scholarly journals Rotational Fine Structure Lines of Interstellar C2 Toward ζ Persei

1980 ◽  
Vol 87 ◽  
pp. 263-267
Author(s):  
Frederic H. Chaffee ◽  
Barry L. Lutz ◽  
John H. Black ◽  
Paul A. Vanden Bout ◽  
Ronald L. Snell
Keyword(s):  
Fine Structure ◽  
Thermal Equilibrium ◽  
Column Density ◽  
Rotational Temperature ◽  
Detailed Model ◽  
Data Yield ◽  
Fine Structure Lines

We have detected 9 of the rotational fine structure lines of the 2-0 Phillips band of interstellar C2 toward ζ Persei using the Tull spectrograph and Reticon detector on the 2.7 m telescope at the McDonald Observatory. These data yield a total C2 column density of 1.2 × 1013 cm-2 and a rotational temperature of 97 K compared to 1.4 × 1013 cm-2 and 45 K predicted by the detailed model of the cloud by Black, Hartquist and Dalgarno. We suggest that radiative pumping through the Mulliken and Phillips systems has modified the C2 level populations in such a way as to produce an observed rotational temperature which exceeds that arising in pure thermal equilibrium.

scholarly journals Observations of Infrared Fine-Structure Lines: [S III]

1978 ◽  
Vol 76 ◽  
pp. 126-126
Author(s):  
Lawrence T. Greenberg
Keyword(s):  
Fine Structure ◽  
Electron Density ◽  
Experimental Error ◽  
Column Density ◽  
Surface Brightness ◽  
Ngc 7027 ◽  
Structure Line ◽  
Electron Density And Temperature ◽  
Fine Structure Lines

Recent observations of the 18.7 ym fine-structure line of S++ in NGC 7027 and BD+30°3639 (Greenberg, Dyal and Geballe, 1977 Ap.J.(Letters), 213, L74) allow the first determination of an ionic column density in ionized nebulae. The line ratios 18.7 μm/A9532 and λ6312/λ9532, besides yielding both electron density and temperature in the S++ region, have been used to indicate that the fine-structure levels of S++ are collisionally saturated. In this case the 18.7 ym surface brightness directly measures the column density of S++ ions with little dependence upon nebular structure, the major uncertainty being the experimental error. This research has been partially supported by NASA Grants NGR 05-003-511 and NGL 05-003-272.

scholarly journals AGN Spectra as Seen by the Infrared Space Observatory: First Results

1997 ◽  
Vol 159 ◽  
pp. 333-336
Author(s):  
D. Lutz ◽  
R. Genzel ◽  
E. Sturm ◽  
A.F.M. Moorwood ◽  
E. Oliva ◽  
...  
Keyword(s):  
Fine Structure ◽  
Short Wavelength ◽  
Molecular Hydrogen ◽  
Molecular Gas ◽  
Space Observatory ◽  
Infrared Space Observatory ◽  
First Results ◽  
External Galaxies ◽  
First Time ◽  
Fine Structure Lines

AbstractWe discuss 2.5–45 µm spectra of the Circinus galaxy and of Cen A, obtained with the Short Wavelength Spectrometer (SWS) on board the Infrared Space Observatory. The large number of detected ionic fine structure lines, observable also in visually obscured sources, provides strong constraints on the shape of the ionizing spectrum, which is found to exhibit a UV bump peaking at ~ 70 eV in the case of Circinus. Pure rotational emission of molecular hydrogen, directly probing warm molecular gas, can for the first time be detected in external galaxies.

scholarly journals Fine Structure and Dynamics of the Inner Corona

1977 ◽  
Vol 43 ◽  
pp. 9-9
Author(s):  
G.E. Brueckner ◽  
J.D.F. Bartoe ◽  
M.E. VanHoosier
Keyword(s):  
Solar Wind ◽  
Fine Structure ◽  
Thermal Energy ◽  
Column Density ◽  
Line Profiles ◽  
Quiet Sun ◽  
Structure And Dynamics ◽  
Fine Structures ◽  
The Doppler Effect ◽  
Average Size

