Black Hole Mass Estimation in Type 1 AGN: H$\beta$ vs. Mg II lines and the role of Balmer continuum

TL;DR

This study compares Hβ and Mg II spectral lines for black hole mass estimation in Type 1 AGN, highlighting the reliability of Hβ and the impact of Balmer continuum emission on mass overestimation.

Contribution

It demonstrates that Hβ is a more reliable virial estimator than Mg II and quantifies how Balmer continuum emission can cause overestimation of black hole mass.

Findings

Hβ line is a more confident virial estimator than Mg II.

Balmer continuum emission can lead to ~5% overestimation of black hole mass.

Mg II shows less virialization confidence compared to Hβ.

Abstract

Here we investigate the H$\beta$ and Mg II spectral line parameters used for the black hole mass (M$_{\rm BH}$) estimation for a sample of Type 1 Active Galactic Nuclei (AGN) spectra selected from the Sloan Digital Sky Survey (SDSS) database. We have analyzed and compared the virialization of the H$\beta$ and Mg II emission lines, and found that the H$\beta$ line is more confident virial estimator than Mg II. We have investigated the influence of the Balmer continuum emission to the M$_{\rm BH}$ estimation from the UV parameters, and found that the Balmer continuum emission can contribute to the overestimation of the M$_{\rm BH}$ on average for ~ 5% (up to 10%).