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Gravitational lenses can magnify distant galaxies, allowing us to discover and characterize the stellar populations of intrinsically faint, quiescent galaxies that are otherwise extremely difficult to directly observe at high redshift from ground-based telescopes. Here, we present the spectral analysis of two lensed, quiescent galaxies atz≳ 1 discovered by theASTRO 3D Galaxy Evolution with Lensessurvey:AGEL1323 (M_*∼ 10^11.1M_⊙,z= 1.016,μ∼ 14.6) andAGEL0014 (M_*∼ 10^11.5M_⊙,z= 1.374,μ∼ 4.3). We measured the age, [Fe/H], and [Mg/Fe] of the two lensed galaxies using deep, rest-frame-optical spectra (S/N ≳40 Å⁻¹) obtained on the Keck I telescope. The ages ofAGEL1323 andAGEL0014 are${5.6}_{-0.8}^{+0.8}$Gyr and${3.1}_{-0.3}^{+0.8}$Gyr, respectively, indicating that most of the stars in the galaxies were formed less than 2 Gyr after the Big Bang. Compared to nearby quiescent galaxies of similar masses, the lensed galaxies have lower [Fe/H] and [Mg/H]. Surprisingly, the two galaxies have comparable [Mg/Fe] to similar-mass galaxies at lower redshifts, despite their old ages. Using a simple analytic chemical evolution model connecting the instantaneously recycled element Mg with the mass-loading factors of outflows averaged over the entire star formation history, we found that the lensed galaxies may have experienced enhanced outflows during their star formation compared to lower-redshift galaxies, which may explain why they quenched early.

We measure the size–luminosity relation of photometrically selected galaxies within the redshift range z ∼ 6–9, using galaxies lensed by six foreground Hubble Frontier Fields (HFF) clusters. The power afforded by strong gravitational lensing allows us to observe fainter and smaller galaxies than in blank fields. We select our sample of galaxies and obtain their properties, e.g. redshift, magnitude, from the photometrically derived ASTRODEEP catalogues. The intrinsic size is measured with the Lenstruction software, and completeness maps are created as a function of size and luminosity via the GLACiAR2 software. We perform a Bayesian analysis to estimate the intrinsic and incompleteness-corrected size–luminosity distribution, with parametrization re ∝ Lβ. We find slopes of $\beta =0.50^{+0.07}_{-0.07}$ at z ∼ 6 − 7 and $\beta =0.67^{+0.14}_{-0.15}$ at z ∼ 8.5, adopting the Bradac lens model. Our inferred slopes are consistent with other independent determinations of the size–luminosity relation from the HFF data set and steeper than that obtained from the bright galaxies in blank fields. We also investigate the systematic uncertainties associated with the choice of lens models, finding that the slopes of size–luminosity relations derived from different models are mutually consistent, i.e. modelling errors are not a significant source of discrepancy between the size–luminosity relation of blank and lensed fields.