Accounting for the foreground contribution to the dust emission towards Kepler's supernova remnant

Whether or not supernovae contribute significantly to the overall dust budget is a controversial subject. Submillimetre (sub-mm) observations, sensitive to cold dust, have shown an excess at 450 and 850 mu m in young remnants Cassiopeia A (Cas A) and Kepler. Some of the sub-mm emission from Cas A has been shown to be contaminated by unrelated material along the line of sight. In this paper, we explore the emission from material towards Kepler using sub-mm continuum imaging and spectroscopic observations of atomic and molecular gas, via H i, (12)CO(J = 2-1) and (13)CO(J = 2-1). We detect weak CO emission (peak T*(A) = 0.2-1 K, 1-2 km s(-1) full width at half-maximum) from diffuse, optically thin gas at the locations of some of the sub-mm clumps. The contribution to the sub-mm emission from foreground molecular and atomic clouds is negligible. The revised dust mass for Kepler's remnant is 0.1-1.2 M(circle dot), about half of the quoted values in the original study by Morgan et al., but still sufficient to explain the origin of dust at high redshifts.