Upholding the Unified Model for Active Galactic Nuclei: VLT/FORS2 Spectropolarimetry of Seyfert 2 galaxies
| Autor: | Almeida, Cristina Ramos, Gonzalez, M. J. Martínez, Ramos, A. Asensio, Acosta-Pulido, J. A., Hönig, S. F., Alonso-Herrero, A., Tadhunter, C. N., González-Martín, O. |
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| Rok vydání: | 2016 |
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| Druh dokumentu: | Working Paper |
| DOI: | 10.1093/mnras/stw1388 |
| Popis: | The origin of the unification model for Active Galactic Nuclei (AGN) was the detection of broad hydrogen recombination lines in the optical polarized spectrum of the Seyfert 2 galaxy (Sy2) NGC 1068. Since then, a search for the hidden broad-line region (HBLR) of nearby Sy2s started, but polarized broad lines have only been detected in 30-40% of the nearby Sy2s observed to date. Here we present new VLT/FORS2 optical spectropolarimetry of a sample of 15 Sy2s, including Compton-thin and Compton-thick sources. The sample includes six galaxies without previously published spectropolarimetry, some of them normally treated as non-hidden BLR (NHBLR) objects in the literature, four classified as NHBLR, and five as HBLR based on previous data. We report >=4{\sigma} detections of a HBLR in 11 of these galaxies (73% of the sample) and a tentative detection in NGC 5793, which is Compton-thick according to the analysis of X-ray data performed here. Our results confirm that at least some NHBLRs are misclassified, bringing previous publications reporting differences between HBLR and NHBLR objects into question. We detect broad H{\alpha} and H{\beta} components in polarized light for 10 targets, and just broad H{\alpha} for NGC 5793 and NGC 6300, with line widths ranging between 2100 and 9600 km/s. High bolometric luminosities and low column densities are associated with higher polarization degrees, but not necessarily with the detection of the scattered broad components. Comment: 18 pages, 19 figures (including appendices). Accepted in MNRAS |
| Databáze: | arXiv |
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