A Multiwavelength Study of M17: The Spectral Energy Distribution and PAH Emission Morphology of a Massive Star Formation Region

Povich, Matthew S.; Stone, Jamie A.; Churchwell, E.; Zweibel, Ellen G.; Wolfire, M. G.; Babler, B.; Indebetouw, R.; Meade, M. R.; Whitney, B. A.

doi:10.1086/513073

Cited by 177 publications

(217 citation statements)

References 44 publications

(56 reference statements)

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“…There are other large, partially symmetrical and rich HII regions (in terms of their OB stellar content) that display a similar mid-IR color stratification: the Rosette Nebula (Kraemer et al 2003), the Trifid Nebula (Lefloch et al 1999;Rho et al 2006), and M 17 (Povich et al 2007). Furthermore, the multi-wavelength observations of the HII regions in the Galactic Plane, using the Spitzer GLIMPSE and MIPSGAL Legacy surveys Carey et al 2009) display overall a wide variety of complex morphologies, and contain many "bubble"-like objects with a similar color stratification as M 16 (Watson et al 2008(Watson et al , 2009), although they are smaller and driven by one or a few OB stars.…”

Section: Introductionmentioning

confidence: 98%

“…A first key to the interpretation of Spitzer images is the change in abundance and excitation of these small dust particles from molecular to ionized gas. Observations of nearby molecular clouds illuminated by O stars, where observations separate the H II photo-ionized gas layer from the neutral photo-dissociation region (PDR) show that the PAH bands, which are a characteristic of PDR mid-IR emission spectra, are strikingly absent from that of the H II layer (e.g., the Orion Bar and the M 17SW interface, Giard et al 1994;Cesarsky et al 1996b;Povich et al 2007). PAHs are quickly destroyed when matters flows across the ionization front.…”

Section: Introductionmentioning

confidence: 99%

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Tracing the energetics and evolution of dust withSpitzer: a chapter in the history of the Eagle Nebula

Flagey

Boulanger

Noriega-Crespo

et al. 2011

A&A

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Context. The Spitzer GLIMPSE and MIPSGAL surveys have revealed a wealth of details about the Galactic plane in the infrared (IR) with orders of magnitude higher sensitivity, higher resolution, and wider coverage than previous IR observations. The structure of the interstellar medium (ISM) is tightly connected to the countless star-forming regions. We use these surveys to study the energetics and dust properties of the Eagle Nebula (M 16), one of the best known star-forming regions. Aims. We present MIPSGAL observations of M 16 at 24 and 70 μm and combine them with previous IR data. The mid-IR image shows a shell inside the well-known molecular borders of the nebula, as in the ISO and MSX observations from 15 to 21 μm. The morphologies at 24 and 70 μm are quite different, and its color ratio is unusually warm. The far-IR image resembles the one at 8 μm that enhances the structure of the molecular cloud and the "pillars of creation". We use this set of IR data to analyze the dust energetics and properties within this template for Galactic star-forming regions. Methods. We measure IR spectral energy distributions (SEDs) across the entire nebula, both within the inner shell and the photodissociation regions (PDRs). We use the DUSTEM model to fit these SEDs and constrain the dust temperature, the dust-size distribution, and the radiation field intensity relative to that provided by the star cluster NGC 6611 (χ/χ 0 ). Results. Within the PDRs, the inferred dust temperature (∼35 K), the dust-size distribution, and the radiation field intensity (χ/χ 0 < 1) are consistent with expectations. Within the inner shell, the dust is hotter (∼70 K). Moreover, the radiation field required to fit the SED is larger than that provided by NGC 6611 (χ/χ 0 > 1). We quantify two solutions to this problem: (1) The size distribution of the dust in the shell is not that of interstellar dust. There is a significant enhancement of the carbon dust-mass in stochastically heated very small grains. (2) The dust emission arises from a hot (∼10 6 K) plasma where both UV and collisions with electrons contribute to the heating. Within this hypothesis, the shell SED may be fit for a plasma pressure p/k ∼ 5 × 10 7 K cm −3 . Conclusions. We suggest two interpretations for the M 16 inner shell: (1) The shell matter is supplied by photo-evaporative flows arising from dense gas exposed to ionized radiation. The flows renew the shell matter as it is pushed out by the pressure from stellar winds. Within this scenario, we conclude that massive-star forming regions such as M 16 have a major impact on the carbon dustsize distribution. The grinding of the carbon dust could result from shattering in grain-grain collisions within shocks driven by the dynamical interaction between the stellar winds and the shell. (2) We also consider a more speculative scenario where the shell is a supernova remnant. In this case, we would be witnessing a specific time in the evolution of the remnant where the plasma pressure and temperature would enable the remnant to coo...

