Environmental effects as a key factor in shaping star-forming S0 galaxies

¹ Department of Astronomy, Xiamen University, Xiamen, Fujian 361005, China
² Department of Astronomy, Nanjing University, Nanjing 210093, China
³ School of Astronomy and Space Science, Nanjing University, Nanjing 210023, China
⁴ Key Laboratory of Modern Astronomy and Astrophysics, Nanjing University, Nanjing 210023, China

^⋆ Corresponding author; jfwang@xmu.edu.cn

Received: 24 June 2024
Accepted: 1 September 2024

Abstract

Context. The origins of lenticular galaxies (S0s) can be classified into two main categories: “minor mergers” in low-density environments (LDEs) and “faded spirals” in high-density environments (HDEs). The transitional phase in the evolution of S0s, namely, star-forming lenticular galaxies (SFS0s), can serve as an important probe for analyzing the complex processes involved in the transformation between different galaxy types and the quenching of star formation (SF).

Aims. We attempt to find the impact of different environments on the global properties and spatially resolved quantities of SFS0s.

Methods. We selected 71 SFS0s from the SDSS-IV MaNGA Survey, comprising 23 SFS0s in HDEs (SFS0s_HE) and 48 SFS0s in LDEs (SFS0s_LE). We examined the effects of the environment, by studying the global properties, concentration index, and radial profiles of the derived quantities.

Results. The varied environments of SFS0s do not lead to any significant difference in global properties (e.g., Sérsic index). By calculating CI_Hα/cont, we observe that different environments may cause varying concentrations of SF. Specifically, SFS0s_LE, affected by external gas mergers or inflow, exhibit a more centrally concentrated SF (i.e., larger CI_Hα/cont). This trend is further supported by CI_SFR, Hα, which only considers the gas disk of the galaxy. This observation is aligned with the observed shrinking of gas disks in galaxies affected by ram-pressure stripping in HDEs. Furthermore, their Σ_SFR or resolved sSFR are comparable. On average, SFS0s_LE display significantly higher values for both quantities. Finally, the observed D_n4000 and gas-phase metallicity gradient correspond well to their assumed origins. However, we did not find a significantly lower gas-phase metallicity in SFS0s_LE.

Conclusions. We suggest that different environments (i.e., origins) do not have a significant impact on the global properties of SFS0s, but they do indeed affect the distribution of SF. Considering the size of our sample and the unique nature of the galaxy, additional atomic and molecular gas data may provide further details to improve our understanding of these systems.