Spectropolarimetry and spectral decomposition of high-accreting Narrow Line Seyfert 1 galaxies

TL;DR

This study uses spectropolarimetry and spectral modeling to investigate the geometry and viewing angles of high-accreting Narrow Line Seyfert 1 galaxies, confirming their high Eddington ratios and analyzing the properties of their scattering media.

Contribution

It applies spectropolarimetric observations and radiative transfer modeling to NLSy1 galaxies, providing new insights into their geometry, viewing angles, and the connection between FeII emission and accretion properties.

Findings

Confirmed high Eddington ratios in the three studied NLSy1 galaxies.

Successfully modeled the Hα line profile in natural and polarized light.

Found that black hole mass and Eddington ratio mainly drive spectral properties.

Abstract

Narrow Line Seyfert 1 (NLSy1) galaxies have been shown to have high Eddington ratios and relatively small black hole masses. The measurement of the black hole masses is based on the virial relation which is dependent on the distribution of the line-emitting gas and the viewing angle to the source. Spectropolarimetry enables us to probe the geometry of this line-emitting gas and allows us to estimate independently the viewing angle of the source by comparing the spectrum viewed under natural light and in the polarized light. We performed spectropolarimetric observations of three NLSy1 - Mrk 1044, SDSS J080101.41+184840.7, and IRAS 04416+1215 using the European Southern Observatory's Very Large Telescope. We use ESO Reflex workflow to perform standard data reduction and extract the natural and polarized spectra. We estimate the Stokes parameters and the viewing angles of the three sources. We model the Stokes parameters and infer the properties of the scattering media - located in the equatorial and polar regions, and simulate the spectra observed both in natural light and in polarized light using the polarization radiative transfer code STOKES. We confirm that all three sources are high Eddington ratio objects. We are successful in recovering the observed H$\alpha$ line profile both in the natural and polarized light using the STOKES modelling. We recover the polarization fractions of the order of 0.2-0.5% for the three sources. Our principal component analysis shows that the sample of the 25 sources including our sources, Fairall 9 from Jiang et al. (2021), and sources from Capetti et al. (2021) are mainly driven by the black hole mass and Eddington ratio. We re-affirm the connection of the strength of the optical FeII emission with the Eddington ratio, but the dependence on the viewing angle is moderate, more like a secondary effect.