Analysis of the thin layer of Galactic warm ionized gas in the range
Résumé
We present an analysis of the thin layer of Galactic warm ionized gas at an angular resolution ∼10 arcmin. This is carried out using radio continuum data at 1.4, 2.7 and 5 GHz in the coordinate region 20 • < l < 30 • , −1. • 5 < b < +1. • 5. For this purpose, we evaluate the zero level of the 2.7-and 5-GHz surveys using auxiliary data at 2.3 GHz and 408 MHz. The derived zero-level corrections are T zero (2.7 GHz) = 0.15 ± 0.06 K and T zero (5 GHz) = 0.1 ± 0.05 K. We separate the thermal (free-free) and non-thermal (synchrotron) component by means of a spectral analysis performed adopting an antenna temperature spectral index −2.1 for the free-free emission, a realistic spatial distribution of indices for the synchrotron radiation and by fitting, pixel-by-pixel, the Galactic spectral index. We find that at 5 GHz, for |b| = 0 • , the fraction of thermal emission reaches a maximum value of 82 per cent, while at 1.4 GHz, the corresponding value is 68 per cent. In addition, for the thermal emission, the analysis indicates a dominant contribution of the diffuse component relative to the source component associated with discrete H II regions.
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