Testing the AGN Paradigm, Part I: a generic SED for Seyfert 1 galaxies

TL;DR

This study tests the Unification Paradigm of AGN by deriving a generic SED for a large sample of Seyfert 1 galaxies using X-CIGALE and constraining the LOS viewing angle. The analysis finds that a clumpy torus with a small viewing angle $i \sim 10^\circ$ describes about 90% of Sy1 galaxies, supporting UPAGN and implying that Sy1N cannot be explained by intermediate LOS angles alone. It reveals new connections between accretion, BLR gas supply, and AGN winds: wind episodes appear triggered by rapid BLR inflows and subsequently replenish the torus, making wind-driven torus formation recurrent. The results further suggest an evolutionary sequence in which Sy1 galaxies with winds are at an earlier phase and gradually transition to wind-less Sy1 while preserving the torus as a relic of past activity, with implications for the role of AGN winds in galaxy formation and growth. The paper also sets up Part II to apply the generic Sy1 SED to a large Sy2 sample to directly test UPAGN across the obscured population.

Abstract

This article presents the first part of a study aimed at testing the unification paradigm for AGN (UPAGN) using the SED reconstruction code X-CIGALE. Our method consists in obtaining a generic SED for a large sample of Seyfert 1 (Sy1; part 1), then applying this SED to Seyfert 2 (Sy2; Part~II), expecting that the only difference will be the line-of-sight (LOS) angle, $i$, relative to the polar axis of the torus of gas and dust obscuring the broad line regions (BLRs). Our sample is composed of 3,896 Type 1, Sy1 at low redshifts, $ z<0.4$, separated into four spectral subgroups depending on the presence or absence in their spectra of narrow emission lines, Sy1N/Sy1B, and AGN wind, Sy1Bw and Sy1Nw. The generic SED produced by X-CIGALE applies to 90\% of the Sy1 in our sample. It includes a clumpy torus with an AGN engine seen face-on ($i \sim 10^\circ \pm 5^\circ$). Our analysis not only supports the existence of a torus in Sy1, in good agreement with UPAGN, but also reveals new facts about the accretion of matter and AGN wind: 1- a sudden accretion of matter from the BLR to the accretion disk triggered the wind, 2- matter from the wind replenishes the torus, consistent with a gradual formation of this structure by recurrent AGN winds, and 3- Sy1Bw and Sy1Nw eventually evolve as AGN without wind, leaving behind a torus as evidence of a higher AGN activity in their past.

Figures (16)

• Figure 1: Density distributions in $z$ in the four spectral subgroups in the two samples SW and SW2M.
• Figure 2: Illustration of the angles as defined in X-CIGALE: $i =$ LOS angle (when $i = 0$, torus viewed face-on) and $oa$ = half-opening angle. In 2012Stalevski, $i = \theta$, $oa = \Theta/2$. Torus and BLR not to scale.
• Figure 3: Box-whisker plots of $\chi^2$ applying the generic SED for Sy1 on galaxies in the samples SW (upper panel) and SW2M (lower panel). The sizes of the boxes are determined by the quartiles, Q1, Q2 and Q3, respectively, $q_n(0.25)$, $q_n(0.50)$ and $q_n(0.75)$, the whiskers being at $\pm 1.5\times IRQ$, where $IRQ = Q3-Q1$, the inter quartile range. All data with values lower/higher that the whiskers are considered outliers.
• Figure 4: Box-whisker plots for i as produced by the Sy1 generic SED on galaxies in the sample SW.
• Figure 5: Comparing results produced by X-CIGALE for the best SEDs in the SW sample at lower $z$ (bin 1, $\Delta z = [0.05 - 0.10)$): Upper panels, left = Sy1B, right = Sy1N, lower panels, left = Sy1Bw, right = Sy1Nw.