Disappearance of the extended main sequence turn-off in intermediate age clusters as a consequence of magnetic braking

Abstract

Extended MS turn-offs are features commonly found in the colour-magnitude diagrams of young and intermediate age (less than about 2 Gyr) massive star clusters, where the MS turn-off is broader than can be explained by photometric uncertainties, crowding, or binarity. Rotation is suspected to be the cause of this feature, by accumulating fast rotating stars, strongly affected by gravity darkening and rotation-induced mixing, near the MS turn-off. This scenario successfully reproduces the tight relation between the age and the actual extent in luminosity of the extended MS turn-off of observed clusters. Below a given mass (dependent on the metallicity), stars are efficiently braked early on the MS due to the interaction of stellar winds and the surface magnetic field, making their tracks converge towards those of non-rotating tracks in the HRD. When these stars are located at the turn-off of a cluster, their slow rotation causes the extended MS turn-off feature to disappear. We investigate the maximal mass for which this braking occurs at different metallicities, and determine the age above which no extended MS turn-off is expected in clusters. Our models predict that the extended MS turn-off phenomenon disappears at ages older than about 2 Gyr. There is a trend with the metallicity, the age at which the disappearance occurs becoming older at higher metallicity. These results are robust between the two codes used in this work, despite some differences in the input physics and in particular in the detailed description of rotation-induced internal processes and of angular momentum extraction by stellar winds. Comparing our results with clusters in the LMC and Galaxy shows a very good fit to the observations. This strengthens the rotation scenario to explain the cause of the extended MS turn-off phenomenon.

arXiv comment7 pages, 4 figures, accepted for publication in A&A

References in corpus (38)

• Grids of stellar models with rotation - I. Models from 0.8 to 120 Msun at solar metallicity (Z = 0.014)
• Rotating Massive Main-Sequence Stars I: Grids of Evolutionary Models and Isochrones
• The evolution of rotating stars
• Presupernova Evolution of Rotating Massive Stars II: -- Evolution of the Surface Properties
• Grids of stellar models with rotation - III. Models from 0.8 to 120 Msun at a metallicity Z = 0.002
• The Mass-Dependence of Angular Momentum Evolution in Sun-Like Stars
• Thermohaline instability and rotation-induced mixing. III - Grid of stellar models and asymptotic asteroseismic quantities from the pre-main sequence up to the AGB for low- and intermediate-mass stars at various metallicities
• Gravity darkening in rotating stars
• The Effect of Stellar Rotation on Colour-Magnitude Diagrams: On the apparent presence of multiple populations in intermediate age stellar clusters
• A double main sequence turn-off in the rich star cluster NGC 1846 in the Large Magellanic Cloud
• Extended Main Sequence Turnoffs in Intermediate-Age Star Clusters: A Correlation Between Turnoff Width and Early Escape Velocity
• Rotating models of young solar-type stars : Exploring braking laws and angular momentum transport processes
• Diagnoses to unravel secular hydrodynamical processes in rotating main sequence stars
• Multiple stellar populations in Magellanic Cloud clusters. VI. A survey of multiple sequences and Be stars in young clusters
• Populations of rotating stars III. SYCLIST, the new Geneva Population Synthesis code
• Extended main sequence turnoff as a common feature of Milky Way open clusters
• Apparent Age Spreads in Clusters and the Role of Stellar Rotation
• Multiple stellar populations in Magellanic Cloud clusters. III. The first evidence of an extended main sequence turn-off in a young cluster: NGC1856
• Extended Main Sequence Turnoffs in Open Clusters as Seen by Gaia: I. NGC 2818 and the Role of Stellar Rotation
• Rotating Stellar Models Can Account for the Extended Main Sequence Turnoffs in Intermediate Age Clusters
• NGC 1866: First Spectroscopic Detection of Fast Rotating Stars in a Young LMC Cluster
• Can rotation explain the multiple main sequence turn-offs of Magellanic Cloud star clusters?
• Different stellar rotation in the two main sequences of the young globular cluster NGC1818: first direct spectroscopic evidence
• No Evidence for Significant Age Spreads in Young Massive LMC Clusters
• The effects of rotation on the main-sequence turnoff of intermediate-age massive star clusters
• Multiple stellar populations in Magellanic Cloud clusters. V. The split main sequence of the young cluster NGC1866
• Effects of rotational mixing on the asteroseismic properties of solar-type stars
• Cluster kinematics and stellar rotation in NGC 419 with MUSE and adaptive optics
• Anisotropic turbulent transport in stably stratified rotating stellar radiation zones
• Angular Momentum Transport by Internal Gravity Waves II- Pop II stars from the Li plateau to the horizontal branch
• A Young Cluster With an Extended Main Sequence Turnoff: Confirmation of a Prediction of the Stellar Rotation Scenario
• Extended Main Sequence Turnoffs in Intermediate-Age Star Clusters: Stellar Rotation diminishes, but does not eliminate, Age Spreads
• The magnetic strip(s) in the advanced phases of stellar evolution - Theoretical convective turnover timescale and Rossby number for low- and intermediate-mass stars up to the AGB at various metallicities
• New Clues to the Cause of Extended Main Sequence Turn-Offs in Intermediate-Age Star Clusters in the Magellanic Clouds
• On the Interpretation of Sub-Giant Branch Morphologies of Intermediate-Age Star Clusters with Extended Main Sequence Turnoffs
• The Minimum Mass of Rotating Main Sequence Stars and its Impact on the Nature of Extended Main Sequence Turnoffs in Intermediate-Age Star Clusters in the Magellanic Clouds
• Influence of Rotation on Stellar Evolution
• The effects of the overshooting of the convective core on main-sequence turnoffs of young- and intermediate-age star clusters

