C.D.S. - SIMBAD4 rel 1.7 - 2020.08.03CEST23:53:39

2018A&A...616A.168L - Astronomy and Astrophysics, volume 616A, 168-168 (2018/8-1)

Chemical inhomogeneities amongst first population stars in globular clusters. Evidence for He variations.


Abstract (from CDS):

Spreads in light element abundances among stars (also known as multiple populations) are observed in nearly all globular clusters. One way to map such chemical variations using high-precision photometry is to employ a suitable combination of stellar magnitudes in the F275W, F336W, F438W, and F814W filters (called the "chromosome map"), to maximise the separation between the different multiple populations. For each individual cluster its chromosome map separates the first population (with metal abundance patterns typical of field halo stars) from the second population (which displays distinctive abundance variations among a specific group of light elements). Surprisingly, the distribution of first population stars in chromosome maps of several but not all clusters has been found to be more extended than expected from purely observational errors, suggesting a chemically inhomogeneous origin. We consider here three clusters with similar metallicity ([Fe/H]~-1.3) and different chromosome maps, namely NGC 288, M 3, and NGC 2808, and argue that the first population extended distribution (as observed in two of these clusters) is due to spreads of the initial helium abundance and possibly a small range of nitrogen abundances as well. The presence of a range of initial He and N abundances amongst stars traditionally thought to have homogeneous composition, and that these spreads appear only in some clusters, challenges the scenarios put forward so far to explain the multiple population phenomenon.

Abstract Copyright: © ESO 2018

Journal keyword(s): stars: abundances - stars: atmospheres - Hertzsprung - Russell and C-M diagrams - globular clusters: general - galaxies: groups: individual: (NGC 288, M 3, NGC 2808)

Simbad objects: 4

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Number of rows : 4

N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
1 NGC 288 GlC 00 52 45.24 -26 34 57.4   10 8.13     ~ 923 0
2 IRAS 09110-6439 GlC 09 12 03.10 -64 51 48.6   7.77 5.69     ~ 1248 0
3 M 3 GlC 13 42 11.62 +28 22 38.2     6.39     ~ 2269 0
4 M 4 GlC 16 23 35.22 -26 31 32.7           ~ 1678 0

    Equat.    Gal    SGal    Ecl

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