ALBERT

Description: The azimuthal variation of the H II region oxygen abundance in spiral galaxies is a key observable for understanding how quickly oxygen produced by massive stars can be dispersed within the surrounding interstellar medium. Observational constraints on the prevalence and magnitude of such azimuthal variations remain rare in the literature. Here, we report the discovery of pronounced azimuthal variations of H II region oxygen abundance in NGC 2997, a spiral galaxy at approximately 11.3 Mpc. Using 3D spectroscopic data from the TYPHOON Program, we have studied the H II region oxygen abundance at a physical resolution of 125 pc. Individual H II regions or complexes are identified in the 3D optical data and their strong emission line fluxes measured to constrain their oxygen abundances. We find 0.06 dex azimuthal variations in the oxygen abundance on top of a radial abundance gradient that is comparable to those seen in other star-forming disks. At a given radial distance, the oxygen abundances are highest in the spiral arms and lower in the inter-arm regions, similar to what has been reported in NGC 1365 using similar observations. We discuss whether the azimuthal variations could be recovered when the galaxy is observed at worse physical resolutions and lower signal-to-noise ratios.

Description: Context. Although studying outflows in the host galaxies of active galactic nuclei (AGNs) have moved to the forefront of extragalactic astronomy in recent years, estimating the energy associated with these outflows has been a major challenge. Determining the energy associated with an outflow often involves an assumption of uniform density in the narrow line region (NLR), which spans a wide range in the literature, leading to large systematic uncertainties in energy estimation. Aims. In this paper we present electron density maps for a sample of outflowing and non-outflowing Seyfert galaxies at z 〈 0.02 drawn from the Siding Spring Southern Seyfert Spectroscopic Snapshot Survey (S7) and try to understand the origin and values of the observed density structures to reduce the systematic uncertainties in outflow energy estimation. Methods. We use the ratio of the [S II]λ6716,6731 emission lines to derive spatially resolved electron densities (≲50–2000 cm−3). Using optical Integral Field Unit observations from the Wide Field Spectrograph (WiFeS), we are able to measure densities across the central 2–5 kpc of the selected AGN host galaxies. We compare the density maps with the positions of the H II regions derived from the narrow Hα component, ionization maps from [O III] and spatially resolved BPT diagrams to infer the origin of the observed density structures. We also use the electron density maps to construct density profiles as a function of distance from the central AGN. Results. We find a spatial correlation between the sites of high star formation and high electron density for targets without an active ionized outflow. The non-outflowing targets also show an exponential drop in the electron density as a function of distance from the centre, with a mean exponential index of ∼0.15. The correlation between the star forming sites and electron density ceases for targets with an outflow. The density within the outflowing medium is not uniform and shows both low- and high-density sites, most likely due to the presence of shocks and highly turbulent medium. We compare these results in the context of previous results obtained from fibre and slit spectra.