Millimeter and Submillimeter Emissions from Galactic and Extragalactic Photodissociation Regions |
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| Authors: | Abdul Qaiyum |
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| Institution: | (1) Department of Physics, Aligarh Muslim University, Aligarh, 202002, India |
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| Abstract: | The galactic and Extragalactic photodissociation regions are primarily heated by photoelectrons ejected from the surface of interstellar dust grains by Far-ultraviolet (FUV) photons. But there is no direct mechanism to measure the photoelectric heating efficiency. To understand the role of dust grains in processing the Interstellar Radiation Field (ISRF) and heating the gas, we compare the intensities I
CII, I
CO and I
FIR for (2
P
3/2→2
P
1/2) & (J = 1→ 0) line emission of CII & CO at 158 μm & 2.6 mm and integrated far-infrared from number of photodissociation regions, HII regions, planetary nebulae, reflection nebulae and high latitude translucent clouds (HLCs). It is found that I
CII is linearly correlated with I
FIR. In the cold medium where cloud is exposed to weak radiations temperature is low and most of the cooling is due to CII] emissions. As a result the ratio of I
CII/I
FIR provide indirect method to evaluate the photoelectric heating efficiency. For the neutral cold medium it is evaluated to be ∼0.028. The FUV radiation field G
0 are estimated through the model calculation of I
CII and I
CO for different galactic and photodissociation regions. The intensity of FIR radiation I
FIR are well represented as 1.23×10−4
G
0(ergs cm−2 s−1 sr−1) almost same as estimated for HLCs by Ingalls et al (2002). Hydrogen density for each source has also been estimated. |
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| Keywords: | Photodissociation regions photoelectric heating cooling lines fine structure and rotational transitions FIR radiations dust grains |
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