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

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

doi:10.1093/mnras/stu030

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

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

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

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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 M4.We detected two sequences of M-dwarfs containing ~38 per cent (MSI) and ~62 per cent (MS_II) 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.

Original language	English
Pages (from-to)	1588-1595
Number of pages	8
Journal	Monthly Notices of the Royal Astronomical Society
Volume	439
Issue number	2
DOIs	https://doi.org/10.1093/mnras/stu030
Publication status	Published - Apr 2014

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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., & 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. https://doi.org/10.1093/mnras/stu030

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

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 M4.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.",

keywords = "Globular clusters: individual: NGC 6121, Stars: Population II",

author = "Milone, {A. P.} and Marino, {A. F.} and Bedin, {L. R.} and G. Piotto and S. Cassisi and A. Dieball and J. Anderson and H. Jerjen and M. Asplund and A. Bellini and K. Brogaard and A. Dotter and M. Giersz and Heggie, {D. C.} and C. Knigge and Rich, {R. M.} and {van den Berg}, M. and R. Buonanno",

year = "2014",

month = apr,

doi = "10.1093/mnras/stu030",

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Milone, AP, Marino, AF, Bedin, LR, Piotto, G, Cassisi, S, Dieball, A, Anderson, J, Jerjen, H, Asplund, M, Bellini, A, Brogaard, K, Dotter, A, Giersz, M, Heggie, DC, Knigge, C, Rich, RM, van den Berg, M & 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, vol. 439, no. 2, pp. 1588-1595. https://doi.org/10.1093/mnras/stu030

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T1 - The M 4 Core Project with HST-II. Multiple stellar populations at the bottom of the main sequence

AU - Milone, A. P.

AU - Marino, A. F.

AU - Bedin, L. R.

AU - Piotto, G.

AU - Cassisi, S.

AU - Dieball, A.

AU - Anderson, J.

AU - Jerjen, H.

AU - Asplund, M.

AU - Bellini, A.

AU - Brogaard, K.

AU - Dotter, A.

AU - Giersz, M.

AU - Heggie, D. C.

AU - Knigge, C.

AU - Rich, R. M.

AU - van den Berg, M.

AU - Buonanno, R.

PY - 2014/4

Y1 - 2014/4

N2 - 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 M4.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.

AB - 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 M4.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.

KW - Globular clusters: individual: NGC 6121

KW - Stars: Population II

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U2 - 10.1093/mnras/stu030

DO - 10.1093/mnras/stu030

M3 - Article

SN - 0035-8711

VL - 439

SP - 1588

EP - 1595

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

IS - 2

ER -

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

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