Evolution of interstellar dust with<i>Herschel</i>. First results in the photodissociation regions of NGC 7023

Abergel, A.; Arab, H.; Compiègne, M.; Kirk, J. M.; Ade, Peter A. R.; Anderson, L. D.; André, P.; Baluteau, J. P.; Bernard, J.-P.; Blagrave, K.; Bontemps, Sylvain; Boulanger, F.; Cohen, Martin; Cox, P.; Dartois, E.; Davis, G. R.; Emery, R. J.; Fulton, T.; Gry, C.; Habart, E.; Huang, M.; Joblin, C.; Jones, Scott C.; Lagache, G.; Lim, T.; Madden, S.; Makiwa, G.; Martín, P. G.; Miville-Deschênes, M.-A.; Molinari, S.; Moseley, H.; Motte, F.; Naylor, David; Okumura, K.; Gonçalves, D. Pinheiro; Polehampton, E. T.; Rodón, J. A.; Russeil, D.; Saraceno, P.; Sauvage, M.; Sidher, S.; Spencer, L. D.; Swinyard, Bruce; Ward-Thompson, Derek; White, G. J.; Zavagno, A.

doi:10.1051/0004-6361/201014643

Cited by 46 publications

(11 citation statements)

References 30 publications

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“…Images from the PACS instrument (Poglitsch et al 2010) on board of the Herschel Space Observatory (Pilbratt et al 2010) at 70 and 160 μm were obtained by Abergel et al (2010) as a part of the "Evolution of interstellar dust" key program and have been presented in Arab et al (2012) Bernard-Salas et al (2012). The spatial resolution of this data changes with thewavelength being 4 5 at 63 μm 10″ at 145 μm and 11″ at 157 μm.…”

Section: Observations and Datamentioning

confidence: 99%

THE ORION H ii REGION AND THE ORION BAR IN THE MID-INFRARED

Salgado

Berné

Adams

et al. 2016

ApJ

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We present mid-infrared photometry of the Orion bar obtained with theFaint Object infraRed Camera for the SOFIA Telescope (FORCAST) onboard SOFIA at 6. 4, 6.6, 7.7, 19.7, 31.5, and 37.1 μm. By complementing this observationwith archival FORCAST and Herschel/PACS images, we are able to construct a complete infrared spectral energy distribution of the Huygens region in the Orion nebula. Comparing the infrared images with gas tracers, we find that PACS maps trace the molecular cloud, while the FORCAST data trace the photodissociation region (PDR) and theH II region. Analysis of the energetics of the region reveal that the PDR extends for 0.28 pc along the lineofsight and that the bar is inclined at an angle of 4°. The infrared and submillimeter images reveal that the Orion bar represents a swept-up shell with a thickness of 0.1 pc. The mass of the shell implies a shock velocity of ;3 km s −1 and an age of ;10 5 years for the H II region. Our analysis shows that the UV and infrared dust opacities in the H II region and the PDR are a factor 5 to 10 lower than in the diffuse interstellar medium. In the ionized gas, Lyα photons are a major source of dust heating at distances larger than ;0.06 pc from θ 1 OriC. Dust temperatures can be explained if the size of the grains is between 0.1 and 1 μm. We derive the photoelectric heating efficiency of the atomic gas in the Orion bar. The results are in good qualitative agreement with models and the quantitative differences indicate a decreased polycyclic aromatic hydrocarbonabundance in this region.

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Section: Observations and Datamentioning

confidence: 99%

THE ORION H ii REGION AND THE ORION BAR IN THE MID-INFRARED

Salgado

Berné

Adams

et al. 2016

ApJ

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“…In this section, we focus on the analysis of dust emission as an independent tracer. Observational data obtained with the Infrared Array Camera (IRAC), Multiband Imaging Photometer (MIPS) (Spitzer), PACS, and SPIRE photometers (SUPREME method is not used but standard data processing with naive gridding method) and IRAM, convolved to the 500 µm beam with a FWHM of 35.1", are used to obtain the physical properties for NGC 7023 NW and E. These data offer a large wavelength range from 3.6 µm to 1.2 mm, covering the entire infrared emission of grains, and are described in Abergel et al (2010). Physical properties within the PDRs are determined using two complementary approaches: modified black body fits and radiative transfer calculations.…”

Section: Physical Properties Derived From Dust Continuum Analysismentioning

confidence: 99%

“…NGC 7023 has been observed in several Herschel programs providing a wealth of spatial and spectral information on gas and dust in the heart of PDRs. Abergel et al (2010) combined Spitzer and Herschel maps to study the spatial variations of the dust properties towards NGC 7023 E. The authors analyse the dust component at thermal equilibrium, which contains most of the dust mass. The results clearly show evidence of changes in dust properties from the diffuse interstellar medium to denser regions.…”

