ASTRONOMY AND ASTROPHYSICS Galactic Hα emission and the cosmic microwave background
Abstract. We present observations of Galactic Hα emission along two declination bands where the South Pole cosmic microwave background experiment reports temperature fluctuations. The high spectral resolution of our Fabry–Perot system allows us to separate the Galactic signal from the much larger lo...
| Main Authors: | , , , , |
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.388.8422 http://aa.springer.de/papers/8338001/2300001.pdf |
| Summary: | Abstract. We present observations of Galactic Hα emission along two declination bands where the South Pole cosmic microwave background experiment reports temperature fluctuations. The high spectral resolution of our Fabry–Perot system allows us to separate the Galactic signal from the much larger local sources of Hα emission, such as the Earth’s geocorona. For the two bands (at δ = −62 ◦ and −63 ◦), we find a total mean emission of ∼ 1 R with variations of ∼ 0.3 R. The variations are within the estimated uncertainty of our total intensity determinations. For an ionized gas at T ∼ 10 4 K, this corresponds to a maximum free–free brightness temperature of less than 10 µK at 30 GHz (K–band). Thus, unless there is a hot gas component with T ∼ 10 6 K, our results imply that there is essentially no free–free contamination of the SP91 (Schuster et al. 1993) and SP94 (Gunderson et al. 1995) data sets. Key words: cosmic microwave background – diffuse radiation – Galaxy: halo – ISM: general 1. |
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