Recombination Lines near 8·9 GHz of Strong Sources in the Southern Milky Way

McGee, R. X.; Newton, Lynette M.; Batchelor, R.

doi:10.1071/ph750185

Cited by 8 publications

(17 citation statements)

References 9 publications

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“…Above 5 GHz, the emission appears to be optically thin and is best fitted by a power law over the range 5-150 GHz (omitting the CBI data point) with flux density spectral index, α = −0.115 ± 0.023. This agrees well with the theoretical value of α ≈ −0.12 for ν ∼ 30 GHz and T e ≈ 7500 K (McGee et al 1975;Caswell & Haynes 1987). From visibility-visibility correlations with the Parkes 6-cm map (Haynes, Caswell & Simons 1978), we found a consistent value of α = −0.06 ± 0.10.…”

Section: R E S U Lt Ssupporting

confidence: 91%

“…Similarly, the lower resolution Wilkinson Microwave Anisotropy Probe ( WMAP ) data (Bennett et al 2003a) are sensitive to local extended emissions. The data points are at 0.4 and 5 GHz (Shaver & Goss 1970b), 2.7 GHz (Day, Caswell & Cooke 1972), 8.9 GHz (McGee, Newton & Batchelor 1975), 14.7 GHz (McGee & Newton 1981), 90 and 150 GHz 5 (Coble et al 2003) and 300 GHz (Cheung et al 1980). The free–free emission is clearly optically thick at 408 MHz and turnover at ∼1 GHz.…”

Section: Resultsmentioning

confidence: 99%

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CBI limits on 31 GHz excess emission in southern H II regions

Dickinson

Davies

Bronfman

et al. 2007

Monthly Notices of the Royal Astronomical Society

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We have mapped four regions of the southern Galactic plane at 31 GHz with the Cosmic Background Imager. From the maps, we have extracted the flux densities for six of the brightest H ii regions in the southern sky and compared them with multifrequency data from the literature. The fitted spectral index for each source was found to be close to the theoretical value expected for optically thin free–free emission, thus confirming that the majority of flux at 31 GHz is due to free–free emission from ionized gas with an electron temperature of ≈7000–8000 K. We also found that, for all six sources, the 31‐GHz flux density was slightly higher than the predicted value from data in the literature. This excess emission could be due to spinning dust or another emission mechanism. Comparisons with 100‐μm data indicate an average dust emissivity of 3.3 ± 1.7 μK (MJy sr−1)−1, or a 95 per cent confidence limit of <6.1 μK (MJy sr−1)−1. This is lower than that found in diffuse clouds at high Galactic latitudes by a factor of ∼3–4. The most significant detection (3.3σ) was found in G284.3−0.3 (RCW 49) and may account for up to ≈30 per cent of the total flux density observed at 31 GHz. Here, the dust emissivity of the excess emission is 13.6 ± 4.2 μK (MJy sr−1)−1 and is within the range observed at high Galactic latitudes. Low‐level polarized emission was observed in all six sources with polarization fractions in the range 0.3–0.6 per cent. This is likely to be mainly due to instrumental leakage and is therefore an upper limit to the free–free polarization. It corresponds to an upper limit of ∼1 per cent for the polarization of anomalous emission.

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Section: R E S U Lt Ssupporting

confidence: 91%

Section: Resultsmentioning

confidence: 99%

CBI limits on 31 GHz excess emission in southern H II regions

Dickinson

Davies

Bronfman

et al. 2007

Monthly Notices of the Royal Astronomical Society

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“…However, for the H 901X line, where the telescope beam is 2' ·6 arc at half-power points, TdTc is 4· 4 %, i.e. 48 % of the galactic expectation of 9·1 % (McGee et al 1974). The spectral index, a: = -0·2, for 30 Doradus also points to the presence of non thermal components in the central core source of this complex.…”

Section: Ratio Of Line-to-continuum Temperaturementioning

confidence: 99%

“…The ratio by number N(He+)/N(H+) = 0 ·08 (less than half the value reported by Mezger et al 1970). It is equal to the average ratio obtained from 17 southern Milky Way objects observed in H, He 90ot: lines (McGee et al 1974). The intensity of the H 137/3 line is such that the temperature ratio TH137P/THI09a is 0·25.…”

Section: Other Recombination Lines In 30 Doradus and Me 77mentioning

confidence: 99%

Recombination Lines near 6 cm Wavelength in the Large Magellanic Cloud

McGee¹,

Newton²,

Brooks³

1974

Aust. J. Phys.

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Recombination lines H 10901: have been detected in eight sources in the Large Cloud of Magellan. Low ratios of line temperature to continuum temperature, TdTc, were found in most of the sources and are attributed to the difficulty of obtaining a true continuum value when such a large area is encompassed by the telescope beam. In the 30Doradus nebula the ratio N(He+)jN(H+) was found to be no greater than O' 08, or less than half that previously recorded by radio observations.

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“…The northernmost nebula, M17, has been studied most intensely, whilst observations of the other four sources, all made with the Parkes radiotelescope, have produced far less data. Used in the analysis were the line data summarized by Hjellming and Gordon (1971), together with measurements by McGee and Gardner (1968), McGee et al (1969), Gardner et al (1970aGardner et al ( , 1970b, Simpson (1970), Wilson et al (1970), Pedlar and Davies (1972), Waltman and Johnston (1973), Batty (1974), , Huchtmeier (1974) and McGee et al (1975).…”

Section: Recombination Line Datamentioning

confidence: 99%

Models of Radio Recombination Line Sources

Batty¹

1979

Aust. J. Phys.

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Models for the southern HII regions RCW38, RCW49, the Carina Nebula, G305+0 and M17 are constructed using a range of line and continuum data. Electron temperatures in the range 5000-7300 K are derived from the analysis, and in most cases these are consistent with estimates obtained from radio continuum measurements. The presence of a low temperature (.;; 4000 K) outer region in RCW 38 is suggested by the low frequency line data. Density inhomogeneities are found to be significant in all sources, while the predicted line widths are consistent with an observed lack of collisional broadening at low frequencies.

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Recombination Lines near 8·9 GHz of Strong Sources in the Southern Milky Way

Cited by 8 publications

References 9 publications

CBI limits on 31 GHz excess emission in southern H II regions

CBI limits on 31 GHz excess emission in southern H II regions

Recombination Lines near 6 cm Wavelength in the Large Magellanic Cloud

Models of Radio Recombination Line Sources

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