Context. Hatchell et al. (2005, A&A, 440, 151) (Paper I) published a submillimetre continuum map of the Perseus molecular cloud, detecting the starless and protostellar cores within it. Aims. To determine the evolutionary stage of each submm core in Perseus, and investigate the lifetimes of these phases. Methods. We compile spectral energy distributions (SEDs) from 2MASS (1-2 µm), Spitzer IRAC (3.6, 4.5, 5.8, 8.0 µm), Michelle (11 and 18 µm), IRAS (12, 25, 60, 100 µm), SCUBA (450 and 850 µm) and Bolocam (1100 µm) data. Sources are classified starless/protostellar on the basis of infrared and/or outflow detections and Class I/Class 0 on the basis of T bol , L bol /L smm and F 3.6 /F 850 . In order to investigate the dependence of these evolutionary indicators on mass, we construct radiative transfer models of Class 0 sources. Results. Of the submm cores, 56/103 (54%) are confirmed protostars on the basis of infrared emission or molecular outflows. Of these, 22 are classified Class 1 on the basis of three evolutionary indicators, 34 are Class 0, and the remaining 47 are assumed starless. Perseus contains a much greater fraction of Class 0 sources than either Taurus or Rho Oph. We derive estimates for the correlation between bolometric luminosity and envelope mass for Class I and Class 0 sources. Conclusions. Comparing the protostellar with the T Tauri population, the lifetime of the protostellar phase in Perseus is 0.25−0.67 Myr (95% confidence limits). The relative lifetime of the Class 0 and Class 1 phases are similar, confirming the results of Visser et al. (2002, AJ, 124, 2756 in isolated cores. We find that for the same source geometry but different masses, evolutionary indicators such as T bol vary their value. It is therefore not always appropriate to use a fixed threshold to separate Class 0 and Class I sources. More modelling is required to determine the observational characteristics of the Class 0/Class I boundary over a range of masses.

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Abstract. We present a complete survey of current star formation in the Perseus molecular cloud, made at 850 and 450 µm with SCUBA at the JCMT. Covering 3 deg 2 , this submillimetre continuum survey for protostellar activity is second in size only to that of ρ Ophiuchus (Johnstone et al. 2004, ApJ, 611, L45). Complete above 0.4 M (5σ detection in a 14 beam), we detect a total of 91 protostars and prestellar cores. Of these, 80% lie in clusters, representative of star formation across the Galaxy. Two of the groups of cores are associated with the young stellar clusters IC 348 and NGC 1333, and are consistent with a steady or reduced star formation rate in the last 0.5 Myr, but not an increasing one. In Perseus, 40-60% of cores are in small clusters (<50 M ) and isolated objects, much more than the 10% suggested from infrared studies. Complementing the dust continuum, we present a C 18 O map of the whole cloud at 1 resolution. The gas and dust show filamentary structure of the dense gas on large and small scales, with the high column density filaments breaking up into clusters of cores. The filament mass per unit length is 5-11 M per 0.1 pc. Given these filament masses, there is no requirement for substantial large scale flows along or onto the filaments in order to gather sufficient material for star formation. We find that the probability of finding a submillimetre core is a strongly increasing function of column density, as measured by C 18 O integrated intensity, P(core) ∝ I 3.0 . This power law relation holds down to low column density, suggesting that there is no A v threshold for star formation in Perseus, unless all the low-A v submm cores can be demonstrated to be older protostars which have begun to lose their natal molecular cloud.

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We present the first paper in a series detailing the results of 13CO observations of a ∼1 deg2 region of the giant molecular cloud (GMC) complex associated with the H ii region RCW 106. The 13CO observations are also the first stage of a multimolecular line study of the same region. These observations were amongst the first made using the new on‐the‐fly mapping capability of the Australia Telescope National Facility Mopra Telescope. In the configuration used, the instrument provided a full width at half‐maximum (FWHM) beam size of 33 arcsec and a velocity resolution of 0.17 km s−1. The gas emission takes the form of a string of knots, oriented along an axis that extends from the north‐west (NW) to the south‐east (SE) of the field of the observations, and which is surrounded by a more extended, diffuse emission. We analyse the 2D integrated 13CO emission using the clumpfind algorithm and identify 61 clumps. We compare the gas data in the GMC with the dust data provided by 21‐μm Midcourse Space Experiment (MSX) and 1.2‐mm Swedish European Southern Observatory Submillimetre Telescope (SEST) images that we both regridded to the cell spacing of the Mopra data and smoothed to the same resolution. The 13CO emission is more diffuse and extended than the dust emission revealed at the latter two wavebands, which both have a much higher contrast between the peaks and the extended emission. From comparison of their centre positions, we find that only ∼50 per cent of the 13CO clump fits to the data are associated with any dust clumps. Using the clump fits, the total local thermodynamic equilibrium gas mass above the 3σ level measured from the molecular data is 2.7 × 105 M⊙, whereas that measured from the smoothed 1.2‐mm SEST dust data is 2.2 × 105 M⊙.