Spatially resolved signature of quenching in star-forming galaxies

TL;DR

This study uses spatially resolved data from IFU observations to identify recent quenching regions in star-forming galaxies, revealing that quenching occurs between 0.5 and 1.1 effective radii and involves complex processes beyond simple inside-out models.

Contribution

It introduces a new spatial analysis of recent quenching in galaxies using IFU data, challenging the simple inside-out quenching paradigm.

Findings

Quenching regions are located between 0.5 and 1.1 effective radii.

Quenching regions occupy 15% to 45% of galaxy area.

Star formation rate surface density is systematically lower and flatter in quenched galaxies.

Abstract

Understanding when, how and where star formation ceased (quenching) within galaxies is still a critical subject in galaxy evolution studies. Taking advantage of the new methodology developed by Quai et al. (2018) to select recently quenched galaxies, we explored the spatial information provided by IFU data to get critical insights on this process. In particular, we analyse 10 SDSS-IV MaNGA galaxies that show regions with low [O III]/H{\alpha} compatible with a recent quenching of the star formation. We compare the properties of these 10 galaxies with those of a control sample of 8 MaNGA galaxies with ongoing star formation in the same stellar mass, redshift and gas-phase metallicity range. The quenching regions found are located between 0.5 and 1.1 effective radii from the centre. This result is supported by the analysis of the average radial profile of the ionisation parameter, which reaches a minimum at the same radii, while the one of the star-forming sample shows an almost flat trend. These quenching regions occupy a total area between 15\% and 45\% of our galaxies. Moreover, the average radial profile of the star formation rate surface density of our sample is lower and flatter than that of the control sample, at any radii, suggesting a systematic suppression of the star formation in the inner part of our galaxies. Finally, the radial profile of gas-phase metallicity of the two samples have a similar slope and normalisation. Our results cannot be ascribed to a difference in the intrinsic properties of the analysed galaxies, suggesting a quenching scenario more complicated than a simple inside-out quenching.