6240, based on archival JWST/NIRSpec and ALMA observations. Since a primary goal of our analysis is to study outflows, we devised a new spectral-line fitting approach to de-blend rotating and non-rotating gas components in the observed near-infrared (NIR) emission lines. Our method is more physically motivated than previous approaches and better tailored to the extreme feedback mechanisms at work in NGC 6240. We find that ∼65% of the Pa α , H ₂ , and [FeII] line fluxes within the NIRSpec field of view arise from gas components that are kinematically decoupled from the stars. In particular, the NIR H ₂ lines show the most deviation from the stars, with peak emission between the two rotating stellar structures. The polycyclic aromatic hydrocarbon (PAH) emission feature at 3.3 μm does not follow the NIR H ₂ morphology, indicating that the latter does not trace photon-dominated regions. In the non-rotating gas components, we identified a bi-conical wind that launched from the northern AGN, expanding along the minor axis of stellar rotation. This wind is dominated by ionised gas and, although it entrains some H ₂ gas, it does not show a H ₂ /PAH enhancement, suggesting either high UV irradiation or expansion along a relatively gas-free path. Furthermore, we find bright non-rotating gas emission between the two AGNs and around the southern AGN, which we interpret as due to an outflow that launched from the southern nucleus, coinciding with the massive molecular outflow previously studied in cold (sub-)millimetre tracers. The strong H ₂ /PAH enhancement measured in this region, coextensive with high velocity redshifted gas ( v ∼ 900 km s ⁻¹ ), suggests that the shocks responsible for the high H ₂ /PAH ratios are due to the outflow rather than to the collision of media during the merger. Our results show that most of the NIR line emission in NGC 6240 is decoupled from the stars, and that most of the warm H ₂ is shock-excited and embedded in a powerful outflow, where it coexists with colder molecular gas.

We present the discovery of seven molecular clouds in the radio galaxy B2 0902+34 at redshift z = 3.4. These clouds are detected as CO(0–1) absorption features against the bright radio continuum and spectrally resolved using the Karl G. Jansky Very Large Array. The velocity dispersion of the individual absorption components ranges from 3 to 7 km s ⁻¹ , which is similar to values observed for molecular clouds in the Milky Way and nearby galaxies and implies cloud radii of R ∼ 10 ¹⁻² pc. The absorbing clouds are found in a region of high obscuration inside a 30 kpc wide stellar nebula, as revealed by rest-frame near-ultraviolet imaging performed with the Hubble Space Telescope. The fact that we spectrally resolve molecular clouds at the onset of Cosmic Noon opens prospects for studying cloud chemistry and physics that drive the formation of stars in the early Universe.

We present MeerKAT observations searching for H I absorption in a sample of 17 powerful ( L _1.4 GHz > 10 ²⁷ W Hz ⁻¹ ) radio sources at intermediate redshifts (0.25 < z < 0.7). The sample is well characterised at radio and optical wavelengths, allowing us to connect the presence (or absence) of H I to the properties of the active galactic nucleus (AGN) and its host galaxy. The sample consists mostly of core-dominated sources and quasars. Half of the targets have a UV luminosity below the limit of L _UV = 10 ²³ W Hz ⁻¹ , whereby at values above this limit, the gas would be expected to be ionised by this radiation. We obtained 15 spectra free (or almost free) of radio frequency interference, reaching extremely low optical depths ( τ _peak < 0.005) resulting in three new H I absorption detections. Two are associated H I absorptions, giving a detection rate of such systems of 13%±7%. Both are found in a young radio source (PKS 1151–34 and PKS 1306–09), confirming the trend that this type of sources are more often detected in H I compared to more evolved ones. The UV luminosity of both these sources is below 10 ²³ W Hz ⁻¹ . Surprisingly, one of the detections (PKS 1151–34) is hosted by a quasar, suggesting that the radio lobes of this source are still embedded in the circumnuclear disc. In the second source (PKS 1306–09), the H I is highly blueshifted and likely part of the jet-driven outflow earlier observed in the warm ionised gas. This represents a new addition to the group of young radio AGNs, where multi-phased outflows have been observed as predicted by numerical simulations. A third detection is a ‘local intervening’ system, caused by a galaxy in the local environment of PKS 0405–12 and located in front of the southern radio lobe of this source, about 100 kpc in projection from this quasar. More such cases are expected to show up in large, blind surveys and our results show the need for high spatial resolution and good ancillary data to separate associated from intervening absorption. Overall, the results indicate a variety of plausible situations, which resemble what is seen at low redshifts. For the associated absorption, a combination of evolutionary status of the radio sources, physical conditions, and geometry of the gas structure determine the detection rate of H I absorption. The data also show the excellent capabilities of MeerKAT for obtaining very low optical depth detections, revealing the presence of an otherwise missed group of absorptions.

We present the third data release of the LOFAR Two-metre Sky Survey (LoTSS-DR3). The survey images cover 88% of the northern sky and were created from 12 950 h of data (18.6 PB) accumulated over 10.5 years. Producing the images took 20 million core hours of processing through direction-independent and direction-dependent calibration pipelines that correct for instrumental effects as well as spatially and temporally varying ionospheric distortions. In our 120–168 MHz continuum mosaic images with an angular resolution of 6″ (9″ below declination 10°) we catalogue 13 667 877 sources, formed from 16 943 656 Gaussian components. The scatter in the astrometric precision approximately follows the expected noise-like behaviour but with an additional systematic component of at least 0.24″ that is likely due to calibration imperfections. The random flux density scale error is 6%, while the systematic offset was previously shown to be within 2%. The median sensitivity of our mosaics is 92 μJy beam ⁻¹ , improving to 68 μJy beam ⁻¹ at high observing elevations, but degrading to 183 μJy beam ⁻¹ at the celestial equator due to station area projection effects. Completeness simulations, accounting for realistic source models, time- and bandwidth-smearing effects, and astrometric errors, indicate that we detect more than 95% of compact sources with integrated flux densities exceeding 9 times the local root mean square (RMS) noise. However, the recovered source counts in a particular integrated flux density bin do not match the injected counts until flux densities exceed 45 times the local RMS noise. The Euclidean-normalised differential source counts derived from the survey constrain the radio source population over five orders of magnitude and are in good agreement with previous deep and wide-area surveys. All data products are publicly available, including catalogues, individual-field Stokes I , Q , U , and V images, mosaicked Stokes I images, and uv data with associated direction-dependent calibration solutions.