Molecular Outflow in the Reionization-epoch Quasar J2054-0005 Revealed by OH 119 μm Observations

<jats:title>Abstract</jats:title> <jats:p>Molecular outflows are expected to play a key role in galaxy evolution at high redshift. To study the impact of outflows on star formation at the epoch of reionization, we performed sensitive Atacama Large Millimeter/submillimeter Array observations of OH 119 <jats:italic>μ</jats:italic>m toward J2054-0005, a luminous quasar at <jats:italic>z</jats:italic> = 6.04. The OH line is detected and exhibits a P-Cygni profile that can be fitted with a broad blueshifted absorption component, providing unambiguous evidence of an outflow, and an emission component at near-systemic velocity. The mean and terminal outflow velocities are estimated to be <jats:italic>v</jats:italic> <jats:sub>out</jats:sub> ≈ 670 and 1500 km s<jats:sup>−1</jats:sup>, respectively, making the molecular outflow in this quasar one of the fastest at the epoch of reionization. The OH line is marginally spatially resolved for the first time in a quasar at <jats:italic>z</jats:italic> > 6, revealing that the outflow extends over the central 2 kpc region. The mass outflow rate is comparable to the star formation rate (<jats:inline-formula> <jats:tex-math> <?CDATA ${\dot{M}}_{\mathrm{out}}/\mathrm{SFR}\sim 2$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mover accent="true"> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>̇</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mi>out</mml:mi> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi>SFR</mml:mi> <mml:mo>∼</mml:mo> <mml:mn>2</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjad0df5ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>), indicating rapid (∼10<jats:sup>7</jats:sup> yr) quenching of star formation. The mass outflow rate in a sample of star-forming galaxies and quasars at 4 < <jats:italic>z</jats:italic> < 6.4 exhibits a positive correlation with the total infrared luminosity, although the scatter is large. Owing to the high outflow velocity, a large fraction (up to ∼50%) of the outflowing molecular gas may be able to escape from the host galaxy into the intergalactic medium.</jats:p>