Integrated Photometry of Multiple Stellar Populations in Globular Clusters

Journal
Date Issued
2021
Author(s)
Jang, S.
•
Milone, A. P.
•
Lagioia, E. P.
•
Tailo, M.
•
Dondoglio, E.
•
Martorano, M.
•
Mohandasan, A.
•
•
Cordoni, G.
•
Lee, Y. -W.
•
Carlos, M
DOI
Abstract
Evidence that multiple populations (MPs) are common properties of globular clusters (GCs) has accumulated over the past decades from clusters in the Milky Way and in its satellites. This finding has revived research into GCs, and suggested that their formation at high redshift must have been a much more complex phenomenon than imagined before. However, most information on MPs is limited to nearby GCs. The main limitation is that most studies of MPs rely on resolved stars, posing a major challenge to the investigation of the MP phenomenon in distant galaxies. Here we search for integrated colors of old GCs that are sensitive to the MP phenomenon. To do this, we exploit integrated magnitudes of simulated GCs with MPs, and multiband Hubble Space Telescope photometry of 56 Galactic GCs, where MPs are widely studied, and characterized as part of the UV Legacy Survey of Galactic GCs. We find that both integrated CF275W,F336W,F438W and mF275W - mF814W colors strongly correlate with the iron abundance of the host GC. To second order, the pseudo two-color diagram built with these integrated colors is sensitive to the MP phenomenon. In particular, once the dependence on cluster metallicity is removed, the color residuals depend on the maximum internal helium variation within GCs and on the fraction of second-generation stars. This diagram, which we define here for Galactic GCs, has the potential to detect and characterize MPs from integrated photometry of old GCs, thus providing the possibility to extend their investigation outside the Local Group.
Volume
920
Issue
2
Start page
129
Uri
Url
Issn Identifier
0004-637X
Ads BibCode
2021ApJ...920..129J
Rights
open.access
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