Low-metallicity globular clusters in the low-mass isolated spiral galaxy NGC 2403
Abstract
The globular cluster (GC) systems of low-mass late-type galaxies, such as NGC 2403, have been poorly studied to date. As a low mass galaxy (M* = 7 × 109 M⊙), cosmological simulations predict NGC 2403 to contain few, if any, accreted GCs. It is also isolated, with a remarkably undisturbed HI disc. Based on candidates from the literature, Sloan Digital Sky Survey and Hyper Suprime-Cam imaging, we selected several GCs for follow-up spectroscopy using the Keck Cosmic Web Imager. From their radial velocities and other properties, we identify eight bona-fide GCs associated with either the inner halo or the disc of this bulgeless galaxy. A stellar population analysis suggests a wide range of GC ages from shortly after the big bang until the present day. We find all of the old GCs to be metal-poor with [Fe/H] ≤ -1. The age-metallicity relation for the observed GCs suggests that they were formed over many Gyr from gas with a low effective yield, similar to that observed in the SMC. Outflows of enriched material may have contributed to the low yield. With a total system of ~50 GCs expected, our study is the first step in fully mapping the star cluster history of NGC 2403 in both space and time.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- May 2022
- DOI:
- 10.1093/mnras/stac503
- arXiv:
- arXiv:2202.10539
- Bibcode:
- 2022MNRAS.512..802F
- Keywords:
-
- galaxies: evolution;
- galaxies: individual: NGC 2403;
- galaxies: star clusters;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 9 pages, 7 figures, accepted for publication in MNRAS