Revealing the nebular properties and Wolf-Rayet population of IC10 with Gemini/GMOS

TL;DR

This study uses Gemini/GMOS observations to analyze IC10's nebular properties and Wolf-Rayet star population, revealing a total of 29 WR stars and insights into its metallicity and star formation characteristics.

Contribution

It provides the first comprehensive survey of IC10's Wolf-Rayet population, including new WN stars, and revises its nebular metallicity and star formation rate.

Findings

IC10 has a star formation rate of 0.045 Msun/yr.

Revised nebular oxygen abundance is log(O/H)+12=8.40.

Total Wolf-Rayet stars in IC10 is 29, with a WC/WN ratio around 0.7-1.0.

Abstract

We present a deep imaging and spectroscopic survey of the Local Group irregular galaxy IC10 using Gemini North and GMOS to unveil its global Wolf-Rayet (WR) population. We obtain a star formation rate (SFR) of 0.045 +/- 0.023 Msun/yr, for IC10 from the nebular Halpha luminosity, which is comparable to the SMC. We also present a revised nebular oxygen abundance of log(O/H) + 12 = 8.40 +/- 0.04, comparable to the LMC. It has previously been suggested that for IC10 to follow the WR subtype-metallicity dependance seen in other Local Group galaxies, a large WN population awaits discovery. Our search revealed 3 new WN stars, and 6 candidates awaiting confirmation, providing little evidence to support this claim. The new global WR star total of 29 stars is consistent with the LMC population when scaled to the reduced SFR of IC10. For spectroscopically confirmed WR stars, the WC/WN ratio is lowered to 1.0, however including all potential candidates, and assuming those unconfirmed to be WN stars, would reduce the ratio to ~0.7. We attribute the high WC/WN ratio to the high star formation surface density of IC10 relative to the Magellanic Clouds, which enhances the frequency of high mass stars capable of producing WC stars.