| 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. |
