Optical Spectroscopy of Four Young Radio Sources

TL;DR

This study presents optical spectroscopy of four young radio sources, revealing their similarity to narrow-line Seyfert 1 galaxies in emission features and suggesting they are high black hole mass counterparts of steep-spectrum radio-loud NLS1s.

Contribution

First optical spectroscopic analysis of these young radio sources, establishing their NLS1-like properties and proposing their relation to high mass black hole NLS1s.

Findings

Young radio sources exhibit strong Fe II emission and weak [O III] lines.

Their Eddington ratios are comparable to NLS1 galaxies.

The broad Hβ line is broader than in typical NLS1s, indicating higher black hole masses.

Abstract

We report the optical spectroscopy of four young radio sources which are observed with the Lijiang 2.4m telescope. The Eddington ratios of these sources are similar with those of narrow-line Seyfert 1 galaxies (NLS1s). Their Fe {\sc ii} emission is strong while [O {\sc iii}] strength is weak. These results confirm the NLS1 features of young radio sources, except that the width of broad H$\beta$ of young radio sources is larger than that of NLS1s. We thus suggest that the young radio sources are the high black hole mass counterparts of steep-spectrum radio-loud NLS1s. In addition, the broad H$\beta$ component of \astrobj{4C 12.50} is the blue wing of the narrow component, but not from the broad line region.