The optical emission line spectrum of Mark 110

TL;DR

This study provides a detailed analysis of the emission line spectrum of Mark 110, revealing its physical conditions, emission regions, and suggesting it is a broad-line Seyfert 1 galaxy with unique spectral features.

Contribution

The paper offers the first detailed spectral analysis of Mark 110, identifying multiple emission line systems and clarifying its classification as a BLS1 with specific physical properties.

Findings

Narrow emission lines originate from a region with a density gradient of 10^3-10^6 cm^-3.

Absence of broad Fe II emission lines confirmed.

Mark 110 is likely a BLS1 with relatively narrow broad lines and a high black hole mass.

Abstract

We analyse in detail the rich emission line spectrum of Mark 110 to determine the physical conditions in the nucleus of this object, a peculiar NLS1 without any detectable Fe II emission associated with the broad line region and with a $\lambda5007/H\beta$ line ratio unusually large for a NLS1. We use 24 spectra obtained with the Marcario Low Resolution Spectrograph attached at the prime focus of the 9.2 m Hobby-Eberly telescope at the McDonald observatory. We fitted the spectrum by identifying all the emission lines (about 220) detected in the wavelength range 4200-6900 \AA (at rest). The narrow emission lines are probably produced in a region with a density gradient in the range 10$^{3}-10^{6}$ cm$^{-3}$ with a rather high column density (5$\times10^{21}$ cm$^{-2}$). In addition to a narrow line system, three major broad line systems with different line velocity and width are required. We confirm the absence of broad Fe II emission lines. We speculate that Mark 110 is in fact a BLS1 with relatively "narrow" broad lines but with a BH mass large enough compared to its luminosity to have a lower than Eddington luminosity.