The Planck submillimeter properties of Galactic high-mass star forming regions: dust temperatures, luminosities, masses and Star Formation Efficiency

TL;DR

This study combines Planck and IRAS data to analyze the physical properties of massive star-forming regions, revealing how star formation efficiency varies across the Galaxy and providing diagnostic tools for identifying such regions.

Contribution

It introduces a comprehensive method to estimate dust temperatures, masses, and luminosities of massive star-forming regions using combined Planck and IRAS data, and investigates star formation efficiency across the Galaxy.

Findings

Star formation efficiency peaks at 2-4.5 kpc from the Galactic center.

SFE remains constant up to 9 kpc and then declines linearly.

Diagnostic colors are proposed for identifying massive star formation sites.

Abstract

Massive star formation occurs in the interior of giant molecular clouds (GMC) and proceeds through many stages. In this work, we focus on massive young stellar objects (MYSOs) and Ultra-Compact HII regions (UCHII), where the former are enshrouded in dense envelopes of dust and gas, which the latter have begun dispersing. By selecting a complete sample of MYSOs and UCHII from the Red MSX Source (RMS) survey data base, we combine Planck and IRAS data and build their Spectral Energy Distributions (SEDs). With these, we estimate the physical properties (dust temperatures, mass, luminosity) of the sample. Because the RMS database provides unique solar distances, it also allows investigating the instantaneous Star Formation Efficiency (SFE) as a function of Galactocentric radius. We find that the SFE increase between 2 and 4.5 kpc, where it reaches a peak, likely in correspondence of the accumulation of molecular material at the end of the Galactic bar. It then stays approximately constant up to 9 kpc, after which it linearly declines, in agreement with predictions from extragalactic studies. This behavior suggests the presence of a significant amount of undetected molecular gas at R$_G$ $>$ 8 kpc. Finally we present diagnostic colors that can be used to identify sites of massive star formation.