Tracing the mass during low-mass star formation. I. Submillimeter continuum observations

We have obtained 850 and 450 mum continuum maps of 21 low-mass cores with SEDs ranging from pre-protostellar to Class I (18 K < T-bol < 370 K), using SCUBA at the JCMT. In this paper we present the maps, radial intensity profiles, and photometry. Pre-protostellar cores do not have power-law intensity profiles, whereas the intensity profiles of Class 0 and Class I sources can be fitted with power laws over a large range of radii. A substantial number of sources have companion sources within a few arcminutes (two out of five pre-protostellar cores, nine out of 16 Class 0/1 sources). The mean separation between sources is 10,800 AU. The median separation is 18,000 AU including sources without companions as a lower limit. The mean value of the spectral index between 450 and 850 mum is 2.8 +/- 0.4, with pre-protostellar cores having slightly lower spectral indices (2.5 +/- 0.4). The mean mass of the sample, based on the dust emission in a 120 aperture, is 1.1 +/- 0.9 M.. For the sources fitted by power-law intensity distributions (I-v(b)/I-v(0) = (b/b(0))(m)), the mean value of m is 1.52 +/- 0.45 for Class 0 and I sources at 850 mum and 1.44 +/- 0.25 at 450 mum Based on a simple analysis, assuming the emission is in the Rayleigh-Jeans limit and that T-d(r) proportional to r(-0.4), these values of m translate into power-law density distributions (n proportional to r(-p)) with p similar to 2.1 However, we show that this result may be changed by more careful consideration of effects such as beam size and shape, finite outer radii, more realistic T-d(r), and failure of the Rayleigh-Jeans approximation.