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The M 4 Core Project with HST - II. Multiple stellar populations at the bottom of the main sequence

The M 4 Core Project with HST - II. Multiple stellar populations at the bottom of the main sequence
The M 4 Core Project with HST - II. Multiple stellar populations at the bottom of the main sequence
The M 4 Core Project with HST is designed to exploit the Hubble Space Telescope (HST) to investigate the central regions of M 4, the Globular Cluster closest to the Sun. In this paper we combine optical and near-infrared photometry to study multiple stellar populations in M 4. We detected two sequences of M-dwarfs containing ˜38 per cent (MSI) and ˜62 per cent (MSII) of MS stars below the main-sequence (MS) knee. We compare our observations with those of NGC 2808, which is the only other GCs where multiple MSs of very low-mass stars have been studied to date. We calculate synthetic spectra for M-dwarfs, assuming the chemical composition mixture inferred from spectroscopic studies of stellar populations along the red giant branch, and different helium abundances, and we compare predicted and observed colours. Observations are consistent with two populations, one with primordial abundance and another with enhanced nitrogen and depleted oxygen.
stars: Population II, globular clusters: individual: NGC 6121
1365-2966
1588-1595
Milone, A.P.
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Marino, A.F.
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Bedin, L.R.
e5bc5fc4-4bb0-4889-8a8e-f800eee960bd
Piotto, G.
d697145a-540d-43cd-8807-e87acc24ed8d
Cassisi, S.
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Dieball, A.
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Anderson, J.
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Jerjen, H.
a3f9dacf-b268-4b6f-8c9a-a31eeda50ce6
Asplund, M.
0e18a525-7395-4288-8884-8dd57d7b7457
Bellini, A.
ba36df58-2ce5-4eee-b913-c03799f84dc7
Brogaard, K.
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Dotter, A.
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Giersz, M.
e4577428-513f-4d9a-a3e1-0e773b8ad837
Heggie, D.C.
ef04ac6c-58a1-4e1c-a95a-6118d3954812
Knigge, C.
ac320eec-631a-426e-b2db-717c8bf7857e
Rich, R.M.
ef2a92bd-15a6-4203-8d1b-fb7b368fe385
van den Berg, M.
a26a14f7-7078-4654-932f-0a31c2629263
Buonanno, R.
5ccd1dfd-2547-4a95-b7ef-4ebdc1cab43e
Milone, A.P.
31980f73-0de9-4d40-8544-f89b70b2a2f0
Marino, A.F.
b0c08fdc-c646-4e78-8c42-19380badc141
Bedin, L.R.
e5bc5fc4-4bb0-4889-8a8e-f800eee960bd
Piotto, G.
d697145a-540d-43cd-8807-e87acc24ed8d
Cassisi, S.
3e272f78-bab2-4f80-be17-c79d5f230170
Dieball, A.
5f595453-aa6b-4067-a3e1-026867fb9f7a
Anderson, J.
717a1450-3122-4f61-8e1c-5a1fbc781712
Jerjen, H.
a3f9dacf-b268-4b6f-8c9a-a31eeda50ce6
Asplund, M.
0e18a525-7395-4288-8884-8dd57d7b7457
Bellini, A.
ba36df58-2ce5-4eee-b913-c03799f84dc7
Brogaard, K.
41cfca92-7dbf-421a-9198-9358ef3d1c67
Dotter, A.
1c1815ba-06ff-4255-8f8f-cef5325e7523
Giersz, M.
e4577428-513f-4d9a-a3e1-0e773b8ad837
Heggie, D.C.
ef04ac6c-58a1-4e1c-a95a-6118d3954812
Knigge, C.
ac320eec-631a-426e-b2db-717c8bf7857e
Rich, R.M.
ef2a92bd-15a6-4203-8d1b-fb7b368fe385
van den Berg, M.
a26a14f7-7078-4654-932f-0a31c2629263
Buonanno, R.
5ccd1dfd-2547-4a95-b7ef-4ebdc1cab43e

Milone, A.P., Marino, A.F., Bedin, L.R., Piotto, G., Cassisi, S., Dieball, A., Anderson, J., Jerjen, H., Asplund, M., Bellini, A., Brogaard, K., Dotter, A., Giersz, M., Heggie, D.C., Knigge, C., Rich, R.M., van den Berg, M. and Buonanno, R. (2014) The M 4 Core Project with HST - II. Multiple stellar populations at the bottom of the main sequence. Monthly Notices of the Royal Astronomical Society, 439 (2), 1588-1595. (doi:10.1093/mnras/stu030).

Record type: Article

Abstract

The M 4 Core Project with HST is designed to exploit the Hubble Space Telescope (HST) to investigate the central regions of M 4, the Globular Cluster closest to the Sun. In this paper we combine optical and near-infrared photometry to study multiple stellar populations in M 4. We detected two sequences of M-dwarfs containing ˜38 per cent (MSI) and ˜62 per cent (MSII) of MS stars below the main-sequence (MS) knee. We compare our observations with those of NGC 2808, which is the only other GCs where multiple MSs of very low-mass stars have been studied to date. We calculate synthetic spectra for M-dwarfs, assuming the chemical composition mixture inferred from spectroscopic studies of stellar populations along the red giant branch, and different helium abundances, and we compare predicted and observed colours. Observations are consistent with two populations, one with primordial abundance and another with enhanced nitrogen and depleted oxygen.

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More information

Published date: 1 April 2014
Keywords: stars: Population II, globular clusters: individual: NGC 6121

Identifiers

Local EPrints ID: 430095
URI: http://eprints.soton.ac.uk/id/eprint/430095
ISSN: 1365-2966
PURE UUID: c1922390-ca92-493d-8d98-e56dfe0a4802

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Date deposited: 11 Apr 2019 16:30
Last modified: 16 Mar 2024 00:53

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Contributors

Author: A.P. Milone
Author: A.F. Marino
Author: L.R. Bedin
Author: G. Piotto
Author: S. Cassisi
Author: A. Dieball
Author: J. Anderson
Author: H. Jerjen
Author: M. Asplund
Author: A. Bellini
Author: K. Brogaard
Author: A. Dotter
Author: M. Giersz
Author: D.C. Heggie
Author: C. Knigge
Author: R.M. Rich
Author: M. van den Berg
Author: R. Buonanno

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