The Origin of OB Clusters: From 10 pc to 0.1 pc

TL;DR

This study uses millimeter observations to explore the structure and formation processes of OB clusters, revealing filamentary gas structures, molecular clumps, and potential pathways for mass accretion in a high-mass star-forming region.

Contribution

It provides high-resolution imaging of the gas filaments and cores around an OB cluster, highlighting their role in cluster formation and mass accretion mechanisms.

Findings

Filaments show regularly spaced molecular clumps.

Central region contains a dense 3 pc structure with a 200 M$_{ ext{sun}}$ OB cluster.

No significant polarized emission detected in the inner 1 pc.

Abstract

We observe the 1.2 mm continuum emission around the OB cluster forming region G10.6-0.4, using the IRAM 30m telescope MAMBO-2 bolometer array and the Submillimeter array. Comparison of the Spitzer 24 $\mu$m and 8 $\mu$m images with our 1.2 mm continuum maps reveals the ionization front of an HII region, the photon-dominated layer, and several 5 pc scale filaments following the outer edge of the photon-dominated layer. The filaments, which are resolved in the MAMBO-2 observations, show regularly spaced parsec-scale molecular clumps, embedded with a cluster of submillimeter molecular cores as shown in the SMA 0.87 mm observations. Toward the center of the G10.6-0.4 region, the combined SMA+IRAM 30m continuum image reveals several, parsec-scale protrusions. They may continue down to within 0.1 pc of the geometric center of a dense 3 pc size structure, where a 200 M$_{\odot}$ OB cluster resides. The observed filaments may facilitate mass accretion onto the central cluster--forming region in the presence of strong radiative and mechanical stellar feedbacks. Their filamentary geometry may also facilitate fragmentation. We did not detect any significant polarized emission at 0.87 mm in the inner 1 pc region with the SMA.