2021ApJ...914....7G

We use the Cosmic Assembly Deep Near-infrared Extragalactic Legacy Survey data to study the relationship between quenching and the stellar mass surface density within the central radius of 1 kpc (Σ₁) of low-mass galaxies (stellar mass M_* <= 10^9.5 M_☉) at 0.5 <= z < 1.5. Our sample is mass complete down to ∼10⁹ M_☉ at 0.5 <= z < 1.0. We compare the mean Σ₁ of star-forming galaxies (SFGs) and quenched galaxies (QGs) at the same redshift and M_*. We find that low-mass QGs have a higher Σ₁ than low-mass SFGs, similar to galaxies above 10¹⁰ M_☉. The difference of Σ₁ between QGs and SFGs increases slightly with M_* at M_* <= 10¹⁰ M_☉ and decreases with M_* at M_* >= 10¹⁰ M_☉. The turnover mass is consistent with the mass where quenching mechanisms transition from internal to environmental quenching. At 0.5 <= z < 1.0, we find that Σ₁ of galaxies increases by about 0.25 dex in the green valley (i.e., the transition region from star forming to fully quenched), regardless of their M_*. Using the observed specific star formation rate gradient in the literature as a constraint, we estimate that the quenching timescale (i.e., time spent in the transition) of low-mass galaxies is a few (∼4) Gyr at 0.5 <= z < 1.0. The mechanisms responsible for quenching need to gradually quench star formation in an outside-in way, i.e., preferentially ceasing star formation in outskirts of galaxies while maintaining their central star formation to increase Σ₁. An interesting and intriguing result is the similarity of the growth of Σ₁ in the green valley between low-mass and massive galaxies, which suggests that the role of internal processes in quenching low-mass galaxies is a question worthy of further investigation.