scholarly journals The 12C/13C Ratio in Interstellar Dark Clouds

1980 ◽  
Vol 87 ◽  
pp. 411-416
Author(s):  
W.H. Mccutcheon ◽  
R. L. Dickman ◽  
W.L.H. Shuter ◽  
R. S. Roger
Keyword(s):  
Radiative Transfer ◽  
Interstellar Medium ◽  
Stellar Evolution ◽  
Transfer Problem ◽  
Abundance Ratio ◽  
Radiative Transfer Problem ◽  
Dark Clouds ◽  
Non Equilibrium

Since 13C is believed to be produced by non-equilibrium CNO processing in stellar evolution (Truran 1977), measurements of the carbon ratio Rc ≡ [12C] / [13C] in the interstellar medium may provide important information on nucleo-synthesis. Commonly, the ratio (N13/N18)LTE ≡ [13CO/C18O]LTE is measured and from this RLTE ≡ [12CO/13CO]LTE is deduced and these values are often identified with Rc. However, this line of reasoning can be misleading for two reasons (Dickman et al. 1979):(1) The difficulty of determining accurate column densities, [13C16O] and [12C18O], because of the complexity of the radiative transfer problem;(2) The possible role of fractionation, whereby RCO ≡ [12CO] / [13CO] does not necessarily reflect the initial atomic abundance ratio RC (Watson et al. 1976, Langer 1977, Liszt 1978).

scholarly journals Radiative transfer in silylidene molecule

2014 ◽  
pp. 37-44 ◽  
Author(s):  
M. Sharma ◽  
M.K. Sharma ◽  
U.P. Verma ◽  
S. Chandra
Keyword(s):  
Radiative Transfer ◽  
Interstellar Medium ◽  
Transfer Problem ◽  
Microwave Spectrum ◽  
Unsuccessful Attempt ◽  
Radiative Transfer Problem ◽  
Brightness Temperatures ◽  
Radiative Transitions ◽  
Collisional Transitions

In order to search for silylidene (H2CSi) in the interstellar medium, Izuha et al. (1996) recorded microwave spectrum of H2CSi in laboratory and made an unsuccessful attempt of its identification in IRC +10216, Ori KL, Sgr B2, through its 717-616 transition at 222.055 GHz. For finding out if there are other transitions of H2CSi which may help in its identification in the interstellar medium, we have considered 25 rotational levels of ortho-H2CSi connected by collisional transitions and 35 radiative transitions, and solved radiative transfer problem using the LVG approximation. We have found that the brightness temperatures of 919-818, 918-817, 101,10-919, 1019-918, 111,11-101,10, 111,10-1019 and 121,12-111,11 transition are larger than that of 717-616 transition. Thus, these transitions may help in detection of H2CSi in the interstellar medium.

scholarly journals Diffuse Galactic Light in the UV and Visible

1990 ◽  
Vol 139 ◽  
pp. 127-138
Author(s):  
A. N. Witt
Keyword(s):  
Radiative Transfer ◽  
Interstellar Medium ◽  
Transfer Problem ◽  
Coherent Scattering ◽  
Space Mission ◽  
Radiative Transfer Problem ◽  
The Galaxy ◽  
The Subject ◽  
High Degree ◽  
Galactic Distribution

The diffuse galactic light, resulting from the coherent scattering of galactic starlight by dust grains contained in the general interstellar medium, has been the subject of active investigation for nearly 60 years. The separation of the diffuse galactic light from the other sources contributing to the light from the night sky has proven difficult, and different attempts at measuring the intensity and galactic distribution of the diffuse galactic light, both in the visible and the UV, are reviewed here. The interpretation of such measurements in terms of average scattering properties of interstellar grains is subject to additional uncertainties, stemming from the high degree of idealization imposed on the galaxy models used to study the radiative transfer problem. In the visible, the observations are more nearly definitive and the model problems less severe; reasonably consistent scattering properties have therefore been derived for this spectral region. In the UV, the situation is considerably less satisfactory, mainly due to a lack of sufficiently extensive, reliable measurements of the diffuse galactic light intensity at λ < 200 nm. A dedicated space mission may be the required solution. The radiative transfer in the UV presents serious difficulties due to the increasing opacity of the interstellar medium with shorter wavelengths and the resulting growing importance of the local galactic structure.

scholarly journals Discontinuities in numerical radiative transfer

2019 ◽  
Vol 622 ◽  
pp. A162 ◽  
Author(s):  
Gioele Janett
Keyword(s):  
Radiative Transfer ◽  
Transfer Equation ◽  
Radiative Transfer Equation ◽  
Transfer Problem ◽  
Stellar Atmospheres ◽  
Physical Parameters ◽  
Radiative Transfer Problem ◽  
Intermittent Behavior ◽  
High Order Convergence ◽  
Magnetohydrodynamic Simulations

Observations and magnetohydrodynamic simulations of solar and stellar atmospheres reveal an intermittent behavior or steep gradients in physical parameters, such as magnetic field, temperature, and bulk velocities. The numerical solution of the stationary radiative transfer equation is particularly challenging in such situations, because standard numerical methods may perform very inefficiently in the absence of local smoothness. However, a rigorous investigation of the numerical treatment of the radiative transfer equation in discontinuous media is still lacking. The aim of this work is to expose the limitations of standard convergence analyses for this problem and to identify the relevant issues. Moreover, specific numerical tests are performed. These show that discontinuities in the atmospheric physical parameters effectively induce first-order discontinuities in the radiative transfer equation, reducing the accuracy of the solution and thwarting high-order convergence. In addition, a survey of the existing numerical schemes for discontinuous ordinary differential systems and interpolation techniques for discontinuous discrete data is given, evaluating their applicability to the radiative transfer problem.

scholarly journals Comparison of parallel eigensolvers for a discretized radiative transfer problem

PAMM ◽  
2007 ◽  
Vol 7 (1) ◽  
pp. 1022805-1022806 ◽  
Author(s):  
P. B. Vasconcelos ◽  
O. A. Marques
Keyword(s):  
Radiative Transfer ◽  
Transfer Problem ◽  
Radiative Transfer Problem

scholarly journals The 2D continuum radiative transfer problem

2004 ◽  
Vol 417 (3) ◽  
pp. 793-805 ◽  
Author(s):  
I. Pascucci ◽  
S. Wolf ◽  
J. Steinacker ◽  
C. P. Dullemond ◽  
Th. Henning ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Transfer Problem ◽  
Radiative Transfer Problem
Sign in / Sign up

Export Citation Format

Share Document