Integral field near-infrared spectroscopy of II Zw 40

TL;DR

This study uses near-infrared integral field spectroscopy to analyze the interstellar medium and star formation in the starburst galaxy II Zw 40, revealing detailed spatial and kinematic properties of its giant HII region and associated clusters.

Contribution

First detailed near-infrared integral field spectroscopic analysis of II Zw 40's interstellar medium and star formation regions.

Findings

Giant HII region extends over 400 pc.

Main ionizing cluster resembles 30 Doradus in LMC.

H2 and [FeII] emissions have different spatial distributions.

Abstract

We present integral field spectroscopy in the near-infrared of the nearby starburst galaxy IIZw40. Our new observations provide an unprecedented detailed view of the interstellar medium and star formation of this galaxy. The radiation emitted by the galaxy is dominated by a giant HII region, which extends over an area of more than 400 pc in size. A few clusters are present in this area, however one in particular appears to be the main source of ionizing photons. We derive the properties of this object and compare them with those of the 30 Doradus cluster in the Large magellanic cloud (LMC). We study the spatial distribution and velocity field of different components of the inetrstellar medium (ISM), mostly through the Bracket series lines, the molecular hydrogen spectrum, and [FeII]. We find that [FeII] and H2 are mostly photon excited, but while the region emitting [FeII] is almost coincident with the giant HII region observed in the lines of atomic H and He, the H2 has a quite different distribution in space and velocity. The age of the stellar population in the main cluster is such that no supernova (SN) should be present yet so that the gas kinematics must be dominated by the young stars. We do not see, in the starbursting region, any geometrical or dynamical structure that can be related to the large scale morphology of the galaxy.