Resolving Quiescent Galaxies at z≳2: I. Search for Gravitationally Lensed Sources and Characterization of their Structure, Stellar Populations, and Line Emission

Quiescent galaxies at z ≳ 2 are compact and have weak or absent emission lines, making it difficult to spatially resolve their kinematics and stellar populations using ground-based spectroscopy. Gravitationally lensed examples provide a promising route forward, but such objects are very rare. We describe a search in the fields of 232 galaxy clusters that has uncovered five bright (H AB < 20) lensed galaxies with red near-infrared colors. These include MRG-M0138, which is the brightest lensed galaxy known in the near-infrared. Analysis of near-infrared spectra and multiband photometry confirms that all are quiescent galaxies at z = 1.95–2.64 with stellar ages of 0.5–1.4 Gyr (corresponding to formation epochs z form ≃ 3–4) and stellar masses of 10^11.6-12.8 µ^-1 Mʘ, where μ is the magnification. In three cases, we derive lens models and reconstruct the source structure; these galaxies are massive (M ≳ 10^11.10 Mʘ) and follow the mass–size relation defined by unlensed samples. In two of these three galaxies, the main structural component is an inclined disk. Weak emission lines are detected in four of five galaxies with high ratios [NII]/Hα ≃ 2–6 that are inconsistent with a star formation origin. Based on the line ratios, the Hα equivalent widths, and the distribution and kinematics of the gas, we infer that shocks are likely to be present in at least two galaxies and could be present in all of the line emitters. We speculate that these could be analogs of local galaxies in which AGN jet-driven outflows are thought to heat the interstellar medium and suppress star formation. In further papers, we will present spatially resolved measurements of the stellar populations and kinematics of this unique sample