A very young component in the pre-eminent starburst region of the Small Magellanic Cloud

TL;DR

This study investigates the very young, high-excitation H II region N66A in the Small Magellanic Cloud, revealing its physical characteristics and identifying its main exciting star as an O8 type, contributing to understanding massive star formation.

Contribution

It provides the first spectral classification of N66A's main star and characterizes its physical properties within the context of star formation in the Magellanic Clouds.

Findings

N66A hosts a main sequence O8 star.

N66A is a high-excitation, very young H II region.

N66A represents a recent massive star formation event.

Abstract

We present a study of the compact H II region N66A in the SMC pre-eminent starburst region N66/NGC346. Despite extensive research on various components of the N66/NGC346 complex, few studies have so far focused on N66A, which is a special object in the whole complex and therefore deserves scrutiny. The study of this compact H II region and its fellow objects seems important in the framework of massive star formation in the Magellanic Clouds. This analysis is based mainly on our optical ESO NTT observations, both imaging and spectroscopy, coupled with archive HST ACS data and Spitzer infrared images (IRAC 3.6, 4.5, 5.8, and 8.0 microns). We derive a number of physical characteristics of the compact H II region N66A. Moreover, we present the spectral classification of the main exciting star of N66A for the first time using spectroscopy. Its spectral features indicate a main sequence massive star of type O8. We compare this result with that based on the stellar Lyman continuum flux estimated from the ionized gas H-beta flux. The compact H II region belongs to a rare class of H II regions in the Magellanic Clouds, called High-excitation Blobs (HEBs). N66A most probably represents a very young massive star formation event in the N66 complex, which has a range of ages.