Bibcode
Mészáros, Sz.; García-Hernández, D. A.; Cassisi, Santi; Monelli, M.; Szigeti, László; Dell'Agli, F.; Derekas, Alíz; Masseron, T.; Shetrone, Matthew; Stetson, Peter; Zamora, O.
Bibliographical reference
Monthly Notices of the Royal Astronomical Society, Volume 475, Issue 2, p.1633-1645
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4
2018
Citations
6
Refereed citations
6
Description
In this paper, we describe the photometric and spectroscopic properties
of multiple populations in seven northern globular clusters. In this
study, we employ precise ground-based photometry from the private
collection of Stetson, space photometry from the Hubble Space Telescope
(HST), literature abundances of Na and O, and Apache Point Observatory
Galactic Evolution Experiment (APOGEE) survey abundances for Mg, Al, C,
and N. Multiple populations are identified by their position in the
CU, B, I -Vpseudo colour-magnitude diagram (pseudo-CMD) and
confirmed with their chemical composition determined using abundances.
We confirm the expectation from previous studies that the red giant
branches (RGBs) in all seven clusters are split and the different
branches have different chemical compositions. The Mg-Al
anticorrelations were well explored by the APOGEE and Gaia-ESO surveys
for most globular clusters, some clusters showing bimodal distributions,
while others continuous distributions. Even though the structure (i.e.
bimodal versus continuous) of Mg-Al can greatly vary, the Al-rich and
Al-poor populations do not seem to have very different photometric
properties, agreeing with theoretical calculations. There is no
one-to-one correspondence between the Mg-Al anticorrelation shape
(bimodal versus continuous) and the structure of the RGB seen in the HST
pseudo-CMDs, with the HST photometric information usually implying more
complex formation/evolution histories than the spectroscopic ones. We
report on finding two second-generation horizontal branch (HB) stars in
M5, and five second-generation asymptotic giant branch (AGB) stars in
M92, which is the most metal-poor cluster to date in which
second-generation AGB stars have been observed.
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