High contrast and resolution near infrared photometry of the core of R136

TL;DR

This study provides the most detailed near-infrared photometry of R136's core using adaptive optics, revealing a large number of sources, detailed mass function slopes, and evidence of ongoing star formation in the region.

Contribution

It offers the deepest and sharpest near-infrared imaging of R136's core, increasing source resolution and analyzing the mass function and star formation activity with new adaptive optics data.

Findings

Detected 1499 sources within the core, with 76% having close visual companions.

Mass function slopes vary with age, radius, and mass range, being about 0.3 dex steeper for 10-300 M_sun than for 3-300 M_sun.

67% of sources in the outer region show signs of ongoing star formation unrelated to R136.

Abstract

We present the sharpest and deepest near infrared photometric analysis of the core of R136, a newly formed massive star cluster at the centre of the 30 Doradus star forming region in the Large Magellanic Cloud. We used the extreme adaptive optics of the SPHERE focal instrument implemented on the ESO Very Large Telescope and operated in its IRDIS imaging mode, for the second time with longer exposure time in the H- and K filters. Our aim was to (i) increase the number of resolved sources in the core of R136, and (ii) to compare with the first epoch to classify the properties of the detected common sources between the two epochs. Within the field of view (FOV) of 10.8"x12.1" (2.7pc x3.0pc), we detected 1499 sources in both H and K filters, for which 76% of these sources have visual companions closer than 0.2". The larger number of detected sources, enabled us to better sample the mass function (MF). The MF slopes are estimated at ages of 1, 1.5 and 2 Myr, at different radii, and for different mass ranges. The MF slopes for the mass range of 10-300 solar-mass are about 0.3 dex steeper than the mass range of 3-300 solar-mass, for the whole FOV and different radii. Comparing the JHK colours of 790 sources common in between the two epochs, 67% of detected sources in the outer region (r >3") are not consistent with evolutionary models at 1-2 Myr and with extinctions similar to the average cluster value, suggesting an origin from ongoing star formation within 30 Doradus, unrelated to R136.