Clues to inside-out quenching in quiescent galaxies at $1.2lesssim zlesssim2.2$: age, Fe-, and Mg-abundance gradients from JWST-SUSPENSE

Clues to inside-out quenching in quiescent galaxies at $1.2lesssim zlesssim2.2$: age, Fe-, and Mg-abundance gradients from JWST-SUSPENSE
Chloe M. Cheng, Martje Slob, Mariska Kriek, Aliza G. Beverage, Guillermo Barro, Rachel Bezanson, Anna de Graaff, Natascha M. F"orster Schreiber, Brian Lorenz, Danilo Marchesini, Ignacio Mart’in-Navarro, Adam Muzzin, Andrew B. Newman, Sedona H. Price, Katherine A. Suess, Arjen van der Wel, Jesse van de Sande, Pieter G. van Dokkum, Daniel R. Weisz
arXiv:2509.12316v2 Announce Type: replace
Abstract: [Abridged] Spatially resolved stellar populations of massive quiescent galaxies at cosmic noon provide powerful insights into quenching and stellar mass assembly mechanisms. Previous photometric studies have revealed that the these galaxies’ cores are redder than their outskirts. However, spectroscopy is needed to break the age-metallicity degeneracy and uncover the driver of these colour gradients. Here, we derive age and abundance gradients for 8 distant ($1.2lesssim zlesssim 2.2$) massive ($10.3lesssimlog({rm M}_*/{rm M}_odot)lesssim 11.1$) quiescent galaxies, by fitting full-spectrum models to ultra-deep NIRSpec-MSA spectroscopy from JWST-SUSPENSE. We find that these galaxies have negative age and flat [Fe/H] gradients, with tentative indications of positive [Mg/H] and [Mg/Fe] gradients. These results suggest that galaxy cores are older and perhaps also Mg-deficient compared to galaxy outskirts. The age gradients may indicate inside-out quenching, while Mg-deficient cores could suggest rapid gas expulsion as the central quenching mechanism. Thus, galaxy cores may have formed faster and quenched more efficiently than their outskirts. In this scenario, our [Fe/H] and [Mg/Fe] gradients are still puzzling, and further investigation is required to understand the nature of [Mg/H] gradients in galaxies at these redshifts. Our results contrast lower-z studies, which find flat age and [Mg/Fe] gradients and negative metallicity gradients. Additionally, we find a positive trend between age gradients and rotational support, and marginal trends between [Fe/H] gradients and galaxy velocity dispersions and ages. We discuss our findings in the context of galaxy growth scenarios, including minor mergers and progenitor bias. With this work, we present the first stellar population gradients from NIRSpec-MSA spectroscopy in the largest current sample of distant quiescent galaxies.arXiv:2509.12316v2 Announce Type: replace
Abstract: [Abridged] Spatially resolved stellar populations of massive quiescent galaxies at cosmic noon provide powerful insights into quenching and stellar mass assembly mechanisms. Previous photometric studies have revealed that the these galaxies’ cores are redder than their outskirts. However, spectroscopy is needed to break the age-metallicity degeneracy and uncover the driver of these colour gradients. Here, we derive age and abundance gradients for 8 distant ($1.2lesssim zlesssim 2.2$) massive ($10.3lesssimlog({rm M}_*/{rm M}_odot)lesssim 11.1$) quiescent galaxies, by fitting full-spectrum models to ultra-deep NIRSpec-MSA spectroscopy from JWST-SUSPENSE. We find that these galaxies have negative age and flat [Fe/H] gradients, with tentative indications of positive [Mg/H] and [Mg/Fe] gradients. These results suggest that galaxy cores are older and perhaps also Mg-deficient compared to galaxy outskirts. The age gradients may indicate inside-out quenching, while Mg-deficient cores could suggest rapid gas expulsion as the central quenching mechanism. Thus, galaxy cores may have formed faster and quenched more efficiently than their outskirts. In this scenario, our [Fe/H] and [Mg/Fe] gradients are still puzzling, and further investigation is required to understand the nature of [Mg/H] gradients in galaxies at these redshifts. Our results contrast lower-z studies, which find flat age and [Mg/Fe] gradients and negative metallicity gradients. Additionally, we find a positive trend between age gradients and rotational support, and marginal trends between [Fe/H] gradients and galaxy velocity dispersions and ages. We discuss our findings in the context of galaxy growth scenarios, including minor mergers and progenitor bias. With this work, we present the first stellar population gradients from NIRSpec-MSA spectroscopy in the largest current sample of distant quiescent galaxies.