Journal of The Korean Astronomical Society (천문학회지)

The Korean Astronomical Society (한국천문학회)
권호 표지
DOI QR코드

DOI QR Code

ONE-DIMENSIONAL TREATMENT OF MOLECULAR LINE RADIATIVE TRANSFER IN CLUMPY CLOUDS

  • Park, Yong-Sun (Department of Physics and Astronomy, Seoul National University)
  • Received : 2021.09.29
  • Accepted : 2021.11.22
  • Published : 2021.12.31
Download PDF
⟨ Previous Next ⟩

Abstract

We have revisited Monte Carlo radiative transfer calculations for clumpy molecular clouds. Instead of introducing a three-dimensional geometry to implement clumpy structure, we have made use of its stochastic properties in a one-dimensional geometry. Taking into account the reduction of spontaneous emission and optical depth due to clumpiness, we have derived the excitation conditions of clumpy clouds and compared them with those of three-dimensional calculations. We found that the proposed approach reproduces the excitation conditions in a way compatible to those from three-dimensional models, and reveals the dependencies of the excitation conditions on the size of clumps. When bulk motions are involved, the applicability of the approach is rather vague, but the one-dimensional approach can be an excellent proxy for more rigorous three-dimensional calculations.

Keywords

References

  1. Asensio Ramos, A., & Elitzur, M. 2018, MOLPOP-CEP: An Exact, Fast Code for Multi-level Systems, A&A, 616, A131 https://doi.org/10.1051/0004-6361/201731943
  2. Bernes, C. 1978, A Program for Solving Non-LTE, Radiative Transfer Problems with the Monte Carlo Method, Stockholms Obs. Rep. 15
  3. Bernes, C. 1979, A Monte Carlo Approach to Non-LTE Radiative Transfer Problems, A&A, 73, 67
  4. Blitz, L., & Stark, A. A. 1986, Detection of Clump and Interclump Gas in the Rosette Molecule Cloud Complex, ApJL, 300, L89 https://doi.org/10.1086/184609
  5. Brinch, C., & Hogerheijde, M. R. 2010, LIME - A Flexible, Non-LTE Line Excitation and Radiation Transfer Method for Millimeter and Far-infrared Wavelengths, A&A, 523, 25
  6. Goldreich, P., & Kwan, J. 1974, Molecular Clouds, ApJ, 189, 441 https://doi.org/10.1086/152821
  7. Hennebelle, P., & Falgarone, E. 2012, Turbulent Molecular Clouds, A&ARv, 20, 55 https://doi.org/10.1007/s00159-012-0055-y
  8. Hogerheijde, M. R., & van der Tak, F. F. S. 2000, An Accelerated Monte Carlo Method to Solve Two-dimensional Radiative Transfer and Molecular Excitation. With Applications to Axisymmetric Models of Star Formation, A&A, 362, 697
  9. Juvela, M., 1998 Clumpy Cloud Models for CS and C34S Spectra Observed Towards Southern Massive Star Forming Cores, A&A, 329, 659
  10. Juvela, M., & Padoan, P. 2005, Multiresolution Radiative Transfer for Line Emission, ApJ, 618, 744 https://doi.org/10.1086/426112
  11. Leung, C. M., & Liszt, H. S. 1976, Radiation Transport and Non-LTE Analysis of Interstellar Molecular Lines. I. Carbon Monoxide., ApJ, 208, 732 https://doi.org/10.1086/154657
  12. Molaro, M., Khatri, R., & Sunyaev, R. A. 2016, Probing the Clumping Structure of Giant Molecular Clouds through the Spectrum, Polarisation and Morphology of X-ray Reflection Nebulae, A&A, 589, 88
  13. Moore, E. M., & Marscher, A. P. 1995, Observational Probes of the Small-scale Structure of Molecular Clouds, ApJ, 452, 671 https://doi.org/10.1086/176338
  14. Park, Y.-S., & Hong, S. S. 1995, Excitation and Line Profiles of CO Molecules in Clumpy Interstellar Clouds, A&A, 300, 890
  15. Quenard, D. Bottinelli, S., & Caux, E. 2017, Modelling the 3D Physical Structure of Astrophysical Sources with GASS, MNRAS, 468, 685 https://doi.org/10.1093/mnras/stx404
  16. Rybarczyk, D. R., Stanimirovic, S., Zweibel, E. G., et al. 2020, Small-scale Structure Traced by Neutral Hydrogen Absorption in the Direction of Multiple-component Radio Continuum Sources, ApJ, 893, 152 https://doi.org/10.3847/1538-4357/ab83f7
  17. van der Tak, F. F. S., Black, J. H., Schoier, F. L., et al. 2007, A Computer Program for Fast Non-LTE Analysis of Interstellar Line Spectra. With Diagnostic Plots to Interpret Observed Line Intensity Ratios, A&A, 468, 627 https://doi.org/10.1051/0004-6361:20066820
  18. Yang, B., Stancil, P. C., Balakrishnan, N., & Forrey, R. C. 2010, Rotational Quenching of CO Due to H2 Collisions, ApJ, 718, 1062 https://doi.org/10.1088/0004-637X/718/2/1062