Journal Talk 19: Imtiaz et al. (2026 (expected))

Resolved Metallicity and Age Gradients in the Lensed Quiescent Galaxy AGEL0014 at z ≈ 1.4.

[Based on research done under supervision of Dr. Nicha Leethochawalit, Researcher at National Astronomical Research Institute of Thailand (NARIT)]

Abstract

The formation and quenching mechanisms of massive galaxies at high redshift remain a focal point of galaxy evolution studies. We present a spatially resolved stellar population analysis of the lensed quiescent galaxy AGEL0014 (z ≈ 1.4) to constrain its formation history. Combining HST (F814W ), Gemini/GSAOI (H, J, Ks), and Keck/MOSFIRE (J,Y ) data, we modeled the system using Lenstronomy. To robustly recover intrinsic stellar population trends given the seeing (≈ 0.4′′), we forward-modeled source plane metallicity gradients, applying light-weighting and PSF convolution to the projected image-plane map to simulate slit data. Full spectrum fitting with the alf (Absorption Line Fitter) code reveals a clear positive age gradient and a negative metallicity gradient. The central region exhibits log(Age/Gyr) = 0.37 ± 0.05 and [Z/H] = −0.31 ± 0.11, while the outer region hosts an older population with log(Age/Gyr) = 0.49 ± 0.07 and [Z/H] = −0.53 ± 0.10. Interestingly, [Fe/H] increases from 0.01 ± 0.11 in the core to 0.19 ± 0.10 in the periphery. These signatures support an outside-in quenching scenario: the high α-enrichment in the core suggests it formed in a short, intense burst and quenched abruptly, whereas the iron-rich outskirts imply a more extended star formation history allowing for enrichment from Type Ia progenitors.

Link: https://docs.google.com/presentation/d/1plgX7tQJdRSfYA3rwAsktoAbKSD9Am6z/edit?usp=sharing

Presenter: Ahmad Al-Imtiaz (Graduate Research Assistant at CASSA; M.Sc. in Physics from Shahjalal University of Science & Technology)

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