Visual extinction towards the Omega Nebula (M17) and the ionization of nitrogen in the nebula

Glushkov, Yu. I.; Есипов, В. Ф.; Kondrat'eva, L. N.

doi:10.1134/1.1850204

Cited by 4 publications

(5 citation statements)

References 6 publications

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“…from * is computed assuming an electron temperature of T e = 10 4 K and an electron density of n e = 3 × 10 3 cm −3 . This exercise results in a considerable total visual extinction of A V ; 8, which is agreeable with that found by Glushkov et al (2005) and Boersma et al (2018).…”

Section: Co 2 /H 2 O-ice Absorption Co Gas and Line Emissionsupporting

confidence: 91%

JWST: Deuterated PAHs, PAH Nitriles, and PAH Overtone and Combination Bands. I. Program Description and First Look

Boersma,

Allamandola,

Esposito

et al. 2023

ApJ

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A first look is taken at the NIRSpec 1–5 μm observations from James Webb Space Telescope program 1591 that targets seven objects along the low-mass stellar life cycle with polycyclic aromatic hydrocarbon (PAH) emission. Spectra extracted from a 1.″5 radius circular aperture are explored, showing a wealth of features, including the 3 μm PAH complex, the PAH continuum, and atomic and molecular emission lines from H i, He, H2, and other species. CO2- and H2O-ice absorption and CO emission is also seen. Focusing on the bright-PDR position in M17, the PAH CH stretch falls at 3.29 μm (FWHM = 0.04 μm). Signs of its 1.68 μm overtone are confused by line emission in all targets. Multicomponent decomposition reveals a possible aliphatic deuterated PAH feature centered at 4.65 μm (FWHM = 0.02 μm), giving [D/H]alip. = 31% ± 12.7%. However, there is little sign of its aromatic counterpart between 4.36 and 4.43 μm. There is also little sign of PAH nitrile emission between 4.34 and 4.39 μm. A PAH continuum rises from ∼1 to 3.2 μm, after which it jumps by about a factor of 2.5 at 3.6 μm, with bumps at 3.8, 4.04, and 4.34 μm adding structure. The CO2 absorption band in M17 is matched with 10:1 H2O:CO2 ice at 10 K. The v = 0 pure rotational molecular hydrogen population diagram reveals >2200 K UV-pumped gas. The hydrogen Pfund series runs from levels 10 to >30. Considering Brα/Brβ = 0.381 ± 0.01966 and Case B recombination results in A V ≃ 8. CO emission in IRAS 21282+5050 originates from 258 K gas. In-depth spectral–spatial analysis of all features and targets is planned for a series of forthcoming papers.

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Section: Co 2 /H 2 O-ice Absorption Co Gas and Line Emissionsupporting

confidence: 91%

JWST: Deuterated PAHs, PAH Nitriles, and PAH Overtone and Combination Bands. I. Program Description and First Look

Boersma,

Allamandola,

Esposito

et al. 2023

ApJ

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“…Therefore, the main reason why the large- jiri 1968;Clayton et al 1985). Consistent with this are measurements towards M 17 that show smaller visual extinctions varying across M 17 N with A V values between ∼0.4 and ∼6 magnitudes, and larger A V values between ∼6.5 and ∼14.5 magnitudes across M 17 S. (Ando et al 2002;Glushkov et al 2005).…”

Section: Comparing Sofia Images To Previousmentioning

confidence: 52%

“…These effects are likely due to the fact that the overall extinction towards M 17 N is far less than M 17 S, as evidenced by the presence of optical and Hα emission only associated with M 17 N (e.g., Ishida & Kawajiri 1968;Clayton et al 1985). Consistent with this are measurements towards M 17 that show smaller visual extinctions varying across M 17 N with A V values between ∼0.4 and ∼6 magnitudes, and larger A V values between ∼6.5 and ∼14.5 magnitudes across M 17 S. (Ando et al 2002;Glushkov et al 2005). (Wilson et al 2003), is shown as a reference for the location of the center of the M 17 SW molecular cloud (dotted line).…”

mentioning

confidence: 86%

Surveying the Giant H ii Regions of the Milky Way with SOFIA. II. M17

Lim

Buizer

Radomski

2020

ApJ

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We present our second set of results from our mid-infrared imaging survey of Milky Way Giant H II regions. We used the FORCAST instrument on the Stratospheric Observatory For Infrared Astronomy to obtain 20 and 37 µm images of the central ∼10 ×10 area of M 17. We investigate the small-and large-scale properties of M 17 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, UC 1, is determined to be 64 M . We resolve the extended mid-infrared emission from the KW Object, and suggest that the angle of this extended emission is influenced by outflow. IRS 5 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 M 17 at 20 µm is significantly affected by contamination from the [SIII] emission line from the ionized gas of the giant H II region. Finally, a number of potential evolutionary tracers yield a consistent picture suggesting that the southern bar of M 17 is likely younger than the northern bar.

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“…Early low-resolution measurements (e.g., Dickel 1968;Ishida & Kawajiri 1968) yielded an east-west gradient of the extinction, starting at A V ¼ 1 mag toward the H ii region and reaching a maximum of A V ¼ 7 mag toward the central absorbing dust filament in front of the cluster. Glushkov et al (2005) presented the most detailed measurements and derived A V values for the eastern, optically bright part of the nebula of 2-6 mag. This minimum extinction of A V $ 1-2 mag located in front of the H ii region is in good agreement with Galactic models that predict values of A V $ 2:7 mag at a distance of 2 kpc in the direction of M17 (Bahcall & Soneira 1980).…”

Section: The Extinction Toward M17mentioning

confidence: 99%

The Stellar Population of M17

Hoffmeister

Chini

Scheyda

et al. 2008

Astrophysical Journal

105

151

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The stellar content of M17 has been investigated by multicolor photometry and spectroscopy. Various independent estimates yield a distance of 2:1 AE 0:2 kpc. The ratio of total-to-selective extinction is R ¼ 3:9. Within a projected area of 3:6 ; 3:7 pc, there are several thousand stars. About 74% of them show infrared excess suggesting the presence of dense circumstellar material; the excess frequency is higher for fainter stars. The number of spectroscopically classified exciting stars could be enlarged from 13 to 46. The two central O4 stars are both spectroscopic binaries; multiplicity of other early O-type stars could also be established, increasing the number of high-mass stars even further. Our data suggest at least two episodes of star formation: There are about 500 ZAMS sources (2 < A V < 7)-among them many spectroscopically classified OB stars and a significant fraction of lower mass sources with infrared excess ($25%) and X-ray emission ($6%). About 3350 heavily reddened sources with 10 < A V < 40) are most likely deeply embedded pre-main-sequence objects with an age of less than 5 ; 10 5 yr. This group contains about 47% sources with infrared excess and 12% X-ray emitters. Cluster members later than about A0 have not yet reached the main sequence. In addition, a group of 647 protostellar candidates (1:5 < K À L < 6:9) has been detected in the cluster center as well as in the northern and southwestern bar. This population of accreting protostars argues in favor of ongoing star formation triggered by the central O stars in M17.

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Visual extinction towards the Omega Nebula (M17) and the ionization of nitrogen in the nebula

Cited by 4 publications

References 6 publications

JWST: Deuterated PAHs, PAH Nitriles, and PAH Overtone and Combination Bands. I. Program Description and First Look

JWST: Deuterated PAHs, PAH Nitriles, and PAH Overtone and Combination Bands. I. Program Description and First Look

Surveying the Giant H ii Regions of the Milky Way with SOFIA. II. M17

The Stellar Population of M17

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