Communications of BAO, Vol. 67, Issue 2, 2020, pp. 219-226 Properties of Broad and Narrow Line Seyfert galaxies selected from SDSS Vivek Kumar Jha *1 , Hum Chand 2 , and Vineet Ojha 1 1 Aryabhatta research institute of observational sciences (ARIES), Nainital, Uttarakhand, India 2 Central University of Himachal Pradesh (CUHP), Dharamshala, Himachal Pradesh, India Abstract A comparative study of a representative sample of Broad and Narrow line Seyfert galaxies is presented. These galaxies have been selected from the 16 th data release of the Sloan Digital Sky Survey (SDSS-DR16). Some of the properties derived from single epoch spectrum vary significantly between the two populations. We find that the emission regions of Narrow line Seyfert galaxies are rich in iron content and the accretion rate is higher compared to the Broad line Seyfert galaxies. In our analysis, the Hβ emission line is found to be asymmetric in few of the galaxies with more number of Narrow-line Seyfert 1 (NlSy1) galaxies showing blue asymmetries i.e. traces of outflowing gas as compared to the Broad-line Seyfert 1 (BlSy1) galaxies. This behaviour may be explained by the higher iron content present in the emission line regions of NlSy1 galaxies. Keywords: galaxies: active – galaxies: nuclei – galaxies: Seyfert 1. Introduction Seyfert galaxies are characterized by a lower luminous active nucleus as compared to the general quasar population. Among the Seyfert galaxies, Type-1 galaxies show both narrow and broad emission lines (see Netzer, 2015, for a review). These lower luminous Type-1 galaxies are subdivided into narrow and broad line Seyfert classes based on the Full Width at Half Maximum (FWHM) of the Hβ emission line. NlSy1 galaxies are understood to be a subclass of active galactic nuclei (AGN) which have narrower broad Balmer line widths with FWHM of broad Hβ emission line ≤ 2000 km/sec -1 ,a small intensity ratio of the [O III] λ5007 to Hβ line ( [OIII ]/Hβ ≤ 3), stronger optical Fe II emissions (see Rakshit et al., 2017, and references therein), and usually steeper soft X-ray spectra and more rapid X-ray and sometimes optical flux variability (see Ojha et al., 2020a) . It is assumed that these properties are due to the central black hole being less massive, but accreting at a very high rate. Low optical variability has also been reported in NlSy1 galaxies by Rakshit & Stalin (2017). It has been proposed by Mathur (2000) that the NlSy1 galaxies are a subcategory of BlSy1 galaxies only and can be assumed to be in evolutionary stages, while in Gaskell (2000) unusually high Fe-II strength, R fe in NlSy1 galaxies is attributed to weak Balmer lines originating from a dense environment. The NlSy1 galaxies have been proposed as younger versions of the general broad line active galaxies. The region responsible for the generation of broad emission lines is known as the Broad line Region (BLR). About 120 AGN been studied using the reverberation mapping technique (see Bahcall et al., 1972, Blandford & McKee, 1982), which is a powerful time domain method to probe the inner regions of type 1 galaxies. However, with the known number of AGN extending into hundreds of thousands, thanks to the all sky surveys such as the Sloan Digital Sky Survey (SDSS) (York et al., 2000) but precise knowledge of the structure and kinematics of BLR through reverberation mapping available for only a handful of AGN (see Bentz & Katz, 2015, for a comprehensive database of reverberation mapped AGN), studies have relied on statistical analysis on a selected sample of AGN constrained by * vivek@aries.res.in, Corresponding author Vivek Kumar Jha et al. 219 DOI: 10.52526/25792776-2020.67.2-219