The star formation history of low-mass disk galaxies: A case study of NGC 300

¹ Yunnan Observatories, Chinese Academy of Sciences, 650011 Kunming, PR China
e-mail: kxyysl@ynao.ac.cn
² Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, 650011 Kunming, PR China
³ University of Chinese Academy of Sciences, 100049 Beijing, PR China
⁴ Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, 200030 Shanghai, PR China

Received: 23 July 2015
Accepted: 13 October 2015

Abstract

Context. Since NGC 300 is a bulgeless, isolated low-mass galaxy and it has not experienced radial migration during its evolution history, it can be treated as an ideal laboratory to test the simple galactic chemical evolution model.

Aims. Our main aim is to investigate the main properties of the star formation history (SFH) of NGC 300 and compare its SFH with that of M 33 to explore the common properties and differences between these two nearby low-mass systems.

Methods. We construct a simple chemical evolution model for NGC 300, assuming its disk forms gradually from continuous accretion of primordial gas and including the gas-outflow process. The model allows us to build a bridge between the SFH and observed data of NGC 300, in particular, the present-day radial profiles and global observed properties (e.g., cold gas mass, star formation rate, and metallicity). By means of comparing the model predictions with the corresponding observations, we adopt the classical χ² methodology to find out the best combination of free parameters a, b, and b_out.

Results. Our results show that by assuming an inside-out formation scenario and an appropriate outflow rate, our model reproduces well most of the present-day observational values. The model not only reproduces well the radial profiles, but also the global observational data for the NGC 300 disk. Our results suggest that NGC 300 may experience a rapid growth of its disk. Through comparing the best-fitting, model-predicted SFH of NGC 300 with that of M 33, we find that the mean stellar age of NGC 300 is older than that of M 33 and there is a recent lack of primordial gas infall onto the disk of NGC 300. Our results also imply that the local environment may play a key role in the secular evolution of galaxy disks.