Four highly luminous massive star forming regions in the Norma Spiral Arm.: I. Molecular gas and dust observations

TL;DR

This study presents molecular line and dust continuum observations of four luminous high-mass star forming regions, revealing their physical properties, core structures, and the role of dynamical friction in star migration.

Contribution

It provides detailed physical characterization of massive star forming cores and highlights the importance of dynamical friction in stellar mass segregation.

Findings

Cores have radii ~0.5 pc and masses ~5x10^3 Msun.

Density profiles follow power-law indices 1.6-1.9.

Dynamical friction influences high-mass star migration.

Abstract

We report molecular line and dust continuum observations, made with the SEST telescope, towards four young high-mass star forming regions associated with highly luminous (L> 6x10^5 Lsun) IRAS sources (15290-5546, 15502-5302, 15567-5236 and 16060-5146). Molecular emission was mapped in lines of CS (J=2-1, 3-2 and 5-4), SiO (J=2-1 and 3-2), CH3OH (Jk=3k-2k and 2k-1k), and C34S (J=3-2). In addition, single spectra at the peak position were taken in the CO, 13CO and C18O (J=1-0) lines. We find that the luminous star forming regions are associated with molecular gas and dust structures with radii of typically 0.5 pc, masses of ~5x10^3 Msun, column densities of ~5x10^{23} cm^{-2}, molecular hydrogen densities of typically ~2x10^5 cm^{-3} and dust temperatures of ~40 K. The 1.2 mm dust continuum observations further indicate that the cores are centrally condensed, having radial density profiles with power-law indices in the range 1.6-1.9. We find that under these conditions dynamical friction by the gas plays an important role in the migration of high-mass stars towards the central core region, providing an explanation for the observed stellar mass segregation within the cores.