The chemical compositions of multiple stellar populations in the globular cluster NGC 2808
Date Issued
2022
Author(s)
Carlos, M
•
•
Milone, A P
•
Dondoglio, E
•
Jang, S
•
Legnardi, M V
•
Mohandasan, A
•
Cordoni, G
•
Lagioia, E P
•
Amarsi, A M
•
Jerjen, H
Abstract
Pseudo two-colour diagrams or Chromosome maps (ChM) indicate that NGC 2808
host five different stellar populations. The existing ChMs have been derived by
the Hubble Space Telescope photometry, and comprise of stars in a small field
of view around the cluster centre. To overcome these limitations, we built a
ChM with U,B,I photometry from ground-based facilities that disentangle the
multiple stellar populations of NGC 2808 over a wider field of view. We used
spectra collected by GIRAFFE@VLT in a sample of 70 red giant branch (RGB) and
seven asymptotic giant branch (AGB) stars to infer the abundances of C, N, O,
Al, Fe, and Ni, which combined with literature data for other elements (Li, Na,
Mg, Si, Ca, Sc, Ti, Cr and Mn), and together with both the classical and the
new ground-based ChMs, provide the most complete chemical characterisation of
the stellar populations in NGC 2808 available to date. As typical of the
multiple population phenomenon in globular clusters, the light elements vary
from one stellar population to another; whereas the iron peak elements show
negligible variation between the different populations (at a level of
$\lesssim0.10$~dex). Our AGB stars are also characterised by the chemical
variations associated with the presence of multiple populations, confirming
that this phase of stellar evolution is affected by the phenomenon as well.
Intriguingly, we detected one extreme O-poor AGB star (consistent with a high
He abundance), challenging stellar evolution models which suggest that highly
He-enriched stars should avoid the AGB phase and evolve as AGB-manqu\'e star.
Volume
519
Issue
2
Start page
1695
Issn Identifier
0035-8711
Rights
open.access
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