# The physical constraints on a new LoBAL QSO at z=4.82

## TL;DR

This study characterizes a high-redshift LoBAL QSO at z=4.82, revealing strong outflows and high Eddington ratio, providing insights into early quasar feedback mechanisms and black hole growth.

## Contribution

It provides the first detailed physical analysis of a high-redshift LoBAL QSO, including black hole mass, outflow properties, and feedback implications.

## Key findings

- Confirmed the LoBAL nature with new redshift at 4.82
- Estimated black hole mass of approximately 2.3 billion solar masses
- Derived significant outflow kinetic power exceeding 0.9% of Eddington luminosity

## Abstract

Very few low-ionization broad absorption line (LoBAL) QSOs have been found at high redshifts to date. One high-redshift LoBAL QSO, J0122+1216, was recently discovered at the Lijiang 2.4-m Telescope with an initial redshift determination of 4.76. Aiming to investigate its physical properties, we carried out follow-up observations in the optical and near-IR spectroscopy. Near-IR spectra from UKIRT and P200 confirms that it is a LoBAL, with a new redshift determination of $4.82\pm0.01$ based on the \mgii~ emission-line. The new \mgii~ redshift determination reveals strong blueshifts and asymmetry of the high-ionization emission lines. We estimated a black hole mass of $\sim 2.3\times 10^9 M_\odot$ and Eddington ratio of $\sim 1.0$ according to the empirical \mgii-based single-epoch relation and bolometric correction factor. It is possible that strong outflows are the result of an extreme quasar environment driven by the high Eddington ratio. A lower limit on the outflowing kinetic power ($>0.9\% L_{Edd}$) was derived from both emission and absorption lines, indicating these outflows play a significant role in the feedback process to regulate the growth of its black hole as well as host galaxy evolution.