A Multiwavelength Look at Galactic Massive Star Forming Regions

Breanna A. Binder; Matthew S. Povich

doi:10.3847/1538-4357/aad7b2

paper

A Multiwavelength Look at Galactic Massive Star Forming Regions

arXiv:1808.00454 · doi:10.3847/1538-4357/aad7b2

Abstract

We present a multiwavelength study of 28 Galactic massive star-forming H II regions. For 17 of these regions, we present new distance measurements based on Gaia DR2 parallaxes. By fitting a multicomponent dust, blackbody, and power-law continuum model to the 3.6 $μ$ m through 10 mm spectral energy distributions, we find that $\sim 34$ % of Lyman continuum photons emitted by massive stars are absorbed by dust before contributing to the ionization of H II regions, while $\sim 68$ % of the stellar bolometric luminosity is absorbed and reprocessed by dust in the H II regions and surrounding photodissociation regions. The most luminous, infrared-bright regions that fully sample the upper stellar initial mass function (ionizing photon rates $N_{C} \geq 1 0^{50} s^{- 1}$ and dust-processed $L_{TIR} \geq 1 0^{6.8}$ L $_{⊙}$ ) have on average higher percentages of absorbed Lyman continuum photons ( $\sim$ 51%) and reprocessed starlight ( $\sim$ 82%) compared to less luminous regions. Luminous H II regions show lower average PAH fractions than less luminous regions, implying that the strong radiation fields from early-type massive stars are efficient at destroying PAH molecules. On average, the monochromatic luminosities at 8, 24, and 70 $μ$ m combined carry 94% of the dust-reprocessed $L_{TIR}$ . $L_{70}$ captures $\sim 52$ % of $L_{TIR}$ , and is therefore the preferred choice to infer the bolometric luminosity of dusty star-forming regions. We calibrate SFRs based on $L_{24}$ and $L_{70}$ against the Lyman continuum photon rates of the massive stars in each region. Standard extragalactic calibrations of monochromatic SFRs based on population synthesis models are generally consistent with our values.

arXiv commentAccepted to AAS Journals; 35 pages, 10 figures, 8 tables

A Multiwavelength Look at Galactic Massive Star Forming Regions

Abstract

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