Surveying the Giant HII Regions of the Milky Way with SOFIA: II. M17

Abstract

We present our second set of results from our mid-infrared imaging survey of Milky Way Giant HII regions. We used the FORCAST instrument on the Stratospheric Observatory For Infrared Astronomy to obtain 20 and 37$\mu$m images of the central ~10'X10' area of M17. We investigate the small- and large-scale properties of M17 using our data in conjunction with previous multi-wavelength observations. The spectral energy distributions of individual compact sources were constructed with Spitzer-IRAC, SOFIA-FORCAST, and Herschel-PACS photometry data and fitted with massive young stellar object (MYSO) models. Seven sources were found to match the criteria for being MYSO candidates, four of which are identified here for the first time, and the stellar mass of the most massive object, UC1, is determined to be 64 solar mass. We resolve the extended mid-infrared emission from the KW Object, and suggest that the angle of this extended emission is influenced by outflow. IRS5 is shown to decrease in brightness as a function of wavelength from the mid- to far-infrared, and has several other indicators that point to it being an intermediate mass Class II object and not a MYSO. We find that the large-scale appearance of emission in M17 at 20$\mu$m is significantly affected by contamination from the [SIII] emission line from the ionized gas of the Giant HII region. Finally, a number of potential evolutionary tracers yield a consistent picture suggesting that the southern bar of M17 is likely younger than the northern bar.

25 pages, 16 figures, 9 tables, accepted for publication in ApJ

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Cited by in corpus (13)

• PHANGS-JWST First Results: A statistical view on bubble evolution in NGC628
• M17 MIR: A massive protostar with multiple accretion Outbursts
• The Extraordinary Outburst in the Massive Protostellar System NGC6334I-MM1: Strong Increase in Mid-Infrared Continuum Emission
• Studying magnetic fields and dust in M17 using polarized thermal dust emission observed by SOFIA/HAWC+
• Gamma-ray observation towards the young massive star cluster NGC 6618 in the M17 region
• Massive pre-main-sequence stars in M17: $1^{\mathrm{st}}$ and $2^{\mathrm{nd}}$ overtone CO bandhead emission and the thermal infrared
• Massive pre-main-sequence stars in M17 -- Modelling hydrogen and dust in MYSO disks
• Surveying the Giant HII Regions of the Milky Way with SOFIA: IV. Sgr D, W42, and a Reassessment of the Giant HII Region Census
• Surveying the Giant HII Regions of the Milky Way with SOFIA: III. W49A
• New Massive Contact Twin Binary in a Radio-quiet HII Region Associated with the M17 Complex
• Spatial distribution of NH2D in massive star-forming regions
• Surveying the Giant HII Regions of the Milky Way with SOFIA: V. DR7 and K3-50
• The population of compact radio sources in M 17