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.

Milone, A.p., Marino, A.f., Bedin, L., Piotto, G., Cassisi, S., Dieball, A., et al. (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 [10.1093/mnras/stu030].

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

BUONANNO, ROBERTO
2014-01-01

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.
2014
Pubblicato
Rilevanza internazionale
Articolo
Esperti anonimi
Settore FIS/05 - ASTRONOMIA E ASTROFISICA
English
Con Impact Factor ISI
Milone, A.p., Marino, A.f., Bedin, L., Piotto, G., Cassisi, S., Dieball, A., et al. (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 [10.1093/mnras/stu030].
Milone, Ap; Marino, Af; Bedin, L; 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, R; Null, B; Buonanno, R
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2108/88632
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