First Evidence of Globular Cluster Formation from the Ejecta of Prompt Type Ia Supernovae

TL;DR

This paper presents the first evidence that globular clusters can form from the ejecta of prompt Type Ia supernovae, supported by spectroscopic data and chemical abundance analysis of a specific cluster in the Large Magellanic Cloud.

Contribution

It introduces a novel formation scenario for globular clusters involving SNe Ia ejecta and metal-poor gas, supported by observational evidence and chemical modeling.

Findings

NGC 1718 formed from SNe Ia ejecta and metal-poor gas

Observed low [Mg/Fe] ratio consistent with SNe Ia enrichment

Outer LMC disk may contain stars formed through similar processes

Abstract

Recent spectroscopic observations of globular clusters (GCs) in the Large Magellanic Cloud (LMC) have discovered that one of the intermediate-age GC, NGC 1718 with [Fe/H]=-0.7 has an extremely low [Mg/Fe] ratio of ~-0.9. We propose that NGC 1718 was formed from the ejecta of type Ia supernovae (SNe Ia) mixed with very metal-poor ([Fe/H] <-1.3) gas about ~ 2 Gyr ago. The proposed scenario is shown to be consistent with the observed abundances of Fe-group elements such as Cr, Mn, and Ni. In addition, compelling evidence for asymptotic giant branch stars playing a role in chemical enrichment during this GC formation is found. We suggest that the origin of the metal-poor gas is closely associated with the efficient gas-transfer from the outer gas disk of the Small Magellanic Cloud to the LMC disk. We anticipate that the outer part of the LMC disk contains field stars exhibiting significantly low [Mg/Fe] ratios, formed through the same process as NGC 1718.