GALACTIC PLANE OBSERVATIONS AT 31 GHZ WITH THE COSMIC BACKGROUND IMAGER

Abstract

Anomalous Microwave Emission (AME) is a dust-correlated diffuse foreground discoveredin the late 1990's. It is believed to emit in the frequency range of 10-60 GHzpeaking at ~30 GHz, while its spectral index depends strongly on frequency. Itsorigins and attributes are yet to be fully understood. This has motivated this study,which searched for AME sources at 31 GHz and ~4.5 arcmin resolution, in regionsclose to the Galactic plane using the Cosmic Background Imager. The survey consistsof 110 individual pointings of two areas, covering ~30 square degrees in total.The data were obtained in differenced mode i.e a number of fields were observedat the same declination and separated by a few minutes in Right Ascension. Thenthe fields being further away from the Galactic plane were used to subtract theground pickup from the rest. The data were edited and calibrated using the CBIdata reduction pipeline. The reduced data were imaged and CLEANed using thesoftware DIFMAP. The CBI maps were found to be limited by true dynamic rangeat a level of ~100:1.Three bright sources of emission stand out in both maps, the NGC 6334, NGC 6357and W51 complexes. An analysis of the bright sources was performed using aperturephotometry. The CBI data were compared with archival radio data at 2.7 and 5GHz. Most sources were found to be consistent with optically thin free-free emission.A comparison of the limits on excess emission with 100 micro metre data indicate anaverage dust emissivity of 0.3 ± 1.0 μK(MJy sr-1)-1, or a 95% upper limit of

Date of Award	3 Jan 2013
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Clive Dickinson (Supervisor) & Scott Kay (Supervisor)