Detection of (Si II) (34. 8 micron) emission in Orion-KL: A measurement of the silicon abundance in dense interstellar gas

Journal Article · Sat Feb 15 04:00:00 EST 1986 · Astrophys. J., Lett. Ed.; (United States)

DOI:https://doi.org/10.1086/184623· OSTI ID:5961726

Haas, M R; Hollenbach, D J; Erickson, E F

We report the first detection of the ground-state fine-structure transition of Si/sup +/ at a rest wavelength determined to be 34.815 +- 0.004 ..mu..m. A 6' NW--SE strip scan across the Orion-KL region shows (Si II) emission from both the extended photodissociation region surrounding theta/sup 1/ Ori C and from the shocked gas NW of BN--KL. The inferred gas-phase silicon elemental abundance relative to hydrogen in the dense (approx.10/sup 5/ cm/sup -3/) primarily neutral photodissociation region is approximately 2.6 x 10/sup -6/, a factor of 0.075 times the solar value and 3.4 times greater than in the moderate density (< or approx. =10/sup 3/ cm/sup -3/) cloud toward zeta Oph. The silicon abundance in the shocked gas is approximately solar, indicating that any preexisting grains have been destroyed in the shock wave unless the gas-phase silicon abundance in the preshock gas is nearly solar. The shock-excited (Si II) (34.8 ..mu..m) emission may arise from shocked wind material in the outflow around IRc2, with wind velocities > or approx. =100 km s/sup -1/.

• Research Organization: Mycol, Incorporated, Synnyvale, California
• OSTI ID: 5961726
• Journal Information: Astrophys. J., Lett. Ed.; (United States), Journal Name: Astrophys. J., Lett. Ed.; (United States) Vol. 301:2; ISSN AJLEA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics &amp; Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABUNDANCE
CHEMISTRY
COSMIC GASES
COSMOCHEMISTRY
DISSOCIATION
ELECTROMAGNETIC RADIATION
ELEMENT ABUNDANCE
ELEMENTS
FAR INFRARED RADIATION
FLUIDS
GASES
INFRARED RADIATION
INFRARED SPECTRA
NEBULAE
RADIATIONS
SEMIMETALS
SHOCK WAVES
SILICON
SPECTRA