Prof. Dimitra Rigopoulou

Abstract:

We present a far-ultraviolet (FUV) analysis of the star-forming complexes (SFCs) in the nearby spiral galaxy NGC 2090 based on observations from the Ultraviolet Imaging Telescope, and compare the FUV emission with that from the optical and infrared bands. NGC 2090 exhibits prominent star formation in its extended outer disk, with FUV emission traced out to ∼30 kpc, far beyond the truncation of the old stellar disk at ∼5 kpc. It is classified as an extended UV (XUV) disk galaxy. We identified and characterized the SFCs both within and beyond the optical radius (R 25 ), estimating their physical sizes and star formation rates (SFRs). The outer-disk SFCs are generally smaller in area and show a narrower distribution of SFR surface density (Σ SFR ) compared to the inner-disk SFCs. We investigated the properties of the inner disk using mid-infrared data from the James Webb Space Telescope and find that the polycyclic aromatic hydrocarbon emission is strongly correlated with regions of active star formation. The specific SFR increases with radius, consistent with a scenario of inside-out disk growth. The observed number of SFCs and their H α -to-FUV flux ratios in the outer disk of NGC 2090 indicate ongoing massive star formation and are consistent with a top-heavy initial mass function (IMF), implying that the upper end of the IMF is not truncated in the low-density, metal-poor outskirts. These results suggest that XUV disks can host significant massive star formation despite their low stellar densities and metallicities.

Abstract:

We present a detailed study of the inner regions of NGC 7582, a nearby Seyfert 2 galaxy, from the Galaxy Activity, Torus, and Outflow Survey (GATOS). The galaxy hosts a circumnuclear star-forming disc and an active galactic nucleus (AGN)-driven biconical ionized outflow. Using James Webb Space Telescope Near-Infrared Spectrograph (NIRSpec) and Mid-Infrared Instrument/Medium-Resolution Spectrometer (MIRI/MRS) integral-field spectroscopy, we analyse ionic emission lines spanning a wide range of ionization potentials (IPs, –126 eV). Gaussian line-profile fitting reveals kinematic stratification: low-IP species ( eV; e.g. [Fe ii], [Ar ii], and [Ne ii]) trace ordered disc rotation with PA , while high-IP species ( eV; e.g. [O iv], [Mg iv], and [Ne v]) follow the outflow with PA . Outflowing gas exhibits systematically higher velocity dispersions ( km s−1) than the disc ( km s−1), consistent with turbulent or bulk motions. Intermediate-IP lines, [S iii], [Ar iii], and [Ne iii], show contributions from both components, with the outflow characterized by higher dispersion, lower amplitude, and higher velocities in double-Gaussian fits. For these lines, a thin inclined disc plus 1D outflow model enables robust separation and quantification of the disc and outflow velocity fields. The outflow is consistent with a hollow bicone capable of accelerating gas beyond the local escape velocity, implying most material is unlikely to be re-accreted. The ionization cone opening angle shows no dependence on IP, indicating the AGN torus polar regions are largely unobscured. Our study provides new insights into AGN-driven outflows and circumnuclear disc dynamics, offering a framework to disentangle overlapping interstellar medium kinematics in nearby active galaxies.

Abstract:

We utilize James Webb Space Telescope/Mid Infrared Instrument (JWST/MIRI) Integral Field Unit observations from the Galaxy Activity, Torus and Outflow Survey to investigate the diverse range of ionized outflow rates of obscured active galactic nuclei (AGN) with similar bolometric luminosity and explore potential associations with AGN feedback. We explore spatial correlations between ionized emission potentially associated with fast shocks ([Fe II]5.34μm) and the excitation of H2. We further constrain our investigation to the inner 400 pc (the nuclear and circumnuclear regions r < 200 pc), and estimate the excitation temperature and column density of H2 assuming local thermodynamic equilibrium and using the S(1)–S(8) rotational H2 emission lines visible to JWST/MIRI spectroscopy. We report the molecular gas temperature of the deprojected 400 pc nuclear region to correlate with the ionized mass outflow rate. We also observe a stronger degree of spatial correlation between [Fe II]5.34μm emission and H2 gas temperature. We observe regions of enhanced [Fe II]5.34μm/[Ar II]6.99μm spatially coincident with the ionization cones of objects with higher ionized outflow rates and [Fe II]5.34μm/[Ar II]6.99μm in the deprojected 400 pc nuclear region to scale positively with both the ionized outflow rate and the estimated molecular gas temperature. We do not observe the estimated jet cavity power within the central 400 pc as strongly correlated with the ionized mass outflow rate or molecular gas temperature of the nuclear region. We take the preceding observations to suggest a higher degree of interaction between AGN outflows and the circumnuclear disk.