Probing the He II re-Ionization ERa via Absorbing C IV Historical Yield (HIERACHY) I: A Strong Outflow from a z~4.7 Quasar

TL;DR

This study reports a powerful high-velocity outflow in a z~4.7 quasar, characterized by blueshifted emission lines and absorption features, providing insights into early quasar feedback mechanisms.

Contribution

It presents the first detailed high-resolution UV spectrum analysis of a z~4.7 quasar revealing extreme outflow velocities and ionization trends, advancing understanding of quasar outflows in the early universe.

Findings

C IV line blueshifted at -6500 km/s, among the highest at z > 4

Higher ionization lines are broader and more blueshifted

Multiple absorption components suggest complex outflow or intervening systems

Abstract

Outflows from super-massive black holes (SMBHs) play an important role in the co-evolution of themselves, their host galaxies, and the larger scale environments. Such outflows are often characterized by emission and absorption lines in various bands and in a wide velocity range blueshifted from the systematic redshift of the host quasar. In this paper, we report a strong broad line region (BLR) outflow from the z~4.7 quasar BR 1202-0725 based on the high-resolution optical spectrum taken with the Magellan Inamori Kyocera Echelle (MIKE) spectrograph installed on the 6.5m Magellan/Clay telescope, obtained from the `Probing the He II re-Ionization ERa via Absorbing C IV Historical Yield' (HIERACHY) project. This rest-frame ultraviolet (UV) spectrum is characterized by a few significantly blueshifted broad emission lines from high ions; the most significant one is the C IV line at a velocity of -6500 km/s relative to the H{\alpha} emission line, which is among the highest velocity BLR outflows in observed quasars at z > 4. The measured properties of UV emission lines from different ions, except for O I and Ly{\alpha}, also follow a clear trend that higher ions tend to be broader and outflow at higher average velocities. There are multiple C IV and Si IV absorbing components identified on the blue wings of the corresponding emission lines, which may be produced by either the outflow or the intervening absorbers.