CO J=2-1 LINE OBSERVATIONS TOWARD THE SUPERNOVA REMNANT G54.1+0.3

We present (CO)-C-12 J = 2-1 line observations of G54.1+0.3, a composite supernova remnant with a mid-infrared (MIR) loop surrounding the central pulsar wind nebula (PWN). We map an area of 12' x 9' around the PWN and its associated MIR loop. We confirm two velocity components that have been proposed to be possibly interacting with the PWN/MIR-loop; the +53 km s(-1) cloud, which appears in contact with the eastern boundary of the PWN and the +23 km s(-1) cloud, which has CO emission coincident with the MIR loop. However, we have not found a direct evidence for the interaction in either of these clouds. Instead, we detected an 5'-long arc-like cloud at +15-+23 km s(-1) with a systematic velocity gradient of similar to 3 km s(-1) arcmin(-1) and broad-line emitting CO gas with widths (FWHM) of less than or similar to 7 km s(-1) in the western interior of the supernova remnant. We discuss their association with the supernova remnant.