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

被引：39

作者：

Andree-Labsch, S. ^{[1
]}

Ossenkopf-Okada, V. ^{[1
]}

Roellig, M. ^{[1
]}

机构：

[1] Univ Cologne, Inst Phys, Zulpicher Str 77, D-50937 Cologne, Germany

来源：

ASTRONOMY & ASTROPHYSICS | 2017年 / 598卷

关键词：

photon-dominated region; ISM: structure; ISM: clouds; submillimeter: ISM; infrared: ISM; radiative transfer; PHOTODISSOCIATION REGIONS; MOLECULAR CLOUDS; INTERSTELLAR-MEDIUM; M17; SW; C-II; SUBMILLIMETER OBSERVATIONS; CHEMICAL STRATIFICATION; COLOGNE DATABASE; LINE EMISSION; MASS-SPECTRA;

D O I：

10.1051/0004-6361/201424287

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

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-tau 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-iota 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] 158 mu m and different (CO)-C-12/13 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.

引用

页数：32

共 91 条

[1]

ALVES JF, 2002, ORIGIN STARS PLANETS

[2] Evolution of dust in the Orion Bar with Herschel I. Radiative transfer modelling [J].

Arab, H. ;

Abergel, A. ;

Habart, E. ;

Bernard-Salas, J. ;

Ayasso, H. ;

Dassas, K. ;

Martin, P. G. ;

White, G. J. .

ASTRONOMY & ASTROPHYSICS, 2012, 541

[3]

Asplund M, 2005, ASTR SOC P, V336, P25

[4] Herschel observations of EXtra-Ordinary Sources (HEXOS): The present and future of spectral surveys with Herschel/ HIFI [J].

Bergin, E. A. ;

Phillips, T. G. ;

Comito, C. ;

Crockett, N. R. ;

Lis, D. C. ;

Schilke, P. ;

Wang, S. ;

Bell, T. A. ;

Blake, G. A. ;

Bumble, B. ;

Caux, E. ;

Cabrit, S. ;

Ceccarelli, C. ;

Cernicharo, J. ;

Daniel, F. ;

de Graauw, Th. ;

Dubernet, M. -L. ;

Emprechtinger, M. ;

Encrenaz, P. ;

Falgarone, E. ;

Gerin, M. ;

Giesen, T. F. ;

Goicoechea, J. R. ;

Goldsmith, P. F. ;

Gupta, H. ;

Hartogh, P. ;

Helmich, F. P. ;

Herbst, E. ;

Joblin, C. ;

Johnstone, D. ;

Kawamura, J. H. ;

Langer, W. D. ;

Latter, W. B. ;

Lord, S. D. ;

Maret, S. ;

Martin, P. G. ;

Melnick, G. J. ;

Menten, K. M. ;

Morris, P. ;

Mueller, H. S. P. ;

Murphy, J. A. ;

Neufeld, D. A. ;

Ossenkopf, V. ;

Pagani, L. ;

Pearson, J. C. ;

Perault, M. ;

Plume, R. ;

Roelfsema, P. ;

Qin, S. -L. ;

Salez, M. .

ASTRONOMY & ASTROPHYSICS, 2010, 521

[5] Spatial variation of the cooling lines in the Orion Bar from Herschel/PACS [J].

Bernard-Salas, J. ;

Habart, E. ;

Arab, H. ;

Abergel, A. ;

Dartois, E. ;

Martin, P. ;

Bontemps, S. ;

Joblin, C. ;

White, G. J. ;

Bernard, J. -P. ;

Naylor, D. .

ASTRONOMY & ASTROPHYSICS, 2012, 538

[6] 3d-pdr: a new three-dimensional astrochemistry code for treating photodissociation regions [J].

Bisbas, T. G. ;

Bell, T. A. ;

Viti, S. ;

Yates, J. ;

Barlow, M. J. .

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 2012, 427 (03) :2100-2118

[7] LINE EMISSION FROM CLUMPY PHOTODISSOCIATION REGIONS [J].

BURTON, MG ;

HOLLENBACH, DJ ;

TIELENS, AGGM .

ASTROPHYSICAL JOURNAL, 1990, 365 (02) :620-639

[8] A non-equilibrium ortho-to-para ratio of water in the Orion PDR [J].

Choi, Y. ;

van der Tak, F. F. S. ;

Bergin, E. A. ;

Plume, R. .

ASTRONOMY & ASTROPHYSICS, 2014, 572

[9] The chemistry and spatial distribution of small hydrocarbons in UV-irradiated molecular clouds: the Orion Bar PDR [J].

Cuadrado, S. ;

Goicoechea, J. R. ;

Pilleri, P. ;

Cernicharo, J. ;

Fuente, A. ;

Joblin, C. .

ASTRONOMY & ASTROPHYSICS, 2015, 575

[10] A clumpy-cloud photon-dominated regions model of the global far-infrared line emission of the Milky Way [J].

Cubick, M. ;

Stutzki, J. ;

Ossenkopf, V. ;

Kramer, C. ;

Roellig, M. .

ASTRONOMY & ASTROPHYSICS, 2008, 488 (02) :623-634

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