A comparative analysis of the active galactic nucleus and star formation characteristics of broad- and narrow-line Seyfert 1 galaxies

Abstract

We report here our comparative analysis of the active galactic nucleus (AGN) and star formation (SF) characteristics of a sample of narrow-line Seyfert 1 (NLS1) and broad-line Seyfert 1 (BLS1) galaxies. Our sample consisted of 373 BLS1 and 240 NLS1 galaxies and spanned the redshift 0.02 < z < 0.8. The broad-band spectral energy distribution, constructed using data from the ultra-violet to the far-infrared, was modelled using CIGALE to derive the basic properties of our sample. We searched for differences in stellar mass (M*), star formation rate (SFR), and AGN luminosity (LAGN) in the two populations. We also estimated new radiation-pressure-corrected black hole masses for our sample of BLS1 and NLS1 galaxies. While the virial black hole mass (MBH) of BLS1 galaxies is similar to their radiation-pressure-corrected MBH values, the virial MBH values of NLS1 galaxies are underestimated. We found that NLS1 galaxies have a lower MBH of log (MBH [M⊙]) = 7.45 ± 0.27 and a higher Eddington ratio of log (λEdd) = −0.72 ± 0.22 than BLS1 galaxies, which have log (MBH [M⊙]) and λEdd values of 8.04 ± 0.26 and −1.08 ± 0.24, respectively. The distributions of M*, SFR, and specific star formation (sSFR = SFR/M*) for the two populations are indistinguishable. This analysis is based on an independent approach and contradicts reports in the literature that NLS1 galaxies have a higher SF than BLS1 galaxies. While we found that LAGN increases with M*, LSF flattens at high M* for both BLS1 and NLS1 galaxies. The reason may be that SF is suppressed by AGN feedback at M* higher than ∼1011 M⊙ or that the AGN fuelling mechanism is decoupled from SF. Separating the sample into radio-detected and radio-undetected subsamples, we found no difference in their SF properties suggesting that the effect of AGN jets on SF is negligible.