Strong Response of the very broad h$\beta$ Emission Line in Luminous Radio-Quite Quasar pg1416-129

TL;DR

This study presents spectroscopic observations of quasar PG 1416-129, revealing strong variability in the broad Hβ emission line and challenging existing models of emission-line regions.

Contribution

It provides new high-quality spectra over a decade, analyzing the variability of broad Balmer lines and questioning the necessity of an optically thin inner emission region.

Findings

Strong response of very broad Hβ component to continuum changes

Significant variations in velocity, FWHM, and flux of broad components

Flat Balmer decrements at line wings challenge optically thin models

Abstract

We report new spectroscopic observations performed in 2010 and 2011 for luminous radio-quite quasar PG 1416-129. Our new spectra with high quality cover both H$\beta$ and H$\alpha$ regions, and show negligible line profile variation within a timescale of one year. The two spectra allow us to study the variability of the Balmer line profile by comparing the spectra with the previous ones taken at 10 and 20 years ago. By decomposing the broad Balmer emission lines into two Gaussian profiles, our spectral analysis suggests a strong response to the continuum level for the very broad component, and significant variations in both bulk blueshift velocity/FWHM and flux for the broad component. The new observations additionally indicate flat Balmer decrements (i.e., too strong H$\beta$ emission) at the line wings, which is hard to be reproduced by recent optically thin models. With these observations we argue that a separate inner optically thin emission-line region might not be necessary in the object to reproduce the observed line profiles.