Optical IFU observations of gas pillars surrounding the super star cluster NGC 3603

TL;DR

This study uses optical IFU observations to analyze gas pillars near NGC 3603, revealing complex emission line structures, high densities, and turbulent layers driven by stellar winds, advancing understanding of star cluster feedback.

Contribution

First detailed optical IFU analysis of gas pillars around NGC 3603, identifying turbulent mixing layers and high-density photoevaporative flows.

Findings

Broad and narrow emission components indicate turbulence and photoevaporation.

High ionized gas densities (>10,000 cm^-3) found in pillars.

Velocity offsets suggest complex gas dynamics near star cluster.

Abstract

We present optical integral field unit (IFU) observations of two gas pillars surrounding the Galactic young massive star cluster NGC 3603. The high S/N and spectral resolution of these data have allowed us to accurately quantify the H-alpha, [NII] and [SII] emission line shapes, and we find a mixture of broad (FWHM~70-100 km/s) and narrow (<50 km/s) components. The broad components are found close to the edges of both pillars, suggesting that they originate in turbulent mixing layers (TMLs) driven by the effect of the star cluster wind. Both pillars exhibit surprisingly high ionized gas densities of >10000 cm-3. In one pillar we found that these high densities are only found in the narrow component, implying it must originate from deeper within the pillar than the broad component. From this, together with our kinematical data, we conclude that the narrow component traces a photoevaporation flow, and that the TML forms at the interface with the hot wind. On the pillar surfaces we find a consistent offset in radial velocity between the narrow (brighter) components of H-alpha and [NII] of ~5-8 km/s, for which we were unable to find a satisfactory explanation. We urge the theoretical community to simulate mechanical and radiative cloud interactions in more detail to address the many unanswered questions raised by this study.