Emergence of a Quasar Outflow

TL;DR

This paper reports the first observation of a high-velocity quasar outflow emerging between 2002 and 2006, characterized by broad absorption lines with unique properties, indicating a dynamic and evolving outflow structure.

Contribution

It presents the first detection of a high-velocity outflow emergence in a luminous quasar, revealing new insights into quasar outflow dynamics and evolution.

Findings

Outflow velocity ~26,300 km/s with broad absorption lines

Lines weakened and narrowed over six years

No evidence of acceleration or slower outflow components

Abstract

We report the first discovery of the emergence of a high-velocity broad-line outflow in a luminous quasar, J105400.40+034801.2 at redshift z ~ 2.1. The outflow is evident in ultraviolet CIV and SiIV absorption lines with velocity shifts v ~ 26,300 km/s and deblended widths FWHM ~ 4000 km/s. These features are marginally strong and broad enough to be considered broad absorption lines (BALs), but their large velocities exclude them from the standard BAL definition. The outflow lines appeared between two observations in the years 2002.18 and 2006.96. A third observation in 2008.48 showed the lines becoming ~40% weaker and 10% to 15% narrower. There is no evidence for acceleration or for any outflow gas at velocities <23,000 km/s. The lines appear to be optically thick, with the absorber covering just 20% of the quasar continuum source. This indicates a characteristic absorber size of ~4 x 10^15 cm, but with a BAL-like total column density log N_H (cm^-2) > 21.2 and average space density n_H > 2 x 10^5 cm^-3. We attribute the emergence of the outflow lines to a substantial flow structure moving across our line of sight, possibly near the ragged edge of the main BAL flow or possibly related to the onset of a BAL evolutionary phase.