Cited by in corpus (24)

• Probing the interior physics of stars through asteroseismology
• How stellar rotation shapes the colour magnitude diagram of the massive intermediate-age star cluster NGC 1846
• Combined Effects of Rotation and Age Spreads on Extended Main Sequence Turn Offs
• Stellar rotation and the extended main sequence turnoff in the open cluster NGC 5822
• On the Origin of the Bimodal Rotational Velocity Distribution in Stellar Clusters: Rotation on the Pre-Main Sequence
• MESA models with magnetic braking
• Isochrone-cloud fitting of the extended Main-Sequence Turn-Off of young clusters
• The Swift/UVOT Stars Survey. III. Photometry and Color-Magnitude Diagrams of 103 Galactic Open Clusters
• NGC1818 unveils the origin of the extended main-sequence turn-off in young Magellanic Clouds clusters
• On the origin of UV-dim stars: a population of rapidly rotating shell stars?
• Hubble Space Telescope survey of Magellanic Cloud star clusters. UV-dim stars in young clusters
• The extended Main-Sequence Turnoff of the Milky Way open cluster Collinder 347
• Searching for globular cluster chemical anomalies on the main sequence of a young massive cluster
• The Gaia-ESO survey: A spectroscopic study of the young open cluster NGC 3293
• On aging star clusters using red supergiants independent of the fraction of interacting binary stars
• Hubble Space Telescope survey of Magellanic Cloud star clusters. Binaries among the split main sequences of NGC 1818, NGC 1850, and NGC 2164
• When does the onset of multiple stellar populations in star clusters occur-II: No evidence of multiple stellar populations in Lindsay 113
• The spatial distributions of blue main-sequence stars in Magellanic Cloud star clusters
• The wide upper main sequence and main sequence turnoff of the ~ 800 Myr old star cluster NGC1831
• Signature of a chemical spread in the open cluster M37
• At what mass are stars braked? The implication from the turnoff morphology of NGC 6819
• The VISCACHA Survey: XIII. The extended main-sequence turn-off in intermediate-age low-mass clusters
• The impact of stellar rotations and binaries on the shape of upper main sequence near turn off in open cluster NGC\,6067
• One size does not fit all: Evidence for a range of mixing efficiencies in stellar evolution calculations