A discovery of young stellar objects in older clusters of the Large Magellanic Cloud

Abstract

Recent studies have shown that an extended main-sequence turn-off is a common feature among intermediate-age clusters (1--3 Gyr) in the Magellanic Clouds. Multiple-generation star formation and stellar rotation or interacting binaries have been proposed to explain the feature. However, it remains controversial in the field of stellar populations. Here we present the main results of an ongoing star formation among older star clusters in the Large Magellanic Cloud. Cross-matching the positions of star clusters and young stellar objects has yielded 15 matches with 7 located in the cluster center. We demonstrate that this is not by chance by estimating local number densities of young stellar objects for each star cluster. This method is not based on isochrone fitting, which leads to some uncertainties in age estimation and methods of background subtraction. We also find no direct correlation between atomic hydrogen and the clusters. This suggests that gas accretion for fueling the star formation must be happening in situ. These findings support for the multiple-generations scenario as a plausible explanation for the extended main-sequence turn-off.

arXiv comment6 pages, 4 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society Letters. Media release: http://www.icrar.org/starclusters/

References in corpus (35)

• Spitzer Survey of the Large Magellanic Cloud, Surveying the Agents of a Galaxy's Evolution (SAGE) I: Overview and Initial Results
• A Triple Main Sequence in the Globular Cluster NGC 2808
• Formation and Dynamical Evolution of Multiple Stellar Generations in Globular Clusters
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. I. Overview of the Project and Detection of Multiple Stellar Populations
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. IX. The Atlas of Multiple Stellar Populations
• The Magellanic Clouds Photometric Survey: The Large Magellanic Cloud Stellar Catalog and Extinction Map
• The Magellanic Clouds Photometric Survey: The Small Magellanic Cloud Stellar Catalog and Extinction Map
• Young Stellar Objects in the Gould Belt
• 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
• A general catalogue of extended objects in the Magellanic System
• Multiple stellar populations in three rich Large Magellanic Cloud star clusters
• Ages and Luminosities of Young SMC/LMC Star Clusters and the recent Star Formation History of the Clouds
• Multiple stellar populations in Magellanic Clouds clusters. I. An ordinary feature for intermediate age globulars in the LMC?
• High and Intermediate-Mass Young Stellar Objects in the Large Magellanic Cloud
• Secondary star formation within massive star clusters: Origin of multiple stellar populations in globular clusters
• Extended Main Sequence Turnoffs in Intermediate-Age Star Clusters: A Correlation Between Turnoff Width and Early Escape Velocity
• Constraining Globular Cluster Formation Through Studies of Young Massive Clusters: I. A lack of ongoing star formation within young clusters
• Recurrent gas accretion by massive star clusters, multiple stellar populations and mass thresholds for spherical stellar systems
• Population Parameters of Intermediate-Age Star Clusters in the Large Magellanic Cloud. I. NGC 1846 and its Wide Main Sequence Turnoff
• Multiple stellar populations in Magellanic Cloud clusters. III. The first evidence of an extended main sequence turn-off in a young cluster: NGC1856
• The extended Main Sequence Turn Off cluster NGC1856: rotational evolution in a coeval stellar ensemble
• A statistical study of binary and multiple clusters in the LMC
• The effects of rotation on the main-sequence turnoff of intermediate-age massive star clusters
• The exclusion of a significant range of ages in a massive star cluster
• On the origin of double main-sequence turn-offs in star clusters of the Magellanic Clouds
• Photometric determination of the mass accretion rate of pre-main sequence stars. IV. Recent star formation in NGC 602
• The youngest massive protostars in the Large Magellanic Cloud
• Multiple stellar populations in Magellanic Cloud clusters. II. Evidence also in the young NGC1844?
• Formation of new stellar populations from gas accreted by massive young star clusters
• On the Interpretation of Sub-Giant Branch Morphologies of Intermediate-Age Star Clusters with Extended Main Sequence Turnoffs
• New Constraints on the Star Formation History of the Star Cluster NGC 1856
• The clustered nature of star formation. Pre--main-sequence clusters in the star-forming region NGC 602/N90 in the Small Magellanic Cloud
• The VMC Survey - XII. Star cluster candidates in the Large Magellanic Cloud
• No evidence for younger stellar generations within the intermediate age massive clusters NGC 1783, NGC 1696 and NGC 411

Cited by in corpus (9)

• NGC 1866: First Spectroscopic Detection of Fast Rotating Stars in a Young LMC Cluster
• Evidence for feedback and stellar-dynamically regulated bursty star cluster formation: the case of the Orion Nebula Cluster
• Extended Main Sequence Turnoffs in Intermediate-Age Star Clusters: Stellar Rotation diminishes, but does not eliminate, Age Spreads
• The origin of discrete multiple stellar populations in globular clusters
• The dynamical origin of multiple populations in intermediate-age clusters in the Magellanic Clouds
• Globular cluster formation with multiple stellar populations: self-enrichment in fractal massive molecular clouds
• Formation of globular clusters with multiple stellar populations from massive gas clumps in high-z gas-rich dwarf galaxies
• Star formation within globular clusters:discrete multiple bursts and top-light mass functions
• When does the onset of multiple stellar populations in star clusters occur-II: No evidence of multiple stellar populations in Lindsay 113