Evidences of merging in the Seyfert galaxy NGC 3393 revealed by modelling the spectra

Abstract

The discovery of two active black holes in the Seyfert galaxy NGC 3393, separated by about 490 light years, revealed a merging event. This led us to look for other evidences of galaxy collision and merging through the analysis of the observed spectra in different frequency ranges. We found preshock densities higher by a factor of about 10 in the NGC 3393 NLR than in other AGN and patches of ionized matter beyond the observed NLR bulk. They can be explained by compression and heating of the gas downstream of shock waves created by collision. Metallicity in terms of the O/H relative abundance, is about 0.78 solar. Mg/H depletion by a factor of about 3 compared with solar cannot be explained by Mg trapping into dust grains, due to rather high shock velocities. The low O/H and Mg/H abundances indicate mixing with external matter during collision. Twice solar N/H is predicted by modelling the spectra of high shock velocity clouds reached by a Ts =8.6 10^4 K black-body flux. This suggests that Wolf-Rayet stars could be created by galaxy collision in the central region.

11 pages, 3 figures, 3 tables, accepted for publication in MNRAS

References in corpus (7)

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• On the central abundances of Active Galactic Nuclei and Star-forming Galaxies
• New quantitative nitrogen abundance estimations in a sample of Seyfert 2 Active Galactic Nuclei
• New metallicity calibration for Seyfert 2 galaxies based on the N2O2 index
• CHEERS Results from NGC 3393, II: Investigating the Extended Narrow Line Region using Deep Chandra Observations and Hubble Narrow Line Imaging
• Chemical abundances of Seyfert 2 AGNs IV. Composite models calculated by photoionization + shocks
• The merger Seyfert galaxy Arp 220. Line and continuum absorption and emission
• Distribution of the heavy elements throughout the extended narrow line region of the Seyfert galaxy NGC 7212