2017A&A...598A...2A


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.14CEST19:45:28

2017A&A...598A...2A - Astronomy and Astrophysics, volume 598A, 2-2 (2017/2-1)

Modelling clumpy photon-dominated regions in 3D Understanding the Orion Bar stratification.

ANDREE-LABSCH S., OSSENKOPF-OKADA V. and ROLLIG M.

Abstract (from CDS):

Context. Models of photon-dominated regions (PDRs) still fail to fully reproduce some of the observed properties. In particular they do not reproduce the combination of the intensities of different PDR cooling lines together with the chemical stratification, as observed for example for the Orion Bar PDR.
Aims. We aim to construct a numerical PDR model, KOSMA-τ 3D, to simulate full spectral cubes of line emission from arbitrary PDRs in three dimensions (3D). The model will reproduce the intensity of the main cooling lines from the Orion Bar PDR and the observed layered structure of the different transitions.
Methods. We built up a 3D compound, made of voxels (3D pixels) that contain a discrete mass distribution of spherical "clumpy" structures, approximating the fractal ISM. To analyse each individual clump the new code was combined with the KOSMA-τ PDR model. Probabilistic algorithms were used to calculate the local FUV flux for each voxel as well as the voxel-averaged line emissivities and optical depths, based on the properties of the individual clumps. Finally, the computation of the radiative transfer through the compound provided full spectral cubes. To test the new model we tried to simulate the structure of the Orion Bar PDR and compared the results to observations from HIFI/Herschel and from the Caltech Submillimetre Observatory (CSO). In this context new Herschel data from the HEXOS guaranteed-time key program is presented.
Results. Our model is able to reproduce the line-integrated intensities within a factor of 2.5 and the observed stratification pattern within 0.016 pc for the [CII] 158µm and different 12/13CO and HCO+ transitions, based on the representation of the Orion Bar PDR by a clumpy edge-on cavity wall. In the cavity wall, a large fraction of the total mass needs to be contained in clumps. The mass of the interclump medium is constrained by the FUV penetration. Furthermore, the stratification profile cannot be reproduced by a model that has the same amount of clump and interclump mass in each voxel; dense clumps need to be removed from the PDR surface.

Abstract Copyright: © ESO, 2017

Journal keyword(s): photon-dominated region - ISM: structure - ISM: clouds - submillimeter: ISM - infrared: ISM - radiative transfer

Simbad objects: 11

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Number of rows : 11

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 NAME OMC1 Ridge reg 05 35 13.4 -05 23 07           ~ 123 0
2 * tet01 Ori C ** 05 35 16.46375 -05 23 22.8486 4.20 5.15 5.13 4.91 4.73 O7Vp 1272 1
3 NAME Trapezium Cluster As* 05 35 16.5 -05 23 14           ~ 1467 1
4 * tet01 Ori D Y*O 05 35 17.2574309230 -05 23 16.567215876 6.08 6.79 6.70 6.40 6.20 B1.5Vp 306 0
5 M 42 HII 05 35 17.3 -05 23 28           ~ 3724 0
6 NAME Orion Bright Bar reg 05 35 22.30 -05 24 33.0           ~ 716 0
7 NAME Horsehead Nebula DNe 05 40 59.0 -02 27 30           ~ 445 0
8 NAME ORI MOL CLOUD MoC 05 56 -01.8           ~ 848 1
9 NAME Polaris Flare MoC 11 00 14.8 +86 10 52           ~ 162 1
10 NGC 6618 OpC 18 20 47 -16 10.3           ~ 1484 0
11 NGC 7027 PN 21 07 01.8 +42 14 10   9.1 10.9     ~ 2323 1

    Equat.    Gal    SGal    Ecl

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2020.07.14-19:45:28

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