Tracing the Mass during Low-Mass Star Formation. I. Submillimeter Continuum Observations

Abstract

We have obtained 850 and 450 micron continuum maps of 21 low mass cores with SED's ranging from pre-protostellar to Class I (18K < Tbol < 370K), 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 (2 out of 5 pre-protostellar cores, 9 out of 16 Class 0/I sources). The mean separation between sources is 10800 AU. The median separation is 18000 AU including sources without companions as a lower limit. The mean value of the spectral index between 450 and 850 microns is 2.8 +- 0.4, with PPCs having slightly lower spectral indices (2.5 +- 0.4). The mean mass of the sample, based on the dust emission in a 120 arcsecond aperture, is 1.1 +- 0.9 solar masses. For the sources fitted by power-law intensity distributions (I_nu(b)/I_nu(0) = (b/b_0) ^ m), the mean value of m is 1.52 +- 0.45 for Class 0 and I sources at 850 microns and 1.44 +- 0.25 at 450 microns. Based on a simple analysis, assuming the emission is in the Rayleigh-Jeans limit and that T_d(r) ~ r ^ {-0.4}, these values of m translate into power-law density distributions (n ~ r ^ {-p}) with p ~ 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.