High spectral (0,05 Å) and spatial (⋍ 1000 km) resolution spectra of the Fe XII line 1349.4 Å reveal the existence of coronal fine structures in the quiet sun against the solar disk. These coronal bright elements have an average size of 2000-3000 km; their column density can be 3 x 1017 cm –2 . In the quiet sun, outward streaming velocities of 10-15 km sec –1 can be measured by means of the Doppler effect. The total kinetic and thermal energy of the outstreaming gas can be estimated to be larger than 1 x 10 5 ergs cm –2 sec –1, enough to account for the heating of the corona and the losses of the solar wind. At the outer limb (cos θ ⋍0.1) line profiles show a strong blue asymmetry, which could be caused by expanding material in a piston-driven shock, whereby the opaque, cool piston causes the asymmetry of the line profile.

Internal rotation of a light symmetric top relative to a heavy planar framework: theoretical calculations of vibration/internal-rotation spectra including effects of rotational barriers and non-degeneracy of perpendicular symmetric top vibrations

1969 ◽  
Vol 313 (1513) ◽  
pp. 149-167 ◽  
Keyword(s):  
Fine Structure ◽  
Internal Rotation ◽  
Theoretical Calculations ◽  
Site Symmetry ◽  
Frequency Range ◽  
Electronic Effects ◽  
Angular Variation ◽  
Band Contour ◽  
Lower Site ◽  
Fine Structure Lines

Model theoretical calculations have been made of the fine structure associated with the perpendicular vibrations of a ‘light’ symmetric top group (such as CH 3 , SiH 3 , etc.) resulting from its internal rotation with respect to an infinitely heavy planar framework. Investigations have been made of the effects on the internal rotational fine structure of the removal of the degeneracy of the perpendicular vibrations as required by the lower site symmetry. Separate calculations have been made for the cases where the removal of degeneracy is caused ( a ) by electronic effects which result in an angular variation of the appropriate force constant, or ( b ) by interaction with another vibration in the framework part of the molecule. It is found that no fine structure lines occur between the non-degenerate frequencies, but that the effect of internal rotation is to generate rotational wings outside this frequency range. The effects of a finite sixfold barrier to internal rotation on the vibrational/internal-rotational absorption band have been calculated for the degenerate and non-degenerate cases. It is shown that certain lines are split by amounts comparable to the barrier height, V 6 , which should therefore be experimentally obtainable from this type of spectrum in favourable cases. The effect of an increasing barrier is to cause more of the intensity within the overall band contour to occur in the vicinity of the vibrational frequency or frequencies, and less in the internal rotational wings, as expected on physical grounds.

scholarly journals Precise Measurements of CH Maser Emission and Its Abundance in Translucent Clouds

2021 ◽  
Vol 257 (2) ◽  
pp. 47
Author(s):  
Ningyu Tang ◽  
Di Li ◽  
Gan Luo ◽  
Carl Heiles ◽  
Sheng-Li Qin ◽  
...  
Keyword(s):  
Thermal Equilibrium ◽  
Column Density ◽  
High Sensitivity ◽  
Local Thermal Equilibrium ◽  
Molecular Gas ◽  
Excitation Temperature ◽  
Hyperfine Transitions ◽  
Visible Wavelengths ◽  
Log Normal ◽  
Log Normal Distribution

