Two Remarkable Spectroscopic Categories of Young O Stars from the VLT-FLAMES Tarantula Survey

TL;DR

This study identifies two unique categories of young O stars in the VLT-FLAMES Tarantula Survey: rapid rotators likely to be runaways, and Vz stars near the ZAMS, indicating their extreme youth.

Contribution

It reveals the spectral and spatial characteristics of two special O star categories, providing new insights into their nature and distribution in 30 Doradus.

Findings

Rapid rotators are distributed around cluster peripheries, suggesting runaway stars.

Vz stars are concentrated in ionizing clusters and star-forming regions, indicating extreme youth.

Radial velocities support the runaway hypothesis for rapid rotators.

Abstract

The spectral and spatial characteristics of two special categories of O stars found in the VFTS dataset are presented. One of them comprises very rapid rotators, including several more extreme than any previously known. These objects are distributed around the peripheries of the main 30 Doradus clusters, suggesting a runaway nature for which their radial velocities already provide preliminary supporting evidence. The other category consists of a large number of Vz stars, previously hypothesized on spectroscopic grounds to be on or very near the ZAMS. Their distribution is the inverse of that of the rapid rotators: the Vz are strongly concentrated to the ionizing clusters, plus a newly recognized band of recent and current star formation to the north, which provides strong circumstantial evidence for their extreme youth.