Photographic imaging of light echoes from SN 1987A

The light echoes from SN 1987 A have been photographed at the prime focus of the 3.9-m Anglo-Australian Telescope. The bright emission nebulosity and large number of faint stars in the field have been cancelled from the images by photographic subtraction. A more comprehensive view of the echoes results, revealing that the two previously known arcs are complete circles. Two new echo features are also revealed: an arc just interior to the inner ring over a small range of position angle, and a compact spot which appears to be part of a linear dust feature. The geometry of the echo rings has been deduced from measuring-machine scans of the subtracted image. The inner ring is found to be concentric about the supernova, indicating that the illuminated cloud of dust, which lies ~ 130 pc in front of the supernova, is roughly normal to the line-of-sight. The outer ring is significantly eccentric about the supernova with its maximum displacement at PA = 29°, in the direction of the nearby OB association NGC 2044. This cloud is therefore inclined to the line-of-sight to the supernova. The possibility is discussed that both clouds are part of the N 157C supershell centred on NGC 2044.