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Tracing the energetics and evolution of dust withSpitzer: a chapter in the history of the Eagle Nebula

Flagey

Boulanger

Noriega-Crespo

et al. 2011

A&A

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“…Resolved observations of star-forming regions have shown that the VSG continuum strongly peaks inside H ii regions while PAH features dominate in photodissociation regions (PDRs) and get weaker nearer the core of H ii regions, where the molecules are thought to be destroyed by the intense radiation fields (e.g., Boulanger et al 1988;Giard et al 1994;Cesarsky et al 1996;Verstraete et al 1996;Povich et al 2007;Gordon et al 2008). However, neutral PAH emission has recently been reported inside H ii region (Compiègne et al 2007).…”

Section: Introductionmentioning

confidence: 99%

Mid-Infrared Spectral Indicators of Star Formation and Active Galactic Nucleus Activity in Normal Galaxies

Treyer¹,

Schiminovich²,

Johnson³

et al. 2010

ApJ

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We investigate the use of mid-infrared (MIR) polycyclic aromatic hydrocarbon (PAH) bands, the continuum, and emission lines as probes of star formation (SF) and active galactic nucleus (AGN) activity in a sample of 100 "normal" and local (z ∼ 0.1) emission-line galaxies. The MIR spectra were obtained with the Spitzer Space Telescope Infrared Spectrograph as part of the Spitzer-SDSS-GALEX Spectroscopic Survey, which includes multiwavelength photometry from the ultraviolet to the far-infrared and optical spectroscopy. The continuum and features were extracted using PAHFIT, a decomposition code which we find to yield PAH equivalent widths (EWs) up to ∼30 times larger than the commonly used spline methods. Despite the lack of extreme objects in our sample (such as strong AGNs, low-metallicity galaxies, or ULIRGs), we find significant variations in PAH, continuum, and emission-line properties, and systematic trends between these MIR properties and optically derived physical properties, such as age, metallicity, and radiation field hardness. We revisit the diagnostic diagram relating PAH EWs and [Ne ii]12.8 μm/[O iv]25.9 μm line ratios and find it to be in much better agreement with the standard optical SF/AGN classification than when spline decompositions are used, while also potentially revealing obscured AGNs. The luminosity of individual PAH components, of the continuum, and, with poorer statistics, of the neon emission lines and molecular hydrogen lines are found to be tightly correlated to the total infrared (TIR) luminosity, making individual MIR components good gauges of the total dust emission in SF galaxies. Like the TIR luminosity, these individual components can be used to estimate dust attenuation in the UV and in Hα lines based on energy balance arguments. We also propose average scaling relations between these components and dust-corrected, Hα-derived SF rates.

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“…At 8 μm, most of the emission originates in strong features of PAH molecules, which are considered to be good tracers of warm UV-irradiated photodissociation regions (PDR; Hollenbach & Tielens 1997). Since these complex molecules are destroyed inside the ionized gas of an Hii region (Cesarsky et al 1996;Povich et al 2007;Lebouteiller et al 2007), they indicate the limits of the ionization front and delineate the boundaries of the bubble nebula. The 870 μm emission follows the 8 μm emission distribution, which is bright in the western and southern regions of Gum 31.…”

Section: μM Emission and Comparison With Other Wavelengthsmentioning

confidence: 99%

870μm continuum observations of the bubble-shaped nebula Gum 31

Duronea

Vasquez

Gómez

et al. 2015

A&A

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Aims. We present here a study of the cold dust in the close environs of the ring nebula Gum 31. We aim at deriving the physical properties of the molecular gas and dust associated with the nebula, and investigating its correlation with the star formation in the region, which was probably triggered by the expansion of the ionization front against its environment. Methods. We make use of 870 μm emission data obtained with the Large APEX Bolometer Camera (LABOCA) to map the dust emission. The 870 μm emission provides an excellent probe of mass and density of dense molecular clouds. The obtained LABOCA image was compared to archival infrared, radio continuum, and optical images. Results. The 870 μm emission follows the 8 μm (Spitzer), 250 μm, and 500 μm (Herschel) emission distributions showing the classical morphology of a two-dimensional projection of a spherical shell. We use the 870 μm and 250 μm images to identify 60 dust clumps in the collected layers of molecular gas using the Gaussclumps algorithm. The clumps have effective deconvolved radii between 0.16 pc and 1.35 pc, masses between 70 M and 2800 M , and volume densities between 1.1 × 10 3 cm −3 and ∼2.04× 10 5 cm −3 . The total mass of the clumps is ∼37 600 M . The dust temperature of the clumps is in the range from 21 K to 32 K, while inside the Hii region it reaches ∼40 K. The clump mass distribution for the sample is fitted by a power law dN/dlog(M/M ) ∝ M −α , with α = 0.93± 0.28. The slope differs from those obtained for the stellar IMF in the solar neighborhood, suggesting that the clumps are not direct progenitors of single stars/protostars. The mass-radius relationship for the 41 clumps detected in the 870 μm emission shows that only 37% of them lie in or above the high-mass star formation threshold. Most of this 37% have candidate YSOs projected inside their limits. A comparison of the dynamical age of the Hii region with the fragmentation time, allowed us to conclude that the collect-and-collapse mechanism may be important for the star formation at the edge of Gum 31, although other processes may be acting simultaneously. The position of the identified young stellar objects in the region is also a strong indicator that the collect-and-collapse process is acting.

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A Multiwavelength Study of M17: The Spectral Energy Distribution and PAH Emission Morphology of a Massive Star Formation Region

Cited by 177 publications

References 44 publications

Tracing the energetics and evolution of dust withSpitzer: a chapter in the history of the Eagle Nebula

Tracing the energetics and evolution of dust withSpitzer: a chapter in the history of the Eagle Nebula

Mid-Infrared Spectral Indicators of Star Formation and Active Galactic Nucleus Activity in Normal Galaxies

870μm continuum observations of the bubble-shaped nebula Gum 31

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