CO and H2O vibrational emission toward Orion Peak 1 and Peak 2

Details CO and H2O vibrational emission toward Orion Peak 1 and Peak 2 CO and H2O vibrational emission toward Orion Peak 1 and Peak 2

May 2002

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002a%26a...386.1074g&link_type=abstract

Astronomy and Astrophysics, v.386, p.1074-1102 (2002)

Astronomy and Astrophysics

Astrophysics

24

Shock Waves, Ism: Abundances, Ism: Individual Objects: Orion

Scientific paper

ISO/SWS observations of Orion Peak 1 and Peak 2 show strong emission in the ro-vibrational lines of CO v=1-0 at 4.45-4.95 μm and of H2O ν2=1-0 at 6.3-7.0 μm. Toward Peak 1 the total flux in both bands is, assuming isotropic emission, ≈2.4 and ≈0.53 Lsun, respectively. This corresponds to ≈14 and ≈3% of the total H2 luminosity in the same beam. Two temperature components are found to contribute to the CO emission from Peak 1/2: a warm component, with TK=200-400 K, and a hot component with Tk~3×103 K. At Peak 2 the CO flux from the warm component is similar to that observed at Peak 1, but the hot component is a factor of ≈2 weaker. The H2O band is ≈25% stronger toward Peak 2, and seems to arise only in the warm component. The P-branch emission of both bands from the warm component is significantly stronger than the R-branch, indicating that the line emission is optically thick. Neither thermal collisions with H2 nor with H I seem capable of explaining the strong emission from the warm component. Although the emission arises in the postshock gas, radiation from the most prominent mid-infrared sources in Orion BN/KL is most likely pumping the excited vibrational states of CO and H2O. CO column densities along the line of sight of N{(CO)}=5-10×1018 cm-2 are required to explain the band shape, the flux, and the P-R-asymmetry, and beam-filling is invoked to reconcile this high N(CO) with the upper limit inferred from the H2 emission. CO is more abundant than H2O by a factor of at least 2. The density of the warm component is estimated from the H2O emission to be ~ 2×107 cm-3. The CO emission from the hot component is neither satisfactorily explained in terms of non-thermal (streaming) collisions, nor by resonant scattering. Vibrational excitation through collisions with H2 for densities of ~3×108 cm-3 or, alternatively, with atomic hydrogen, with a density of at least 107 cm-3, are invoked to explain simultaneously the emission from the hot component and that from the high excitation H2 lines in the same beam. A jump shock is most probably responsible for this emission. The emission from the warm component could in principle be explained in terms of a C-shock. The underabundance of H2O relative to CO could be the consequence of H2O photodissociation, but may also indicate some contribution from a jump shock to the CO warm emission.

Affiliated with

Also associated with

No associations

Rating

CO and H2O vibrational emission toward Orion Peak 1 and Peak 2 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with CO and H2O vibrational emission toward Orion Peak 1 and Peak 2, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and CO and H2O vibrational emission toward Orion Peak 1 and Peak 2 will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1716843