Narrow-line Seyfert 1s: what is wrong in a name?

Abstract

Narrow-line Seyfert 1s (NLSy1s) are an ill-defined class. Work done over the past 20 years as well as recent analyses show a continuity in properties (e.g., Balmer line profiles, blueshifts of high-ionization lines) between sources with FWHM above and below 2000 km s −1 , the defining boundary of NLSy1s. This finding alone suggests that comparisons between samples of NLSy1s and rest of broad-line AGNs are most likely biased. NLSy1s can be properly contextualized by their location on the quasar main sequence originally defined by Sulentic et al [1]. At one end, NLSy1s encompass sources with strong FeII emission and associated with high Eddington ratio that hold the promise of becoming useful distance indicators; at the other end, at least some of them are sources with broad profiles seen face-on. Any rigid FWHM limit gives rise to some physical ambiguity, as the FWHM of low-ionization lines depends in a complex way on mass, Eddington ratio, orientation, and luminosity. In addition, if the scaling derived from luminosity and virial dynamics applies to the broad line regions, NLSy1s at luminosity higher than 10 47 erg s −1 become physically impossible. Therefore, in a broader context, a proper subdivision of two distinct classes of AGNs and quasars may be achieved by the distinction between Pop. A and B with boundary at ≈ 4000 km s −1 in samples at z < 1, or on the basis of spectrophotometric properties which may ultimately be related to differences in accretion modes if high-luminosity quasars are considered.Revisiting narrow-line Seyfert 1 galaxies and their place in the Universe -NLS1 Padova

Past, Present, and Future of the Scaling Relations of Galaxies and Active Galactic Nuclei

“…A toy scheme can explain in a qualitative way the occupation of the MS plane under the assumptions that Eddington ratio, mass, and an aspect angle θ (i.e., the angle between the line-ofsight and the accretion disk axis) are the parameters setting the location of quasar along the MS (Marziani et al, 2001;Marziani et al, 2018). If the BLR radius follows a scaling power-law with luminosity (r ∝ L a , Kaspi et al (2000), Bentz et al (2013)), under the standard virial assumption, then…”

“…The two grids were computed for M BH 10 8 M 0 and 10 9 M 0 (gray), for several values of L/L Edd and for viewing angle θ between 0 and 40 °, following the toy model described in the text and in more detail in Ref. (Marziani et al, 2018). In the left panel, the labels identify the areas of Population A and B (respectively below and above the FWHM limit at 4,000 km s −1 ), and of extreme Population A (R FeII ≳ 1).…”

Properties of the continuum and broad line emission gas in active galactic nuclei with moderate to strong Feii emission

“…F 𝜆 is the flux at the wavelength 𝜆, C is a normalization constant, and 𝛼 is the power-law spectral index. (b) Hot dust heated by the AGN and likely associated with the dusty torus (Rodríguez-Ardila & Mazzalay 2006). This component shows up in the NIR and may dominate over the power-law if the dust is heated at temperatures close to the sublimation temperature of the dust grains T dust > 1500 K. That component is well described by a blackbody (BB) function, being the temperature T of the BB representative of T dust .…”

“…Another question still open is related to the excitation mechanisms leading to the formation of the Feii lines. In particular, the NIR lines at 𝜆9997, 𝜆10502, 𝜆10863, and 𝜆11127, collectively known as the Feii 1 μm lines (Rodríguez-Ardila et al 2002) can be formed either by Ly𝛼-fluorescence, collisional excitation, recombination, or a mix of these processes. The importance of this subject is because in the NIR the Feii lines are semi-blended or isolated, allowing for an accurate study of the line profiles and the physics of the region where that emission is formed.…”

Jet-Induced Feedback in the [O III] Lines of Early Evolution Stage Active Galactic Nuclei

“…Sources on the MS can be divided into two main populations according to the full width at half maximum (FWHM) of their Hβ line. Population A sources are characterized by FWHM <4000 km s −1 , and they often exhibit prominent Fe II emission [27,36,40,[44][45][46]. The origin of blue outliers is still unclear [47][48][49], and it could be connected to the high Eddington ratio observed in population A sources and NLS1s [50][51][52][53].…”