The clustered nature of star formation. Pre--main-sequence clusters in the star-forming region NGC 602/N90 in the Small Magellanic Cloud

Abstract

Located at the tip of the wing of the Small Magellanic Cloud (SMC), the star-forming region NGC602/N90 is characterized by the HII nebular ring N90 and the young cluster of pre--main-sequence (PMS) and early-type main sequence stars NGC602. We present a thorough cluster analysis of the stellar sample identified with HST/ACS camera in the region. We show that apart from the central cluster, low-mass PMS stars are congregated in thirteen additional small compact sub-clusters at the periphery of NGC602. We find that the spatial distribution of the PMS stars is bimodal, with an unusually large fraction (~60%) of the total population being clustered, while the remaining is diffusely distributed in the inter-cluster area. From the corresponding color-magnitude diagrams we disentangle an age-difference of ~2.5Myr between NGC602 and the compact sub-clusters which appear younger. The diffuse PMS population appears to host stars as old as those in NGC602. Almost all detected PMS sub-clusters appear to be centrally concentrated. When the complete PMS stellar sample, including both clustered and diffused stars, is considered in our cluster analysis, it appears as a single centrally concentrated stellar agglomeration, covering the whole central area of the region. Considering also the hot massive stars of the system, we find evidence that this agglomeration is hierarchically structured. Based on our findings we propose a scenario, according to which the region NGC602/N90 experiences an active clustered star formation for the last ~5Myr. The central cluster NGC602 was formed first and rapidly started dissolving into its immediate ambient environment, possibly ejecting also massive stars found away from its center. Star formation continued in sub-clusters of a larger stellar agglomeration, introducing an age-spread of the order of 2.5Myr among the PMS populations.

Accepted for publication by The Astrophysical Journal. 14 pages, 11 figures, 1 table, 2-columns format

References in corpus (8)

• Theory of Star Formation
• The Pisa pre-main sequence tracks and isochrones. A database covering a wide range of Z, Y, mass, and age values
• Dense Stellar Populations: Initial Conditions
• Identifying star clusters in a field: A comparison of different algorithms
• Testing pre-main sequence models: the power of a Bayesian approach
• NGC 346 in The Small Magellanic Cloud. IV. Triggered Star Formation in the HII Region N66
• A Panchromatic View OF NGC 602: Time-Resolved Star Formation with the Hubble and Spitzer Space Telescopes
• Pre--Main-Sequence stellar populations across Shapley Constellation III. I. Photometric Analysis and Identification

Cited by in corpus (24)

• On the (non-)enhancement of the Lyman α equivalent width by a multiphase interstellar medium
• Metallicity Fluctuation Statistics in the Interstellar Medium and Young Stars. I. Variance and Correlation
• Structure and mass segregation in Galactic stellar clusters
• Hubble Tarantula Treasury Project: Unraveling Tarantula's Web. I. Observational overview and first results
• Star formation activity and the spatial distribution and mass segregation of dense cores in the early phases of star formation
• The Onset of Massive Star Formation: The Evolution of Temperature and Density Structure in an Infrared Dark Cloud
• Stellar clusterings around "Isolated" Massive YSOs in the LMC
• The roles of stellar feedback and galactic environment in star forming molecular clouds
• Photometric determination of the mass accretion rate of pre-main sequence stars. IV. Recent star formation in NGC 602
• Photometric determination of the mass accretion rates of pre-main sequence stars. V. Recent star formation in the 30 Dor nebula
• Deep GeMS/GSAOI near-infrared observations of N159W in the Large Magellanic Cloud
• Young and embedded clusters in Cygnus-X: evidence for building up the IMF?
• ${\mathcal{Q}}^{+}$: Characterising the structure of young star clusters
• Discovery of X-ray emission from young suns in the Small Magellanic Cloud
• Young open clusters in the galactic star forming region NGC 6357
• A rare early-type star revealed in the Wing of the Small Magellanic Cloud
• CO(2-1) Survey at 9 parsec resolution in the SMC
• The Core Mass Function Across Galactic Environments. III. Massive Protoclusters
• On the Dispersal of Young Stellar Hierarchies
• A discovery of young stellar objects in older clusters of the Large Magellanic Cloud
• Hubble Tarantula Treasury Project - VI. Identification of Pre-Main-Sequence Stars using Machine Learning techniques
• Sequential Star Formation in the Young SMC Region NGC 602: Insights from ALMA
• Externally irradiated young stars in NGC 3603. A JWST NIRSpec catalogue of pre-main-sequence stars in a massive star formation region
• Measuring Young Stars in Space and Time -- II. The Pre-Main-Sequence Stellar Content of N44