On Collision Course: The Nature of the Binary Star Cluster NGC 2006 / SL 538
arXiv:1811.07980 · doi:10.1051/0004-6361/201834103
Abstract
The LMC hosts a rich variety of star clusters seen in close projected proximity. Ages have been derived for few of them showing differences up to few million years, hinting at being binary star clusters. However, final confirmation needs to be done through spectroscopic analysis. Here we focus on the LMC cluster pair NGC2006-SL538 and aim to determine whether the star cluster pair is a bound entity (binary star cluster) or a chance alignment. Using the MIKE echelle spectrograph at LCO we have acquired integrated-light spectra for each cluster. We have measured radial velocities by two methods: a) direct line profile measurement yields v km/s for NGC2006 and km/s for SL538. b) By comparing observed spectra with synthetic bootstrapped spectra yielding km/s for NGC2006 and km/s for SL538. Finally when spectra are directly compared, we find a km/s. Full-spectrum SED fits reveal that the stellar population ages lie in the range 13-21 Myr with a metallicity of Z=0.008. We find indications for differences in the chemical abundance patterns as revealed by the helium absorption lines between the two clusters. The dynamical analysis shows that the two clusters are likely to merge within the next 150 Myr. The NGC2006-SL538 cluster pair shows radial velocities, stellar population and dynamical parameters consistent with a gravitational bound entity. We conclude that this is a genuine binary cluster pair, and we propose that their differences in ages and stellar population chemistry is most likely due to variances in their chemical enrichment history within their environment. We suggest that their formation may have taken place in a loosely bound star-formation complex which saw initial fragmentation but then had its clusters become a gravitationally bound pair by tidal capture.
arXiv commentAccepted for publication in Astronomy & Astrophysics. 15 pages, 10 figures in low resolution
References in corpus (21)
- Starburst99: Synthesis Models for Galaxies with Active Star Formation
- Cosmic-Ray Rejection by Laplacian Edge Detection
- Multiple populations in globular clusters. Lessons learned from the Milky Way globular clusters
- An eclipsing binary distance to the Large Magellanic Cloud accurate to 2 per cent
- New Understanding of Large Magellanic Cloud Structure, Dynamics and Orbit from Carbon Star Kinematics
- Optimization of Starburst99 for Intermediate-Age and Old Stellar Populations
- The Effects of Stellar Rotation. II. A Comprehensive Set of Starburst99 Models
- A Library of Theoretical Ultraviolet Spectra of Massive, Hot Stars for Evolutionary Synthesis
- The nucleus of the Sagittarius dSph galaxy and M54: a window on the process of galaxy nucleation
- A new library of theoretical stellar spectra with scaled-solar and alpha-enhanced mixtures
- The dynamical evolution of stellar super-clusters
- A Possible Formation Scenario for the Ultra-Massive Cluster W3 in NGC 7252
- A statistical study of binary and multiple clusters in the LMC
- From the Top Down and Back Up Again: Star Cluster Structure from Hierarchical Star Formation
- A parametric study on the formation of extended star clusters and ultra-compact dwarf galaxies
- The Most Exciting Massive Binary Cluster in NGC 5128: Clues to the Formation of Globular Clusters
- The evolution of binary star clusters and the nature of NGC2136/NGC2137
- Blood ties: the real nature of the LMC binary globular clusters NGC 2136 and NGC 2137
- CCD photometric and mass function study of 9 young Large Magellanic Cloud star clusters
- Binary open clusters in the Milky Way: photometric and spectroscopic analysis of NGC 5617 and Trumpler 22
- Simulations of Fractal Star Cluster Formation: I. New Insights for Measuring Mass Segregation of Star Clusters with SubStructure