Integral-field near-infrared spectroscopy of two blue dwarf galaxies: NGC 5253 and He 2-10

TL;DR

This study uses near-infrared integral field spectroscopy to analyze the interstellar medium and star formation processes in two nearby dwarf galaxies, revealing detailed spatial distributions, kinematics, and feedback effects associated with star formation.

Contribution

It provides the first detailed spatially resolved NIR spectroscopic analysis of the ISM and star formation in NGC 5253 and He 2-10, highlighting feedback and shock contributions.

Findings

ISM mostly photo-excited with some shock regions

Molecular gas shows consistent morphology and velocity in He 2-10

High turbulence driven by star formation activity

Abstract

We present integral field spectroscopy in the near infrared (NIR) of He 2-10 and NGC 5253, two well known nearby dwarf irregular galaxies showing high star-formation rates. Our data provide an unprecedented detailed view of the interstellar medium and star formation in these galaxies, allowing us to obtain spatially resolved information from the NIR emission and absorption line tracers. We study the spatial distribution and kinematics of different components of the interstellar medium (ISM) mostly through the Bracket series lines, the molecular hydrogen spectrum, [FeII] emission, and CO absorptions. Although the ISM is mostly photo-excited, as derived by the [FeII]/Bry and H2 line ratios, some regions corresponding to non-thermal radio sources show a [FeII]/Bry excess due to a significant contribution of SN driven shocks. In He 2-10 we find that the molecular gas clouds, as traced by CO(2-1) and H2 infrared line, show consistent morphologies and velocities when studied with the two different tracers. Moreover, there is a clear association with the youngest super star clusters as traced by the ionized gas. In the same galaxy we observe a cavity depleted of gas, which is surrounded by some of the most active regions of star formation, that we interpret as a signature of feedback-induced star formation from older episodes of star formation. Finally, we measured high turbulence in the ISM of both galaxies, sigma~30-80 km/s, driven by the high star-formation activity.