The VLT-FLAMES Tarantula Survey XIV. The O-Type Stellar Content of 30 Doradus

TL;DR

This study provides detailed spectral classifications for 352 O-B0 stars in 30 Doradus, revealing new rare spectral types, rapid rotators, and young stellar populations, enhancing understanding of massive star evolution in starburst regions.

Contribution

It offers the first comprehensive spectral classification of a large sample of O-B0 stars in 30 Doradus, identifying new spectral subtypes and insights into stellar evolution and cluster dynamics.

Findings

Discovery of new O2-O3 spectral type stars.

Identification of extremely rapid rotators and their distribution.

Detection of a large fraction of V((fc)) class stars.

Abstract

Detailed spectral classifications are presented for 352 O-B0 stars in the VLT-FLAMES Tarantula Survey, of which 213 O-type are of sufficient quality for further morphological analysis. Among them, six subcategories of special interest are distinguished. (1) Several new examples of the earliest spectral types O2-O3 have been found. (2) A group of extremely rapidly rotating main-sequence objects has been isolated, including the largest $v\sin i$ values known, the spatial and radial-velocity distributions of which suggest ejection from the two principal ionizing clusters. (3) Several new examples of the evolved, rapidly rotating Onfp class show similar evidence. (4) No fewer than 48 members of the Vz category, hypothesized to be on or near the ZAMS, are found in this sample; in contrast to the rapid rotators, they are strongly concentrated to the ionizing clusters, supporting their interpretation as very young objects, as do their relatively faint absolute magnitudes. (5) A surprisingly large fraction of the main-sequence spectra belong to the recently recognized V((fc)) class, with C III emission lines of similar strength to the usual N III in V((f)) spectra; there are also six objects with very high-quality data but no trace of either mission feature, presenting new challenges to physical interpretations. (6) Five spectra with morphologically enhanced nitrogen lines have been detected. Absolute visual magnitudes have been derived for each star with individual extinction laws, and composite HRDs provide evidence of the multiple generations present in this field. Associations with X-ray sources are noted. Further analyses of this unique dataset underway will provide new insights into the evolution of massive stars and starburst clusters.