[O iii] λ5007 emissions in extremely red quasars (ERQs) are compact

Abstract

ABSTRACT ‘Extremely red quasars’ (ERQs) are a non-radio-selected, intrinsically luminous population of quasars at cosmic noon selected by their extremely red colour from rest-frame UV to mid-IR. ERQs are uniquely associated with exceptionally broad and blueshifted [O iii] $\lambda$5007 emission reaching speeds $\gt $6000 km s$^{-1}$. We obtained adaptive optics integral-field spectroscopic observations using Keck/OSIRIS and Gemini/NIFS of a sample of 10 ERQs with bolometric luminosities (10$^{47.0}$–10$^{47.9}$) erg s$^{-1}$ at $z\sim$ (2.3–3.0). The goal is to measure the sizes and spatially resolved kinematics of the [O iii]-emitting regions. We study the surface brightness maps and aperture-extracted spectra and model the point-spread functions. We identify signs of merger activities in the continuum emissions. We identify physically distinct [O iii] kinematic components that are bimodal and respectively trace ERQ-driven outflows of velocity dispersion $\gtrsim$250 km s$^{-1}$ and dynamically quiescent interstellar media. We find that the ERQ-driven ionized outflows are typically at $\sim$1 kpc scales whereas the quiescent ionized gas extend to a few kpc. Compared to normal quasars the extremely fast ERQ-driven [O iii] outflows tend to be more compact, supporting the notion that ERQs are in a young stage of quasar/galaxy evolution and represent unique physical conditions beyond orientation differences with normal quasar populations. The kinematically quiescent [O iii] emissions in ERQs tend to be spatially resolved but less extended than in normal quasars, which can be explained by global and patchy dust obscuration. The hint of ionization cones suggests some of the obscuration can be partially explained by a patchy torus.