PGC 44685: A Dwarf Star-forming Lenticular Galaxy with Wolf-Rayet Population

TL;DR

This study investigates a dwarf star-forming lenticular galaxy, PGC 44685, revealing active star formation, Wolf-Rayet stars, and low metallicity regions, providing insights into S0 galaxy evolution in the field.

Contribution

It presents the first detailed spatially resolved analysis of a dwarf S0 galaxy with active star formation and Wolf-Rayet populations, highlighting complex star formation processes in low-mass, low-metallicity environments.

Findings

Detection of Wolf-Rayet stars in the galaxy

Active star formation with gas depletion timescale <25 Myr

Low metallicity suggests minor accretion of metal-poor gas

Abstract

Lenticular galaxies (S0s) are formed mainly from the gas stripping of spirals in the cluster. But how S0s form and evolve in the field is still untangled. Based on spatially resolved observations from the optical Hispanic Astronomical Center in Andalusia 3.5-m telescope with the PPAK Integral Field Spectroscopy instrument and NOrthern Extended Millimeter Array, we study a dwarf (M*<10^9 Msun) S0, PGC 44685, with triple star-forming regions in the central region, namely A, B, and C, respectively. In northwest region C, we clearly detect the spectral features of Wolf-Rayet (WR) stars and quantify the WR population by stacking spectra with high WR significance. Most of the molecular gas is concentrated in the region C(WR), and there is diffuse gas around regions A and B. The WR region possesses the strongest intensities of Ha, CO(1-0), and 3mm continuum, indicating its ongoing violent star formation (gas depletion timescale $\lesssim$25 Myr) with tentative hundreds (<500) km/s stellar winds accompanied by the WR phase. Most (~96%) of three star-forming regions show relatively low metallicity distributions, suggesting possible (minor) accretions of metal-poor gas that trigger the subsequent complex star formation in a field S0 galaxy. We speculate that PGC 44685 will become quiescent in less than 30 Myr if there is no new molecular gas to provide raw materials for star formation. The existence of this dwarf star-forming S0 presents an example of star formation in the low-mass/metallicity S0 galaxy.