Early-type Galaxies on the Star Formation Main Sequence: Internal Star Formation Geometry Revealed with MaNGA and Their Environmental Origin

TL;DR

This study uses spatially-resolved data from MaNGA to classify main sequence galaxies into early and late types, revealing diverse internal star formation patterns and environmental influences that suggest different evolutionary pathways.

Contribution

It introduces a detailed classification of MS galaxies based on internal star formation and stellar mass distributions, highlighting the importance of spatially-resolved observations for understanding galaxy evolution.

Findings

MS-early extunderscore SF galaxies have centrally concentrated star formation and are in dense environments.

MS-early extunderscore stellar galaxies have prominent bulges, suppressed central star formation, and are in typical late-type environments.

Spatially-resolved data reveals diverse evolutionary pathways within galaxies with similar global properties.

Abstract

Star-forming galaxies on the main sequence (MS) are often regarded as a uniform population characterized by similar global star formation properties. However, there exists a diversity in galaxy morphologies at fixed stellar mass and SFR. In this study, using spatially-resolved properties from the MaNGA final data release, we classify MS galaxies into late-type (MS-late) and early-type (MS-early). In addition, we further divide the MS-early galaxies into two distinct subgroups based on their internal star formation and stellar mass distributions within the galaxies. The first group -- ``MS-early\_SF'' -- shows centrally concentrated star formation without prominent stellar bulges and resides preferentially in dense environments, suggesting environmentally-driven evolution. The second group -- ``MS-early\_stellar'' -- exhibits significant stellar bulges with suppressed central star formation, maintains disk-like star formation patterns, and inhabits environments similar to those of late-type galaxies, indicating evolution through internal secular processes. Our findings demonstrate that spatially-resolved observations play critical roles in revealing the diverse evolutionary pathways hidden within galaxies that share similar global properties.