IFU spectroscopy of 10 early type galactic nuclei: II - Nuclear emission line properties

Abstract

Although it is well known that massive galaxies have central black holes, most of them accreting at low Eddington ratios, many important questions still remain open. Among them, are the nature of the ionizing source, the characteristics and frequencies of the broad line region and of the dusty torus. We report observations of 10 early-type galactic nuclei, observed with the IFU/GMOS spectrograph on the Gemini South telescope, analysed with standard techniques for spectral treatment and compared with results obtained with principal component analysis Tomography (Paper I). We performed spectral synthesis of each spaxel of the data cubes and subtracted the stellar component from the original cube, leaving a data cube with emission lines only. The emission lines were decomposed in multi-Gaussian components. We show here that, for eight galaxies previously known to have emission lines, the narrow line region can be decomposed in two components with distinct line widths. In addition to this, broad H$\alpha$ emission was detected in six galaxies. The two galaxies not previously known to have emission lines show weak H$\alpha$+[N II] lines. All 10 galaxies may be classified as low-ionization nuclear emission regions in diagnostic diagrams and seven of them have bona fide active galactic nuclei with luminosities between 10${}^{40}$ and 10${}^{43}$ erg s${}^{-1}$. Eddington ratios are always < 10${}^{-3}$.

16 pages, 9 figures, accepted for publication in MNRAS

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• The DIVING${}^{3D}$ Survey - Deep IFS View of Nuclei of Galaxies - III. Analysis of the nuclear region of the early-type galaxies of the sample
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• IFU observations of the inner 200 pc of NGC 4546: gas rotation, non-circular motions and ionised outflows
• Digging deeper into NGC\,6868 I: stellar population
• Measuring the mass of the supermassive black hole of the lenticular galaxy NGC 4546
• Digging deeper into NGC 6868 II: ionized gas and excitation mechanism