An excess of massive stars in the local 30 Doradus starburst

TL;DR

This study investigates the recent star formation history and initial mass function in the 30 Doradus region, revealing an excess of very massive stars and a shallower IMF slope than the classical Salpeter value.

Contribution

It provides the first detailed spectroscopic analysis of massive stars in 30 Doradus, showing a higher-than-expected number of stars above 30 solar masses and a shallower IMF slope.

Findings

Star formation in 30 Doradus peaked about 8 million years ago.

There is a 32% excess of stars above 30 solar masses compared to Salpeter IMF predictions.

The IMF slope in the 15-200 solar mass range is shallower than the Salpeter value of 2.35.

Abstract

The 30 Doradus star-forming region in the Large Magellanic Cloud is a nearby analogue of large star-formation events in the distant Universe. We determine the recent formation history and the initial mass function (IMF) of massive stars in 30 Doradus based on spectroscopic observations of 247 stars more massive than 15 solar masses ($\mathrm{M}_\odot$). The main episode of massive star formation started about $8\,\mathrm{Myr}$ ago and the star-formation rate seems to have declined in the last $1\,\mathrm{Myr}$. The IMF is densely sampled up to $200\,\mathrm{M}_\odot$ and contains $32\pm12\%$ more stars above $30\,\mathrm{M}_\odot$ than predicted by a standard Salpeter IMF. In the mass range $15-200\,\mathrm{M}_\odot$, the IMF power-law exponent is $1.90^{+0.37}_{-0.26}$, shallower than the Salpeter value of 2.35.