Sensitive high frequency observations of the compact sources in Arp 220


In the last few months using snapshot EVN and VLBA observations we have detected long saught after high frequency counterparts of the 18 cm compact sources in Arp 220. The brightest sources at 6 and 3.6 cm are ¬ 1 mJy, - previous failures to detect them are apparently due to the lack, until recently, of any nearby phase-reference calbrator combined with past observations being made near sunspot maximum. Initial analysis shows a variety of source spectra. Three sources that have been detected as new sources in 18 cm monitoring show rising spectra and multifrequency light curves consistent with standard SNe models. Suprisingly most of the older sources show fairly řat high frequency spectra - the most likely reason being that these sources are interacting with the dense ULIRG ISM. One source (W42) shows good evidence for being resolved with the VLBA at 3.6 cm while others are possibly resolved. We request high freqency observations to complete an intial census of the spectra of the sources, using the highest senisitivity observations possible. We also seek to con_rm the resolution of W42 and resolve or set limits on sizes (and hence ages) of the other sources.

Name Other * Institution Email Phone
John Conway PI Onsala Space Observatory jconway@oso.chalmers.se +46-31-772-5503
Rodrigo Parra T S OSO rodrigo@oso.chalmers.se
Phil Diamond MERLIN/VLBI National Facility pdiamond@jb.man.ac.uk +44 1477 572625
Colin Lonsdale Haystack Observatory cjl@haystack.mit.edu (978) 692-4765
R. Hurley T S rosa-hurley@yahoo.co.uk
H. Thrall T S Manchester hthrall@jb.man.ac.uk
Carol Lonsdale Caltech IPAC cjl@ipac.caltech.edu (626) 397-9529
Harding Smith University of Calif - San Diego hsmith@cfa.harvard.edu
* PI = Principal Investigator; CO = Contact author; T = Thesis observations; S = Student

Front Ends
Gregorian X(8.2 to 10.0 GHz) Gregorian Ku U(12.4 to 15.4 GHz)

Back Ends
Mark 5 recorder (disks)

Type of Observing
Very Long Baseline Interferometry

Switching Type

Processor (correlator)

Allotted time 28.00 hours

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Updated 09/19/2007