COBE-FIRAS Observations of Galactic Lines
Fixsen, D. J. · Bennett, C. L. · Mather, J. C.
Original · EN
The COBE Far InfraRed Absolute Spectrophotometer (FIRAS) observations constitute an unbiased survey over the wavelength range from 100 um to 1 cm over 99% of the sky. Improved calibration of the FIRAS instrument and the inclusion of all of the FIRAS data allow an improved signal to noise determination of the spectral lines by a factor of 2 over our previous results. The resolution is low (0.45 cm⁻¹) so only the strongest lines are observable. The CO chain from J=1-0 to J=8-7 is observed towards the Galactic center. The line ratios are roughly consistent with a 40 K excitation temperature. The 157.7 um C II and 205.3 um N II lines are observable over most of the sky. The 370.4 um and 609.1 um lines of C I, and the 121.9 um line of N II are observed in the Galactic plane. The line ratios at the Galactic center are consistent with a density of n₀ 30 cm⁻³ and a UV flux of G₀ 15 uW m⁻² sr⁻¹ (10 Habing units). The 269 um H2O line is observed toward the Galactic center in absorption.
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