AN UPPER LIMIT ON ANOMALOUS DUST EMISSION AT 31 GHz IN THE DIFFUSE CLOUD [LPH96] 201.663 1.643
نویسندگان
چکیده
[LPH96] 201.663 1.643, a diffuse H ii region, has been reported to be a candidate for emission from rapidly spinning dust grains. We present Cosmic Background Imager (CBI) observations at 26–36 GHz that show no evidence for significant anomalous emission. The spectral index within the CBI band, and between CBI and Effelsberg data at 1.4 and 2.7 GHz, is consistent with optically thin free-free emission. The best-fitting temperature spectral index from 2.7 to 31 GHz, bp 2.06 0.03, is close to the theoretical value, bp 2.12 for Te p 9100 K. We place an upper limit of 24% (2 j) for excess emission at 31 GHz as seen in a 6 FWHM beam. Draine & Lazarian spinning-dust models, with typical grain properties, are not a good fit to the spectrum of LPH96 when both Green Bank and CBI data are included. No polarized emission is detected in the CBI data, with an upper limit of 2% on the polarization fraction. Subject headings: dust, extinction — ISM: individual ([LPH96] 201.663 1.643) — polarization — radiation mechanisms: general — radio continuum: ISM
منابع مشابه
Tentative Detection of Electric Dipole Emission from Rapidly Rotating Dust Grains
We present the first tentative detection of spinning dust emission from specific astronomical sources. All other detections in the current literature are statistical. The Green Bank 140 foot telescope was used to observe 10 dust clouds at 5, 8, and 10 GHz. In some cases, the observed emission was consistent with the negative spectral slope expected for free-free emission (thermal bremsstrahlung...
متن کاملInfrared-correlated 31-GHz radio emission from Orion East
Lynds dark cloud LDN1622 represents one of the best examples of anomalous dust emission, possibly originating from small spinning dust grains. We present Cosmic Background Imager (CBI) 31-GHz data of LDN1621, a diffuse dark cloud to the north of LDN1622 in a region known as Orion East. A broken ring-like structure with diameter ≈20 arcmin of diffuse emission is detected at 31 GHz, at ≈20–30 mJy...
متن کاملCBI limits on 31 GHz excess emission in southern H ii regions
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 Hii 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 fre...
متن کاملAnomalous Radio Emission from Dust in the Helix
A by-product of experiments designed to map the cosmic microwave background is the recent detection of a new component of foreground Galactic emission. The anomalous foreground at 10–30 GHz, unexplained by traditional emission mechanisms, correlates with 100 m dust emission. We use planetary nebulae (PNs) as astrophysical laboratories to test known radio emission processes and report that in th...
متن کاملAnomalous emission from HII regions
Spinning dust appears to be the best explanation for the anomalous emission that has been observed at ∼ 10 − 60 GHz. One of the best examples of spinning dust comes from a HII region in the Perseus molecular cloud. Observations of other HII regions also show tentative evidence for excess emission at frequencies ∼ 30 GHz, although at lower emissivity levels. A new detection of excess emission at...
متن کامل