Section: Introductionmentioning

confidence: 99%

Physical structure of the photodissociation regions in NGC 7023

Koehler

Habart

Arab

et al. 2014

A&A

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Context. The determination of the physical conditions in molecular clouds is a key step towards our understanding of their formation and evolution of associated star formation. We investigate the density, temperature, and column density of both dust and gas in the photodissociation regions (PDRs) located at the interface between the atomic and cold molecular gas of the NGC 7023 reflection nebula. We study how young stars affect the gas and dust in their environment. Aims. Several Herschel Space Telescope programs provide a wealth of spatial and spectral information of dust and gas in the heart of PDRs. We focus our study on Spectral and Photometric Image Receiver (SPIRE) Fourier-Transform Spectrometer (FTS) fully sampled maps that allow us for the first time to study the bulk of cool/warm dust and warm molecular gas (CO) together. In particular, we investigate if these populations spatially coincide, if and how the medium is structured, and if strong density and temperature gradients occur, within the limits of the spatial resolution obtained with Herschel. Methods. The SPIRE FTS fully sampled maps at different wavelengths are analysed towards the northwest (NW) and the east (E) PDRs in NGC 7023. We study the spatial and spectral energy distribution of a wealth of intermediate rotational 12 CO 4 ≤ J u ≤ 13 and 13 CO 5 ≤ J u ≤ 10 lines. A radiative transfer code is used to assess the gas kinetic temperature, density, and column density at different positions in the cloud. The dust continuum emission including Spitzer, the Photoconductor Array Camera and Spectrometer (PACS), and SPIRE photometric and the Institute for Radio Astronomy in the Millimeter Range (IRAM) telescope data is also analysed. Using a single modified black body and a radiative transfer model, we derive the dust temperature, density, and column density. Results. The cloud is highly inhomogeneous, containing several irradiated dense structures. Excited 12 CO and 13 CO lines and warm dust grains localised at the edge of the dense structures reveal high column densities of warm/cool dense matter. Both tracers give a good agreement in the local density, column density, and physical extent, leading to the conclusion that they trace the same regions. The derived density profiles show a steep gradient at the cloud edge reaching a maximum gas density of 10 5 −10 6 cm −3 in the PDR NGC 7023 NW and 10 4 −10 5 cm −3 in the PDR NGC 7023 E and a subsequent decrease inside the cloud. Close to the PDR edges, the dust temperature (30 K and 20 K for the NW and E PDRs, respectively) is lower than the gas temperature derived from CO lines (65−130 K and 45−55 K, respectively). Further inside the cloud, the dust and gas temperatures are similar. The derived thermal pressure is about 10 times higher in NGC 7023 NW than in NGC 7023 E. Comparing the physical conditions to the positions of known young stellar object candidates in NGC 7023 NW, we find that protostars seem to be spatially correlated with the dense structures. Conclusions. Our approach combining bo...

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“…Although no far infrared spectral data exist for NGC 7023, Herschel Space Observatory 70, 160, 250 µm data suggest that the dust continuum component has a temperature of 25-30 K and the spectral energy distribution (SED) of the nebula peaks at a wavelength beyond 100 µm (Abergel et al 2010;Berné & Tielens 2012). This means that most of the continuum flux is emitted at wavelengths beyond 20 µm.…”

Section: Aromatic or Mixed?mentioning

confidence: 99%

UNIDENTIFIED INFRARED EMISSION BANDS: PAHs or MAONs?

Kwok

Zhang

2013

ApJ

109

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We suggest that the carrier of the unidentified infrared emission (UIE) bands is an amorphous carbonaceous solid with mixed aromatic/aliphatic structures, rather than free-flying polycyclic aromatic hydrocarbon (PAH) molecules. Through spectral fittings of the astronomical spectra of the UIE bands, we show that a significant amount of the energy is emitted by the aliphatic component, implying that aliphatic groups are an essential part of the chemical structure. Arguments in favor of an amorphous, solid-state structure rather than a gas-phase molecule as a carrier of the UIE are also presented.

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Evolution of interstellar dust withHerschel. First results in the photodissociation regions of NGC 7023

Cited by 46 publications

References 30 publications

THE ORION H ii REGION AND THE ORION BAR IN THE MID-INFRARED

THE ORION H ii REGION AND THE ORION BAR IN THE MID-INFRARED

Physical structure of the photodissociation regions in NGC 7023

UNIDENTIFIED INFRARED EMISSION BANDS: PAHs or MAONs?

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