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|Title:||The M 4 Core Project with HST - II. Multiple stellar populations at the bottom of the main sequence||Authors:||Milone, A. P.
Marino, A. F.
Bedin, L. R.
Heggie, D. C.
Rich, R. M.
van den Berg, M.
|Issue Date:||2014||Journal:||MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY||Number:||439||Issue:||2||First Page:||1588||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 (MS<SUB>I</SUB>) and ̃62 per cent (MS<SUB>II</SUB>) 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.||Description:||APM and HJ acknowledge the financial support from the Australian Research Council through Discovery Project grant DP120100475. SC is grateful for financial support from PRIN-INAF 2011 ‘Multiple Populations in Globular Clusters: their role in the Galaxy assembly’ (PI: E. Carretta), and from PRIN MIUR 2010-2011, project ‘The Chemical and Dynamical Evolution of the Milky Way and Local Group Galaxies’, prot. 2010LY5N2T (PI: F. Matteucci). LRB and GP acknowledge PRIN-INAF 2012 funding under the project entitled: ‘The M4 Core Project with Hubble Space Telescope’.||URI:||http://hdl.handle.net/20.500.12386/12657||ISSN:||0035-8711||DOI:||10.1093/mnras/stu030||Bibcode ADS:||2014MNRAS.439.1588M|
|Appears in Collections:||1.01 Articoli in rivista|
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