Star formation in Sandqvist 187 and 188

Abstract

We present 1.2 mm continuum data of the filamentary dark cloud Sandqvist 187/188 - also known as the Norma cloud - taken with SIMBA (SEST Imaging Bolometer Array). The data are complemented by measurements from the 2MASS, MSX and IRAS surveys. The extended 1.2 mm emission traces the optical dark cloud down to a visual extinction of AV = 3.7 mag. We derive a mean column density of N(H2) = 1.4 × 1022 cm-2, equivalent to a visual extinction of AV = 7.6 mag and a total mass of the cloud of 340 M⊙. We also find six compact millimetre sources, labelled MMS 1 to 6, five of which coincide with known stellar objects. MMS 6, however, only has a very weak MSX counterpart at 14.56 μm and an absorption feature at 8.28 μm consistent with a visual extinction of A V > 145 mag. Dust temperatures, luminosities and gas masses for all compact millimetre sources are given. In an effort to further constrain the uncertain distance to Sandqvist 187/188, we analyse its stellar content based on 2MASS colours and find an improved lower limit of 440 ± 50 pc. © ESO 2005.