Abstract We present high-sensitivity CH 9 cm ON/OFF observations toward 18 extragalactic continuum sources that have been detected with OH 18 cm absorption in the Millennium survey with the Arecibo telescope. CH emission was detected toward 6 of the 18 sources. The excitation temperature of CH has been derived directly through analyzing all detected ON and OFF velocity components. The excitation temperature of CH 3335 MHz transition ranges from −54.5 to −0.4 K and roughly follows a log-normal distribution peaking within [−5, 0] K, which implies overestimation by 20% to more than 10 times during calculating CH column density by assuming the conventional value of −60 or −10 K. Furthermore, the column density of CH would be underestimated by a factor of 1.32 ± 0.03 when adopting local thermal equilibrium assumption instead of using the CH three hyperfine transitions. We found a correlation between the column density of CH and OH following log N(CH) = (1.80 ± 0.49) and log N(OH −11.59 ± 6.87. The linear correlation between the column density of CH and H2 is consistent with that derived from visible wavelengths studies, confirming that CH is one of the best tracers of H2 components in diffuse molecular gas.

scholarly journals Discovery of allenyl acetylene, H2CCCHCCH, in TMC-1

2021 ◽  
Vol 647 ◽  
pp. L3 ◽  
Author(s):  
J. Cernicharo ◽  
C. Cabezas ◽  
M. Agúndez ◽  
B. Tercero ◽  
N. Marcelino ◽  
...  
Keyword(s):  
Column Density ◽  
State Of The Art ◽  
Rotational Temperature ◽  
Signal To Noise Ratio ◽  
Laboratory Data ◽  
The Other ◽  
Signal To Noise ◽  
Chemical Models ◽  
Upper Limit

We present the discovery in TMC-1 of allenyl acetylene, H2CCCHCCH, through the observation of nineteen lines with a signal-to-noise ratio ∼4–15. For this species, we derived a rotational temperature of 7 ± 1 K and a column density of 1.2 ± 0.2 × 1013 cm−2. The other well known isomer of this molecule, methyl diacetylene (CH3C4H), has also been observed and we derived a similar rotational temperature, Tr = 7.0 ± 0.3 K, and a column density for its two states (A and E) of 6.5 ± 0.3 × 1012 cm−2. Hence, allenyl acetylene and methyl diacetylene have a similar abundance. Remarkably, their abundances are close to that of vinyl acetylene (CH2CHCCH). We also searched for the other isomer of C5H4, HCCCH2CCH (1.4-Pentadiyne), but only a 3σ upper limit of 2.5 × 1012 cm−2 to the column density can be established. These results have been compared to state-of-the-art chemical models for TMC-1, indicating the important role of these hydrocarbons in its chemistry. The rotational parameters of allenyl acetylene have been improved by fitting the existing laboratory data together with the frequencies of the transitions observed in TMC-1.

Fine Structure Lines in HII Regions Interacting with Molecular Clouds

1982 ◽  
pp. 73-80 ◽  
Author(s):  
D. A. Naylor ◽  
R. Emery ◽  
B. Fitton ◽  
I. Furniss ◽  
R. E. Jennings ◽  
...  
Keyword(s):  
Fine Structure ◽  
Molecular Clouds ◽  
Hii Regions ◽  
Fine Structure Lines

scholarly journals 30 Doradus as a Nearby Infrared Guide to Starbursts

1999 ◽  
Vol 190 ◽  
pp. 247-248 ◽  
Author(s):  
M. D. Thornley ◽  
N.M. Förster Schreiber ◽  
H.W.W. Spoon ◽  
R. Genzel ◽  
D. Lutz ◽  
...  
Keyword(s):  
Fine Structure ◽  
Short Wavelength ◽  
Massive Stars ◽  
Stellar Populations ◽  
Starburst Galaxies ◽  
Fine Structure Lines ◽  
30 Doradus

We are exploring the properties of obscured starburst galaxies, using observations of atomic fine structure lines taken with the Short Wavelength Spectrometer aboard ISO. However, it is important to ascertain how well our starburst models can recover the properties of the stellar populations in more distant starbursts. For this purpose, we use observations of a nebular “shell” in the 30 Doradus region, to show that our models reliably predict the presence of the very massive stars observed directly in the 30 Doradus region.

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