A Compact Early-type Galaxy at z = 0.6 Under a Magnifying Lens: Evidence For Inside-out Growth

TL;DR

This study uses gravitational lensing and adaptive optics to examine a compact, early-type galaxy at z=0.63, providing insights into its structure and potential inside-out growth mechanisms.

Contribution

It presents high-resolution imaging of a lensed early-type galaxy at intermediate redshift, revealing detailed sub-kpc structures and a two-component surface brightness profile.

Findings

Galaxy is massive and compact with a two-component structure.

Extended component may be from evolved 'red nuggets' or already present at high redshift.

Effective resolution of ~200 pc achieved through lensing and adaptive optics.

Abstract

We use Keck laser guide star adaptive optics imaging and exploit the magnifying effects of strong gravitational lensing (the effective resolution is FWHM ~ 200 pc) to investigate the sub-kpc scale of an intermediate-redshift (z = 0.63) massive early-type galaxy being lensed by a foreground early-type galaxy; we dub this class of strong gravitational lens systems EELs, e.g., early-type/early-type lenses. We find that the background source is massive (M* = 10^{10.9} M_sun) and compact (r_e = 1.1 kpc), and a two-component fit is required to model accurately the surface brightness distribution, including an extended low-surface-brightness component. This extended component may arise from the evolution of higher-redshift `red nuggets' or may already be in place at z ~ 2 but is unobservable due to cosmological surface brightness dimming.