Uncrowding R 136 from VLT-SPHERE extreme adaptive optics

Abstract

This paper presents the sharpest near-IR images of the massive cluster R136 to date, based on the extreme adaptive optics of the SPHERE focal instrument implemented on the ESO/VLT and operated in its IRDIS imaging mode. Stacking-up a few hundreds of short exposures in J and Ks spectral bands over a FoV of 10.9"x12.3" centered on the R136a1 stellar component, enabled us to carry a refined photometric analysis of the core of R136. We detected 1110 and 1059 sources in J and Ks images respectively with 818 common sources. Thanks to better angular resolution and dynamic range, we found that more than 62.6% (16.5%) of the stars, detected both in J and Ks data, have neighbours closer than 0.2" (0.1"). Among resolved and detected sources R136a1 and R136c have visual companions and R136a3 is resolved as two stars separated by 59mas. The new set of detected sources were used to re-assess the age and extinction of R136 based on 54 spectroscopically stars that have been recently studied with HST slit-spectroscopy. Over 90% of these 54 sources identified visual companions (closer than 0.2"). We found the most probable age and extinction for these sources within the photometric and spectroscopic error-bars. Additionally, using PARSEC evolutionary isochrones and tracks, we estimated the stellar mass range for each detected source (common in J and K data) and plotted the generalized histogram of mass (MF with error-bars). Using SPHERE data, we have gone one step further and partially resolved and studied the IMF covering mass range of (3-300) Msun at the age of 1 and 1.5 Myr. The density in the core of R136 is estimated and extrapolated in 3D and larger radii (up to 6pc). We show that the stars in the core are still unresolved due to crowding, and the results we obtained are upper limits. Higher angular resolution is mandatory to overcome these difficulties.

Version2, 15 pages, 17 figures, 5 tables, Accepted to A&A

References in corpus (8)

• An eclipsing binary distance to the Large Magellanic Cloud accurate to 2 per cent
• The R136 star cluster hosts several stars whose individual masses greatly exceed the accepted 150 Msun stellar mass limit
• The R136 star cluster dissected with Hubble Space Telescope/STIS. I. Far-ultraviolet spectroscopic census and the origin of HeII 1640 in young star clusters
• The formation of secondary stellar generations in massive young star clusters from rapidly cooling shocked stellar winds
• The extinction law inside the 30 Doradus nebula
• The central density of R136 in 30 Doradus
• Search for cool giant exoplanets around young and nearby stars - VLT/NaCo near-infrared phase-coronagraphic and differential imaging
• VLT/SPHERE deep insight of NGC 3603's core: Segregation or confusion?

Cited by in corpus (10)

• SPHERE: the exoplanet imager for the Very Large Telescope
• The R136 star cluster dissected with Hubble Space Telescope/STIS. III. The most massive stars and their clumped winds
• The R136 star cluster dissected with Hubble Space Telescope/STIS. II. Physical properties of the most massive stars in R136
• Mapping the core of the Tarantula Nebula with VLT-MUSE: I. Spectral and nebular content around R136
• Forming clusters within clusters: How 30 Doradus recollapsed and gave birth again
• Constraints on the multiplicity of the most massive stars known: R136 a1, a2, a3, and c
• I3T: Intensity Interferometry Imaging Telescope
• High contrast and resolution near infrared photometry of the core of R136
• Extinction towards the cluster R136 in the Large Magellanic Cloud: An extinction law from the near-infrared to the ultraviolet
• Extreme adaptive optics astrometry of R136. Searching for high proper motion stars