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arXiv · 1008.5039

The study of Seyfert 2 galaxies with and without infrared broad lines

Hong-bing Cai·Xin-Wen Shu·Zhen-Ya Zheng·Jun-xian Wang
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Abstract

From the literature, we construct from literature a sample of 25 Seyfert 2 galaxies (S2s) with a broad line region detected in near infrared spectroscopy and 29 with NIR BLR which was detected. We find no significant difference between the nuclei luminosity (extinction-corrected [OIII]~5007) and infrared color $\rm{f_{60}/f_{25}}$ between the two populations, suggesting that the non-detections of NIR BLR could not be due to low AGN luminosity or contamination from the host galaxy. As expected, we find significantly lower X-ray obscurations in Seyfert 2s with NIR BLR detection, supporting the unification scheme. However, such a scheme was challenged by the detection of NIR BLR in heavily X-ray obscured sources, especially in six of them with Compton-thick X-ray obscuration. The discrepancy could be solved by the clumpy torus model and we propose a toy model demonstrating that IR-thin X-ray-thick S2s could be viewed at intermediate inclinations, and compared with those IR-thick X-ray-thick S2s. We note that two of the IR-thin X-ray-thick S2s (NGC 1386 and NGC 7674) experienced X-ray transitions, i.e. from Compton-thin to Compton-thick appearance or vice versa based on previous X-ray observations, suggesting that X-ray transitions could be common in this special class of objects.

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Hong-bing Cai, Xin-Wen Shu, Zhen-Ya Zheng, Jun-xian Wang. 2010-08-30. The study of Seyfert 2 galaxies with and without infrared broad lines. https://doi.org/10.1088/1674-4527%2F10%2F5%2F003

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