NAM logo, by David Le Conte

Global VLBI observations of M82

T.W.B.Muxlow, A.Pedlar, P.J.Diamond, S.T.Garrington K.A.Wills, A.McDonald, P.N.Wilkinson, M.A.Garrett (Jodrell)

We present preliminary results from the analysis of a Global VLBI observation in November 1998. This was the first 20-station simultaneous correlation performed at the VLBA correlator. Data were taken in wide-field mode with 3 fringe rotation centres across the central 1 kpc (1 arcminute) of M82. These results are from data centred on the most compact radio source in M82 (41.95+575). Visible are both 41.95+575 and the next most compact SNR, 43.31+592, which lies around 7 arcseconds to the North-East of 41.95+575.

41.95+575 shows a very unusual radio structure. It has been monitored with VLBI for more than 10 years and has been found to be decreasing in flux density at about 8% per year, but has a low expansion velocity of <2500 km/s. It is unclear if this is an SNR or some sort of collimated outflow. Its projected zero age is in the mid 1950s.

43.31+592 is a more conventional SNR with a beautiful shell structure. At the high angular resolution of the latest Global VLBI images its detailed structure is revealed for the first time. It resembles Cassiopeia A, but is a lot smaller with a diameter of 2.1 light years. EVN images from 1986 and 1997 show this shell to be expanding with a measured velocity of 9500 km./s. Projecting the diameter back to zero size gives a birth date in the mid 1960s implying that this is the youngest SNR in M82.

Maintained by Ian Howarth