Are Narrow-line Seyfert 1 Galaxies Powered by Low-mass Black Holes?

Abstract

Narrow line Seyfert 1 galaxies (NLS1s) are believed to be powered by accretion of matter onto low mass black holes (BHs) in spiral host galaxies with BH masses M BH ∼ 10 6 -10 8 M . However, the broad band spectral energy distribution of the γ-ray emitting NLS1s are found to be similar to flat spectrum radio quasars. This challenges our current notion of NLS1s having low M BH . To resolve this tension of low M BH values in NLS1s, we fitted the observed optical spectrum of a sample of radio-loud NLS1s (RL-NLS1s), radio-quiet NLS1s (RQ-NLS1s) and radio-quiet broad line Seyfert 1 galaxies (RQ-BLS1s) of ∼500 each with the standard Shakura-Sunyaev accretion disk (AD) model. For RL-NLS1s we found a mean log(M AD BH /M ) of 7.98±0.54. For RQ-NLS1s and RQ-BLS1s we found mean log(M AD BH /M ) of 8.00±0.43 and 7.90±0.57, respectively. While the derived M AD BH values of RQ-BLS1s are similar to their virial masses, for NLS1s the derived M AD BH values are about an order of magnitude larger than their virial estimates. Our analysis thus indicates that NLS1s have M BH similar to RQ-BLS1s and their available virial M BH values are underestimated influenced by their observed relatively small emission line widths. Considering Eddington ratio as an estimation of the accretion rate and using M AD BH , we found the mean accretion rate of our RQ-NLS1s, RL-NLS1s and RQ-BLS1s as 0.06 +0.16 −0.05 , 0.05 +0.18 −0.04 and 0.05 +0.15 −0.04 , respectively. Our results therefore suggest that NLS1s have BH masses and accretion rates similar to BLS1s.

Jet Properties of Compact Steep-Spectrum Sources and an Eddington-Ratio-Driven Unification Scheme of Jet Radiation in Active Galactic Nuclei

“…In order to further investigate the properties of γ-ray emitting CSSs, we collect the large sample data of CSSs and RL-NLS1s 5 together with a RG sample from the literature (Liao & Gu et al 2020;Viswanath et al 2019;Berton et al 2016). We plot R Edd against M BH for these sources together with the γ-ray emitting AGNs in Figure 11.…”

“…It was suggested that M BH of NLS1s derived from the emission line may be underestimated(Collin et al 2006;Zhu et al 2009;Calderone et al 2013;Viswanath et al 2019), hence the M BH values of RL-NLS1s in this paper are estimated by fitting the big blue bump spectrum with the standard accretion disk model(Calderone et al 2013;Viswanath et al 2019). …”

Relativistic Jets in Gamma-Ray-Emitting Narrow-Line Seyfert 1 Galaxies

“…It appears that the BH masses estimated with the virial method in γ-ray-emitting NLSy1 are systematically and significantly smaller that those derived from other techniques. It is worth mentioning that fitting the optical-UV spectrum of a sample of both radio-quiet and radio-loud NLSy1 (including 4 of the 9 γ-ray-emitting NLSy1) with the standard Shakura & Sunyaev accretion disc, [24] has obtained BH masses that are about an order of magnitude larger than their virial estimates. A higher BH mass estimation may solve the problem of the minimum BH mass required for the formation of relativistic jets, but it leaves open the host galaxy issue.…”

Intra-night optical variability study of a non-jetted narrow-line Seyfert 1 galaxy: SDSS J163401.94+480940.1

“…Observational evidence suggests that the average estimated black hole mass of NLSy1s based upon various methods such as reverberation mapping, luminosity-radius relationship, and single-epoch virial method, has been found to be relatively lower ∼ 10 6 − 10 7 M (Grupe & Mathur, 2004;Deo et al, 2006;Zhou et al, 2006;Peterson, 2011;Wang et al, 2014;Rakshit et al, 2017), and they accrete with a high fraction of the Eddington rate, in contrast to quasars (Boroson & Green, 1992;Peterson et al, 2000). However, a systematic underestimation of their black hole masses is suggested (Decarli et al, 2008;Marconi et al, 2008;Calderone et al, 2013;Viswanath et al, 2019;Ojha et al, 2020a). NLSy1s are mainly hosted by spiral/disc galaxies (Deo et al, 2006;Ohta et al, 2007;Olguín-Iglesias et al, 2020).…”