Ionizing stellar population in the disc of NGC 3310 - II. The Wolf-Rayet population

TL;DR

This study uses integral field spectroscopy to analyze the Wolf-Rayet star population in NGC 3310, revealing insights into their distribution, properties, and potential role in gamma-ray burst progenitors, while highlighting discrepancies with stellar models.

Contribution

It provides detailed spatially resolved analysis of WR stars in NGC 3310 and explores the impact of binaries, dust, and environment on WR observables and their connection to GRBs.

Findings

WNL/(WNL+O) ratio aligns with empirical relations after dust correction.

Accounting for binaries and photon leakage improves model-observation agreement.

Galaxy interactions may foster environments where WRs can produce GRBs.

Abstract

We use integral field spectroscopy to study in detail the Wolf-Rayet (WR) population in NGC 3310, spatially resolving 18 star-forming knots with typical sizes of 200-300 pc in the disc of the galaxy hosting a substantial population of WRs. The detected emission in the so-called blue bump is attributed mainly to late-type nitrogen WRs (WNL), ranging from a few dozens to several hundreds of stars per region. Our estimated WNL/(WNL+O) ratio is comparable to reported empirical relations once the extinction-corrected emission is further corrected by the presence of dust grains inside the nebula that absorb a non-negligible fraction of UV photons. Comparisons of observables with stellar population models show disagreement by factors larger than 2-3. However, if the effects of interacting binaries and/or photon leakage are taken into account, observations and predictions tend to converge. We estimate the binary fraction of the \hii regions hosting WRs to be significant in order to recover the observed X-ray flux, hence proving that the binary channel can be critical when predicting observables. We also explore the connection of the environment with the current hypothesis that WRs can be progenitors to long-duration gamma-ray bursts (GRBs). Galaxy interactions, which can trigger strong episodes of star formation in the central regions, may be a plausible environment where WRs may act as progenitors of GRBs. Finally, even though the chemical abundance is generally homogeneous, we also find weak evidence for rapid N pollution by WR stellar winds at scales of ~ 200 pc.