POSSIBLE EVOLUTIONARY CONNECTION AMONGST THE DIFFERENT TYPES OF SEYFERT GALAXIES

A very large sample of Seyfert galaxies (217,272 galaxies) obtained from SDSS DR10 (Sloan Digital Sky Survey Data Release 10) were used for this study. The accretion rate (ṁ) was calculated from the bolometric luminosity (Lbol) and velocity dispersion (σ) using this relation: log ṁ = -36.977 + log Lbol – 4.02 log σ and using the M–sigma (M–σ) relation, the mass of the supermassive black hole was estimated as; MBH = 108 Mʘ × 3.1(σ/200kms-1)4. These calculated parameters enabled in ascertaining the nature of the different classes of Seyfert galaxies. The results obtained show that, as the black hole mass of an AGN (Seyfert galaxy) increases, there is a decrease in its accretion rate and the region of broad line emission progressively declines from its high intensity in Seyfert 1s to the point of disappearance. Galaxies at their early stage in life are very luminous and accretes matter at a very high rate, but as they get older their luminosities and accretion rate reduce with an associated increment in their black hole masses. And since this can only be achieved with time, I infer that there is a possible evolutionary sequence amongst the Seyfert galaxies in which Seyfert 1 galaxies evolve to Seyfert 2 galaxies.