Chromosome maps of globular clusters from wide-field ground-based photometry
Date Issued
2022
Author(s)
Jang, S
•
Milone, A. P.
•
Legnardi, M V
•
•
Mastrobuono-Battisti, A
•
Dondoglio, E
•
Lagioia, E P
•
Casagrande, L
•
Carlos, M
•
Mohandasan, A
•
Cordoni, G
•
Bortolan, E
•
Lee, Y-W
Abstract
Hubble Space Telescope (HST) photometry is providing an extensive analysis of
globular clusters (GCs). In particular, the pseudo two-colour diagram dubbed
'chromosome map (ChM)' allowed to detect and characterize their multiple
populations with unprecedented detail. The main limitation of these studies is
the small field of view of HST, which makes it challenging to investigate some
important aspects of the multiple populations, such as their spatial
distributions and the internal kinematics in the outermost cluster regions. To
overcome this limitation, we analyse state-of-art wide-field photometry of 43
GCs obtained from ground-based facilities. We derived high-resolution reddening
maps and corrected the photometry for differential reddening when needed. We
use photometry in the U, B, and I bands to introduce the $\Delta c_{\rm U,B,I}$
vs. $\Delta_{\rm B,I}$ ChM of red-giant branch (RGB) and asymptotic-giant
branch (AGB) stars. We demonstrate that this ChM, which is built with wide-band
ground-based photometry, is an efficient tool to identify first- and
second-generation stars (1G and 2G) over a wide field of view. To illustrate
its potential, we derive the radial distribution of multiple populations in NGC
288 and infer their chemical composition. We present the ChMs of RGB stars in
29 GCs and detect a significant degree of variety. The fraction of 1G and 2G
stars, the number of subpopulations, and the extension of the ChMs
significantly change from one cluster to another. Moreover, the metal-poor and
metal-rich stars of Type II GCs define distinct sequences in the ChM. We
confirm the presence of extended 1G sequences.
Volume
517
Issue
4
Start page
5687
Issn Identifier
0035-8711
Rights
open.access