Observation of the diffuse galactic emission at 6.2 μm

Abstract

We present the observation of the 6.2 μm emission of the inner galactic disk obtained with the AROME balloon‐borne experiment. The galactic coordinates of the covered region are −5°≤1≤35° and ‖ b‖≤6°, with an angular resolution of 0.7°. The measurements reveal the existence of an emission feature at 6.2 μm all over this region. The averaged 6.2 μm surface brightness (‖ b ‖≤1°, 8°≤1≤35°) is λIλ=(1.2±0.3) 10−5 Wm−2 sr−1, with a continuum λ Iλ=(5.9±1.2) 10−6 Wm−2 sr−1 and a feature’s intensity Δλ Iλ=(6.1±1.3) 10−7 Wm−2 sr−1. We can compare this value to the 3.3 μm emission observed with AROME (Giard et al. 19881) and to the 12 μm (IRAS) surface brightness: the ratios are respectively Δλ Iλ (6.2/3.3)=9±2 (extinction corrected) and Δλ Iλ 6.2/λ Iλ12=0.09±0.02; these color ratios are similar to those obtained on UV excited nebulae, despite very different radiation field intensities. This supports the idea of a common origin for the near infrared radiation from excited nebulae and the diffuse interstellar medium:...