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arXiv · 1706.00797

Properties of Narrow line Seyfert 1 galaxies

Suvendu Rakshit·C. S. Stalin·Hum Chand·Xue-Guang Zhang
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Abstract

Narrow line Seyfert 1 (NLSy1) galaxies constitute a class of active galactic nuclei characterized by the full width at half maximum (FWHM) of the H$β$ broad emission line < 2000 km/s and the flux ratio of [O III] to H$β$ < 3. Their properties are not well understood since only a few NLSy1 galaxies were known earlier. We have studied various properties of NLSy1 galaxies using an enlarged sample and compared them with the conventional broad-line Seyfert 1 (BLSy1) galaxies. Both the sample of sources have z $\le$ 0.8 and their optical spectra from SDSS-DR12 that are used to derive various physical parameters have a median signal to noise (S/N) ratio >10 per pixel. Strong correlations between the H$β$ and H$α$ emission lines are found both in the FWHM and flux. The nuclear continuum luminosity is found to be strongly correlated with the luminosity of H$β$, H$α$ and [O III] emission lines. The black hole mass in NLSy1 galaxies is lower compared to their broad line counterparts. Compared to BLSy1 galaxies, NLSy1 galaxies have a stronger FeII emission and a higher Eddington ratio that place them in the extreme upper right corner of the $R_{4570}$ - $ξ_{Edd}$ diagram. The distribution of the radio-loudness parameter (R) in NLSy1 galaxies drops rapidly at R > 10 compared to the BLSy1 galaxies that have powerful radio jets. The soft X-ray photon index in NLSy1 galaxies is on average higher (2.9 $\pm$ 0.9) than BLSy1 galaxies (2.4 $\pm$ 0.8). It is anti-correlated with the H$β$ width but correlated with the Fe II strength. NLSy1 galaxies on average have a lower amplitude of optical variability compared to their broad lines counterparts. These results suggest Eddington ratio as the main parameter that drives optical variability in these sources.

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Suvendu Rakshit, C. S. Stalin, Hum Chand, Xue-Guang Zhang. 2017-06-02. Properties of Narrow line Seyfert 1 galaxies. https://arxiv.org/abs/1706.00797

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