Abstract
We present statistical results from a very large sample of Seyfert galaxies (217,272 galaxies) obtained from SDSS DR10 (Sloan Digital Sky Survey Data Release 10). From their observed parameters which includes; flux of hydrogen alpha (Hα), luminosity distance and velocity dispersion, we computed other relevant parameters such as; bolometric luminosity, black hole mass and mass accretion rate, which enabled us classify these Seyfert galaxies into Seyfert 1s (188,486 galaxies) and Seyfert 2s (28,786 galaxies). Analyses on these computed parameters revealed that Seyfert 2 galaxies were less luminous, more massive and accrete less matter than the Seyfert 1 galaxies. Further analysis on Seyfert 2s based on their mass accretion rate led to their classification into hidden broad line region (HBLR) Seyfert 2s (12,988 galaxies) and non-hidden broad line region (non-HBLR) Seyfert 2s (15,798 galaxies) which shows that, the HBLR S2s accrete more matter than the non-HBLR S2s. All the results obtained suggest that the bolometric luminosity alone is not sufficient in determining the extent of the existence of the BLR in Seyfert 2 galaxies rather the mass accretion rate should be taking into consideration in determining the appearance and disappearance of the BLR.
Highlights
Seyfert galaxies are a subclass of active galactic nuclei (AGN) and are categorized as low luminosity, radio-quiet AGN, hosted in spiral or lenticular galaxies [1]
The Seyfert 2 galaxies were further classified into hidden broad line region (HBLR) and non-hidden broad line region Seyfert 2 galaxies based on their accretion rate (ṁ); ṁ > ṁmin= HBLR, while ṁ ≤ ṁmin = nonHBLR
As the black hole mass of an AGN (Seyfert galaxy) increases, there is a decrease in its bolometric luminosity and accretion rate and the region of broad line emission progressively declines from its high intensity in Seyfert 1s to the point of disappearance at sufficiently low bolometric luminosity (Seyfert 2s)
Summary
Seyfert galaxies are a subclass of active galactic nuclei (AGN) and are categorized as low luminosity, radio-quiet AGN, hosted in spiral or lenticular galaxies [1]. Seyfert galaxies are one of the largest groups of active galaxies, along with quasars They have similar nucleus like quasars (very luminous, distant and bright sources of electromagnetic radiation) with very high surface brightness whose spectra reveal strong, high-ionization emission lines [3], but unlike quasars, their host galaxies are clearly detectable [4, 5]. They have super massive black hole (SMBH) at their centers which are surrounded by accretion discs of in-falling materials. Each part of the accretion disc has a different velocity relative to our line of sight, and the faster the gas is rotating around the black hole, the broader the emission line will be [8]
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