arXiv subjects

L. Evangelista

Publications and source records attributed to L. Evangelista.

4 recordsLinked to original sources

arXiv2026

MICONIC: The spatial relationship between star formation and the AGN in Centaurus A revealed by JWST/MIRI

Centaurus A (Cen A), the nearest active radio galaxy, hosts a warped dust disc formed in a gas-rich merger. We present JWST/MIRI imaging in three filters, F560W, F770W, and F1130W, of this central disc over a ~4 x 2 kpc region to characterise its resolved mid-infrared stellar populations. The images reveal a system of extended dusty structures, previously identified with Spitzer as an "oval dusty shell", now resolved into multiple loop-like features that are brightest in F1130W and closely associated with the warped disc. Colour-magnitude and colour-colour diagnostics reveal a distinct population of 928 red point sources with strong infrared excess, accounting for ~36 per cent of sources with high-quality photometry in all three bands, spatially confined to the disc. These sources exhibit rising mid-infrared spectral slopes indicative of emission from warm dust. Their colours and spatial distribution are consistent with a population dominated by embedded young stellar objects, tracing recent (~10^5-10^6 yr) star formation within the disc. The strong geometric alignment of these sources with the disc, together with the lack of correlation with the radio jet, suggests that star formation in the central regions of Cen A is primarily regulated by merger-accreted gas, with no strong evidence for AGN jet-ISM interactions.

astro-ph.GA↗

arXiv2026

MICONIC: The multiphase circumnuclear region of Centaurus A as seen with JWST/MIRI MRS observations. I. Spectral inventory and properties of the warm molecular disk

Supermassive black holes power Active Galactic Nuclei (AGN), injecting energy that regulates accretion and shapes host galaxies. We investigate the morphology, excitation, and kinematics of molecular hydrogen (H2) in the inner circumnuclear disk of Centaurus A, the nearest radio galaxy. We present JWST/MIRI MRS integral-field spectroscopy of the central 170x100 pc2 at 0.3"-0.7" (5-12 pc) resolution, focusing on pure rotational H2 lines. The spectra show strong nuclear continuum and bright H2 emission from S(1) to S(8), including the first S(8) detection in Centaurus A. Optically thin nuclear lines enable maps of temperature, column density, and ortho-to-para ratio from spaxel-level excitation-diagram fitting. Warm H2 shows a complex morphology, dominating the central region where CO emission is weak or undetected. Low-excitation H2 lines trace an inhomogeneous ring with a 20-pc-radius cavity aligned with the jet's near side, suggesting that the jet affects the morphology of the molecular disk. Higher-excitation lines form filamentary structures around the AGN. Kinematics are rotational with an S-shaped distortion, indicating non-circular motions or a warped disk. A coherent, low-dispersion (70 km/s) streamer spirals inward. A power-law temperature distribution yields a warm (100-2000 K) H2 mass of (5.6+/-1.4)e5 Msun and a dynamical mass of 5e8 Msun within 100 pc. Shock excitation is supported by enhanced H2/continuum and H2/PAH ratios, elevated [Ne III]/[Ne II], and sub-equilibrium ortho-to-para ratios (1.6-2.4). Turbulent dissipation can balance H2 cooling and likely dominates heating beyond 30 pc. In the inner 100 pc of Centaurus A, AGN feeding and feedback are linked: shocks excite H2, regulate the gas temperature, and prevent cooling below 100 K, explaining the weak CO emission and lack of a massive outflow. These shocks may drive angular momentum loss and help fuel the nucleus.

astro-ph.GA↗

arXiv2026

MICONIC: JWST/MIRI-MRS reveals heavily reprocessed PAH emission in the circum-nuclear disc of Centaurus A

Polycyclic aromatic hydrocarbons (PAHs) are key dust components in galaxies and play a fundamental role in the physics of the interstellar medium (ISM), yet their response to AGN feedback remains debated. We present a spatially resolved analysis of PAHs in the central $7^{\prime\prime}\times12^{\prime\prime}$ ($\sim100\times200$ pc$^2$) of Centaurus A. We use JWST/MIRI-MRS observations at 5-28 $μ$m from the MIRI European consortium GTO program MICONIC, with angular resolution of $0.35^{\prime\prime}-1^{\prime\prime}$ (about 6-17 pc). We derive PAH moment-0 maps via local continuum subtraction and extract one-dimensional spectra from five regions of interest, including the nucleus, the circumnuclear disc, and a PAH-deficient region. The spectra are decomposed into continuum, emission lines, and PAHs to measure feature intensities and equivalent widths (EWs). PAH emission is primarily distributed in a ring-like structure with localized enhancements at $\sim40$ pc from the nucleus. A distinct PAH-deficient region is observed to the north-west, roughly perpendicular to the jet axis, and coincident with enhanced ionized-gas velocity dispersion and inflowing molecular streamers. The 11.3/7.7 $μ$m and 6.2/7.7 $μ$m ratios exceed model predictions for pericondensed PAHs, indicating processed populations with more open structures. The 11.3/12.7 $μ$m ratio suggests a dominance of solo hydrogen sites and partial dehydrogenation, particularly in the PAH-deficient region, where shocks likely drive erosion. The largest EWs are found in the ring, while reduced values in the deficient region point to partial destruction; in the nucleus, low EWs are mainly due to continuum dilution.

astro-ph.GA↗

arXiv2025

MICONIC: JWST/MIRI MRS reveals a fast ionized gas outflow in the central region of Centaurus A

We present a kinematical study of the ionized and molecular gas in the central region (~7-14"~100-200pc) of the nearby radio galaxy Cen A. We used JWST/MIRI MRS 5-28$μ$m observations taken as part of the MIR Characterization of Nearby Iconic galaxy Centers (MICONIC) of the MIRI EC. The two gas phases present contrasting morphologies and kinematics. The brightest emission from the ionized gas, traced with a range of IP lines ([Fe II] to [Ne VI]), is extended along the direction of the radio jet. We also detected emission from low IP emission lines and H$_2$ transitions in the galaxy disk. Both gas phases present rotational motions but also complex kinematics. The observations reveal several ionized gas kinematical features that are consistent with simulation predictions of a jet-driven bubble and outflow interacting with the galaxy ISM. These include broad components in the nuclear line profiles ($σ$~600km/s), high velocities (~ +1000, -1400km/s) confined within the nuclear region, velocities of hundreds of km/s in several directions in the central 2", and enhanced velocity dispersions perpendicular to the radio jet. Moreover, we find evidence of shock excitation in the nuclear region based on MIR line ratios. We compared the ionized gas mass outflow rate with Cen A's AGN luminosity and radio jet power and demonstrate that both mechanisms provide sufficient energy to launch the outflow. The noncircular motions observed in the H$_2$ lines can be reproduced with either a warped rotating disk model or a radial component. The latter might be to related to gas streamers detected in cold molecular gas. There is no clear indication of a fast nuclear H$_2$ outflow, only a weak blueshifted component. This could be due to a relatively low nuclear warm H$_2$ column density and/or the limited geometrical coupling of Cen A's inner radio jet with the circumnuclear disk of the galaxy. (Abridged)

astro-ph.GA↗