A broad perspective on multiple abundance populations in the globular cluster NGC 1851

TL;DR

This study analyzes multiple stellar populations in globular cluster NGC 1851 using spectral indices and elemental abundances, revealing four distinct populations with different chemical signatures and confirming extratidal stars' association.

Contribution

It provides a detailed chemical characterization of multiple populations in NGC 1851 using both low-resolution spectra and elemental abundance analysis, highlighting the cluster's complex formation history.

Findings

Identified four distinct stellar populations based on CN and CH indices.

Confirmed chemical differences between primordial and second-generation stars.

Linked barium abundance to CN strength and identified extratidal stars.

Abstract

We present an analysis of the multiple stellar populations of the globular cluster NGC 1851. We used lower resolution spectra of giant stars to measure CN, CH, and calcium H & K spectral indices, and determine elemental abundances for carbon and nitrogen. The CN and CH indices were used to confirm that there are four populations of stars in the cluster. The primordial population of stars, with the lowest CN, was found to be generally chemically distinct in elemental abundances from the second generation populations. As expected, [N/Fe] increases with increasing CN strength, but the only other element that correlated with CN was barium. The two largest populations of stars were found to have the same rate of carbon astration as the stars ascend the giant branch. We were also able to confirm that four previously identified extratidal stars are chemically associated with the cluster. This work shows the benefit of considering the chemistry of globular clusters with both high- and low-resolution spectra.