Modelling clumpy photon-dominated regions in 3D

Andree-Labsch, Silke; Ossenkopf-Okada, Volker; Röllig, M.

doi:10.1051/0004-6361/201424287

Cited by 46 publications

(70 citation statements)

References 67 publications

(78 reference statements)

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“…Williams & Best, 2014), but is also used by the star formation/ISM community. For example, the Orion Bar PDR (Pellegrini et al, 2009;Andree-Labsch et al, 2017), Sgr B2 (Lis & Goldsmith, 1990;Schmiedeke et al, 2016) and Taurus Molecular Cloud 1 (TMC-1; see e.g. Gratier et al 2016) are just a few targets that have been the subject of bespoke modelling.…”

Section: Why Synthetic Observations?mentioning

confidence: 99%

Synthetic observations of star formation and the interstellar medium

Haworth

Glover

Koepferl

et al. 2018

New Astronomy Reviews

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Synthetic observations are playing an increasingly important role across astrophysics, both for interpreting real observations and also for making meaningful predictions from models. In this review, we provide an overview of methods and tools used for generating, manipulating and analysing synthetic observations and their application to problems involving star formation and the interstellar medium. We also discuss some possible directions for future research using synthetic observations.

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Section: Why Synthetic Observations?mentioning

confidence: 99%

Synthetic observations of star formation and the interstellar medium

Haworth

Glover

Koepferl

et al. 2018

New Astronomy Reviews

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“…4.1 within a factor ∼ 1.25. Hogerheijde et al (1995); Walmsley et al (2000) and Andree-Labsch et al (2017) described the geometry of the Orion bar where the trapezium stars illuminate the PDR, which changes from a face-on to an edge-on orientation along the varying length of the line of sight. This geometry explains the [C I] peak which is symmetric around the peak of the CO emission (Tauber et al 1994).…”

Section: Comparison With the Pdr Of The Orion Barmentioning

confidence: 99%

Unveiling the remarkable photodissociation region of Messier 8

Tiwari

Menten

Wyrowski

et al. 2018

A&A

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Aims. Messier 8 is one of the brightest HII regions in the sky. We collected an extensive dataset comprising multiple submillimeter spectral lines from neutral and ionized carbon and from CO. Based on it, we aim to understand M8's morphology and that of its associated photo dissociation region and to carry out a quantitative analysis of the regions' physical conditions such as kinetic temperatures and volume densities. Methods. Using the Stratospheric Observatory For Infrared Astronomy (SOFIA), the Atacama Pathfinder Experiment (APEX) 12 m and the Institut de Radioastronomie Millimétrique (IRAM) 30 m telescopes, we have performed a comprehensive imaging survey of the emission from the fine structure lines of [C II] and [C I] and multiple rotational transitions of carbon monoxide (CO) isotopologues within 1.3 × 1.3 pc around the dominant Herschel 36 (Her 36) system composed of at least three massive stars. To further explore the morphology of the region we compare archival infrared, optical and radio images of the nebula with our newly obtained fine structure line and CO data, in particular with the velocity information they provide. We perform a quantitative analysis, using both LTE and non-LTE methods to determine the abundances of some of the observed species as well as kinetic temperatures and volume densities. Results. Bright CO, [C II] and [C I] emission has been found towards the HII region and the photodissociation region (PDR) in M8. Our analysis places the bulk of the molecular material in the background of the nebulosity illuminated by the bright stellar systems Her 36 and 9 Sagitarii. Since the emission from all observed atomic and molecular tracers peaks at or close to the position of Her 36, we conclude that the star is still physically close to its natal dense cloud core and heats it. A veil of warm gas moves away from Her 36 toward the Sun and its associated dust contributes to the foreground extinction in the region. One of the most prominent star forming regions in M8, the Hourglass Nebula, is particularly bright due to cracks in this veil close to Her 36. By using radiative transfer modeling of different transitions of CO isotopologues, we obtain H 2 densities ranging from ∼ 10 4 -10 6 cm -3 and kinetic temperatures of 100 -150 K in the bright PDR caused by Her 36.

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“…These different results may be somehow related to the non-uniform matter distribution within the Orion Bar. Goicoechea et al (2016) and Andree-Labsch et al (2017) demonstrate a clumpiness of the Orion Bar. So, some disagreement between our results and the observed picture can be caused by the fine structure of the PDR unresolved in our model.…”

Section: Discussionmentioning

confidence: 96%

“…In other words, we only consider the PDR, but not the ionized region. We calculated the 'M42 inner' radiation field at a distance of 0.22 parsec, which corresponds to the projected distance 111 ′′ from the main ionizing star to the Bar according to Pellegrini et al (2009) andAndree-Labsch et al (2017), and then passed the radiation field to the described above plane-parallel modification of the MARION code. The intensity of the radiation field is χ = 4.4 · 10 4 in units of the Draine field (Draine (1979) Dust-gas interaction Tielens (2005) 1978) in the wavelength range of 91.2 < λ ≤ 200 nm.…”

Section: Model Calculationmentioning

confidence: 99%

Merged H/H2 and C+/C/CO transitions in the Orion Bar

Kirsanova

Wiebe

2019

Monthly Notices of the Royal Astronomical Society

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High-resolution ALMA images towards the Orion Bar show no discernible offset between the peak of H 2 emission in the photodissociation region (PDR) and the 13 CO(3-2) and HCO + (4-3) emission in the molecular region. This implies that positions of H 2 and CO dissociation fronts are indistinguishable in the limit of ALMA resolution. We use the chemo-dynamical model MARION to show that the ALMA view of the Orion Bar, namely, no appreciable offset between the 13 CO(3-2) and HCO + (4-3) peaks, merged H 2 and CO dissociation fronts, and high intensity of HCO + (4-3) emission, can only be explained by the ongoing propagation of the dissociation fronts through the molecular cloud, coupled to the dust motion driven by the stellar radiation pressure, and are not reproduced in the model where the dissociation fronts are assumed to be stationary. Modelling line intensities, we demonstrate that after the fronts have merged, the angular separation of the 13 CO(3-2) and HCO + (4-3) peaks is indeed unresolvable with the ALMA observations. Our model predictions are consistent with the results of the ALMA observations about the relation of the bright HCO + (4-3) emission to the compressed gas at the border of the PDR in the sense that the theoretical HCO + (4-3) peak does correspond to the gas density enhancement, which naturally appears in the dynamical simulation, and is located near the H 2 dissociation front at the illuminated side of the CO dissociation front.

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Modelling clumpy photon-dominated regions in 3D

Cited by 46 publications

References 67 publications

Synthetic observations of star formation and the interstellar medium

Synthetic observations of star formation and the interstellar medium

Unveiling the remarkable photodissociation region of Messier 8

Merged H/H2 and C+/C/CO transitions in the Orion Bar

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