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Suvendu Rakshit, Chelliah Subramonian Stalin, Hum Chand & Xue-Guang Zhang

Properties of Narrow line Seyfert 1 galaxies

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Mots-clés : AGN, astronomie, astrophysique, extragalactique, variabilité


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 broad emission line <2000 km s-1 and the flux ratio of [O III] to H <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 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 pixel-1. A strong correlation between the H and Hα emission lines is found both in the FWHM and flux. The nuclear continuum luminosity is found to be strongly correlated with the luminosity of H, Hα 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 R4570 - λEdd 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 ± 0.9) than BLSy1 galaxies (2.4 ± 0.8). It is anti-correlated with the H width but correlated with the FeII 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.

Keywords : AGN, astronomy, astrophysics, extragalactic, variability

To cite this article

Suvendu Rakshit, Chelliah Subramonian Stalin, Hum Chand & Xue-Guang Zhang, «Properties of Narrow line Seyfert 1 galaxies», Bulletin de la Société Royale des Sciences de Liège [En ligne], Volume 87 - Année 2018, Actes de colloques, First Belgo-Indian Network for Astronomy & Astrophysics (BINA) workshop - November 2016 - Nainital, India, 379 - 386 URL :

About: Suvendu Rakshit

Indian Institute of Astrophysics, Block II, Koramangala, Bangalore-560034, India,

About: Chelliah Subramonian Stalin

Indian Institute of Astrophysics, Block II, Koramangala, Bangalore-560034, India

About: Hum Chand

Aryabhatta Research Institute of Observational Sciences (ARIES), 263002, Nainital, India

About: Xue-Guang Zhang

Institute of Astronomy and Space Science, Sun Yat-Sen University, No. 135, Xingang Xi Road, Guangzhou, 510275, P. R. China