4.7 Article

The complex stellar system M 22: confirming abundance variations with high precision differential measurements

Journal

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 516, Issue 3, Pages 3515-3531

Publisher

OXFORD UNIV PRESS
DOI: 10.1093/mnras/stac2254

Keywords

techniques: spectroscopic; stars: abundances; stars: Population II; globular clusters: general; globular clusters: individual: NGC 6656

Funding

  1. Australian Government Research Training Program (RTP) Scholarship
  2. Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D) [CE170100013]
  3. NASA Astrophysics Data Analysis Program [80NSSC21K0627]
  4. United States National Science Foundation [PHY 14-30152, AST 1613536, AST 1815403/1815767]
  5. European Research Council under the European Union [716082]
  6. MIUR through the FARE project [R164RM93XW]
  7. PRIN program [2017Z2HSMF]
  8. European Research Council (ERC) [716082] Funding Source: European Research Council (ERC)

Ask authors/readers for more resources

High-quality VLT/UVES spectra of six red giant branch stars in M22 reveal variations in abundance of elements such as Fe, Na, and Si. The study suggests that M22 hosts two stellar populations with abundance differences, possibly indications of a nuclear star cluster, merged clusters, or an original building block of the Milky Way.
M 22 (NGC 6656) is a chemically complex globular cluster-like system reported to harbour heavy element abundance variations. However, the extent of these variations and the origin of this cluster is still debated. In this work, we investigate the chemical in-homogeneity of M 22 using differential line-by-line analysis of high-quality (R = 110 000, S/N = 300 per pixel at 514 nm) VLT/UVES spectra of six carefully chosen red giant branch stars. By achieving abundance uncertainties as low as similar to 0.01 dex (similar to 2 per cent), this high precision data validates the results of previous studies and reveals variations in Fe, Na, Si, Ca, Sc, Ti, Cr, Mn, Co, Ni, Zn, Y, Zr, La, Ce, Nd, Sm, and Eu. Additionally, we can confirm that the cluster hosts two stellar populations with a spread of at least 0.24 dex in [Fe/H] and an average s-process abundance spread of 0.65 dex. In addition to global variations across the cluster, we also find non-negligible variations within each of the two populations, with the more metal-poor population hosting larger spreads in elements heavier than Fe than the metal-rich. We address previous works that do not identify anomalous abundances and relate our findings to our current dynamical understanding of the cluster. Given our results, we suggest that M 22 is either a nuclear star cluster, the product of two merged clusters, or an original building block of the Milky Way.

Authors

I am an author on this paper
Click your name to claim this paper and add it to your profile.

Reviews

Primary Rating

4.7
Not enough ratings

Secondary Ratings

Novelty
-
Significance
-
Scientific rigor
-
Rate this paper

Recommended

No Data Available
No Data Available