The two metallicity groups of the globular cluster M 22: A chemical perspective

A. F. Marino; C. Sneden; R. P. Kraft; G. Wallerstein; J. E. Norris; G. Da Costa; A. P. Milone; I. I. Ivans; G. Gonzalez; J. P. Fulbright; M. Hilker; G. Piotto; M. Zoccali; P. B. Stetson

doi:10.1051/0004-6361/201116546

The two metallicity groups of the globular cluster M 22: A chemical perspective

A. F. Marino^*, C. Sneden, R. P. Kraft, G. Wallerstein, J. E. Norris, G. Da Costa, A. P. Milone, I. I. Ivans, G. Gonzalez, J. P. Fulbright, M. Hilker, G. Piotto, M. Zoccali, P. B. Stetson

^*Corresponding author for this work

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Abstract

We present a detailed chemical composition analysis of 35 red giant stars in the globular cluster M 22. High resolution spectra for this study were obtained at five observatories, and analyzed in a uniform manner. We have determined abundances of representative light proton-capture, α, Fe-peak and neutron-capture element groups. Our aim is to better understand the peculiar chemical enrichment history of this cluster, in which two stellar groups are characterized by a different content in iron, neutron capture elements Y, Zr and Ba, and α element Ca. The principal results of this study are: (i) substantial star-to-star metallicity scatter (-2.0 [Fe/H]-1.6); (ii) enhancement of s-process/r-process neutron-capture abundance ratios in a fraction of giants, positively correlated with metallicity; (iii) sharp separation between the s-process-rich and s-process-poor groups by [La/Eu] ratio; (iv) possible increase of [Cu/Fe] ratios with increasing [Fe/H], suggesting that this element also has a significant s-process component; and (v)presence of Na-O and C-N anticorrelations in both the stellar groups.

Original language	English
Article number	A8
Journal	Astronomy and Astrophysics
Volume	532
DOIs	https://doi.org/10.1051/0004-6361/201116546
Publication status	Published - 2011

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Marino, A. F., Sneden, C., Kraft, R. P., Wallerstein, G., Norris, J. E., Da Costa, G., Milone, A. P., Ivans, I. I., Gonzalez, G., Fulbright, J. P., Hilker, M., Piotto, G., Zoccali, M., & Stetson, P. B. (2011). The two metallicity groups of the globular cluster M 22: A chemical perspective. Astronomy and Astrophysics, 532, Article A8. https://doi.org/10.1051/0004-6361/201116546

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title = "The two metallicity groups of the globular cluster M 22: A chemical perspective",

abstract = "We present a detailed chemical composition analysis of 35 red giant stars in the globular cluster M 22. High resolution spectra for this study were obtained at five observatories, and analyzed in a uniform manner. We have determined abundances of representative light proton-capture, α, Fe-peak and neutron-capture element groups. Our aim is to better understand the peculiar chemical enrichment history of this cluster, in which two stellar groups are characterized by a different content in iron, neutron capture elements Y, Zr and Ba, and α element Ca. The principal results of this study are: (i) substantial star-to-star metallicity scatter (-2.0 [Fe/H]-1.6); (ii) enhancement of s-process/r-process neutron-capture abundance ratios in a fraction of giants, positively correlated with metallicity; (iii) sharp separation between the s-process-rich and s-process-poor groups by [La/Eu] ratio; (iv) possible increase of [Cu/Fe] ratios with increasing [Fe/H], suggesting that this element also has a significant s-process component; and (v)presence of Na-O and C-N anticorrelations in both the stellar groups.",

keywords = "Globular clusters: individual: M 22 (NGC 6656), Stars: Population II, Stars: abundances, Techniques: spectroscopic",

author = "Marino, {A. F.} and C. Sneden and Kraft, {R. P.} and G. Wallerstein and Norris, {J. E.} and {Da Costa}, G. and Milone, {A. P.} and Ivans, {I. I.} and G. Gonzalez and Fulbright, {J. P.} and M. Hilker and G. Piotto and M. Zoccali and Stetson, {P. B.}",

year = "2011",

doi = "10.1051/0004-6361/201116546",

language = "English",

volume = "532",

journal = "Astronomy and Astrophysics",

issn = "0004-6361",

publisher = "EDP Sciences",

}

TY - JOUR

T1 - The two metallicity groups of the globular cluster M 22

T2 - A chemical perspective

AU - Marino, A. F.

AU - Sneden, C.

AU - Kraft, R. P.

AU - Wallerstein, G.

AU - Norris, J. E.

AU - Da Costa, G.

AU - Milone, A. P.

AU - Ivans, I. I.

AU - Gonzalez, G.

AU - Fulbright, J. P.

AU - Hilker, M.

AU - Piotto, G.

AU - Zoccali, M.

AU - Stetson, P. B.

PY - 2011

Y1 - 2011

N2 - We present a detailed chemical composition analysis of 35 red giant stars in the globular cluster M 22. High resolution spectra for this study were obtained at five observatories, and analyzed in a uniform manner. We have determined abundances of representative light proton-capture, α, Fe-peak and neutron-capture element groups. Our aim is to better understand the peculiar chemical enrichment history of this cluster, in which two stellar groups are characterized by a different content in iron, neutron capture elements Y, Zr and Ba, and α element Ca. The principal results of this study are: (i) substantial star-to-star metallicity scatter (-2.0 [Fe/H]-1.6); (ii) enhancement of s-process/r-process neutron-capture abundance ratios in a fraction of giants, positively correlated with metallicity; (iii) sharp separation between the s-process-rich and s-process-poor groups by [La/Eu] ratio; (iv) possible increase of [Cu/Fe] ratios with increasing [Fe/H], suggesting that this element also has a significant s-process component; and (v)presence of Na-O and C-N anticorrelations in both the stellar groups.

AB - We present a detailed chemical composition analysis of 35 red giant stars in the globular cluster M 22. High resolution spectra for this study were obtained at five observatories, and analyzed in a uniform manner. We have determined abundances of representative light proton-capture, α, Fe-peak and neutron-capture element groups. Our aim is to better understand the peculiar chemical enrichment history of this cluster, in which two stellar groups are characterized by a different content in iron, neutron capture elements Y, Zr and Ba, and α element Ca. The principal results of this study are: (i) substantial star-to-star metallicity scatter (-2.0 [Fe/H]-1.6); (ii) enhancement of s-process/r-process neutron-capture abundance ratios in a fraction of giants, positively correlated with metallicity; (iii) sharp separation between the s-process-rich and s-process-poor groups by [La/Eu] ratio; (iv) possible increase of [Cu/Fe] ratios with increasing [Fe/H], suggesting that this element also has a significant s-process component; and (v)presence of Na-O and C-N anticorrelations in both the stellar groups.

KW - Globular clusters: individual: M 22 (NGC 6656)

KW - Stars: Population II

KW - Stars: abundances

KW - Techniques: spectroscopic

UR - http://www.scopus.com/inward/record.url?scp=79960237297&partnerID=8YFLogxK

U2 - 10.1051/0004-6361/201116546

DO - 10.1051/0004-6361/201116546

M3 - Article

SN - 0004-6361

VL - 532

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

M1 - A8

ER -

The two metallicity groups of the globular cluster M 22: A chemical perspective

Abstract

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