The JCMT Gould Belt Survey Complete Core Catalogue: Core mass function variations between nearby molecular clouds

TL;DR

The paper delivers a large, self-consistent catalogue of dense cores in 12 nearby molecular clouds from JCMT GBS SCUBA-2 data, identifying 2257 cores with 59% starless and 41% protostellar populations. Using Bonnor–Ebert stability analyses and distance-aware completeness simulations, it shows CMFs are well described by log-normal forms but are not drawn from a single underlying CMF; the peak core mass increases with cloud mass and the maximum starless core mass follows $M_{ ext{max}} \\propto M_{ ext{cloud}}^{0.58 \\pm \\ 0.13}$, consistent with cluster-scale star formation trends. The prestellar CMF peak is about 3 times the Chabrier IMF peak, implying a ~33% core-to-star efficiency, while nearby clouds exhibit notable CMF variations likely tied to environmental factors. Overall, the findings suggest CMFs are environment-dependent and that larger, more distant clouds are needed to fully sample the high-mass end of the CMF and better connect CMFs to the stellar IMF.

Abstract

We present a catalogue of dense cores identified in James Clerk Maxwell Telescope (JCMT) Gould Belt Survey SCUBA-2 observations of nearby star-forming clouds. We identified 2257 dense cores using the getsources algorithm, of which 59% are starless, and 41% are potentially protostellar. 71% of the starless cores are prestellar core candidates, suggesting a prestellar core lifetime similar to that of Class 0/I YSOs. Higher-mass clouds have a higher fraction of prestellar cores compared to protostars, suggesting a longer average prestellar core lifetime. We assessed completeness by inserting critically-stable Bonnor--Ebert spheres into a blank SCUBA-2 field: completeness scales as distance squared, with an average mass recovery fraction of $73\pm6$% for recovered sources. We calculated core masses and radii, and assessed their gravitational stability using the Bonnor-Ebert criterion. Maximum starless core mass scales with cloud complex mass with an index $0.58\pm 0.13$, consistent with the behaviour of maximum stellar masses in embedded clusters. We performed least-squares and Monte Carlo modelling of the core mass functions (CMFs) of our starless and prestellar core samples. The CMFs can be characterised using log-normal distributions: we do not sample the full range of core masses needed to create the stellar Initial Mass Function (IMF). The CMFs of the clouds are not consistent with being drawn from a single underlying distribution. The peak mass of the starless core CMF increases with cloud mass; the prestellar CMF of the more distant clouds has a peak mass $\sim 3\times$ the log-normal peak for the system IMF, implying a $\sim 33$% prestellar core-to-star efficiency.

Figures (76)

• Figure 1: Extracts from three of the regions which we observed with SCUBA-2 as part of the JCMT Gould Belt Survey: the Integral Filament in Orion A (left), the L1688 region of the Ophiuchus Molecular Cloud (top right), and the Serpens North region (bottom right). Each panel shows SCUBA-2 850 $\upmu$m emission, fourth-root scaled in the case of Orion A, and cube-root scaled for the other regions. Cores identified in our catalogue are marked with black ellipses, with ellipse diameter marking the FWHM size of the core. A 0.5 pc scale bar is shown in the lower left-hand corner of each panel; the JCMT 850 $\upmu$m beam size is shown as a filled black circle in the lower right-hand corner. The full set of regions observed are shown in Appendix \ref{['sec:appendix_images']}.
• Figure 2: Representative rms values per mosaic at 850 $\upmu$m and 450 $\upmu$m. The dashed lines show the median rms per observing field (see text for more details). The points are colour-coded to the approximate distance to each cloud, as used in later analysis.
• Figure 3: The fraction of material at a given Herschel Gould Belt Survey column density or higher mapped by the JCMT GBS. The vertical dashed line shows a column density of $N({\rm H}_{2}) = 1.4\times10^{22}$ cm$^{-2}$, which corresponds approximately to the JCMT GBS mapping goal of $A_{V} \gtrsim 7$ mag. Each line represents a different cloud complex that we consider.
• Figure 4: Fraction of input BEC spheres returned by getsources as a function of input source mass, for sources at distances of 150 pc (red circles), 300 pc (green squares) and 450 pc (blue triangles). Solid black line marks 100% completeness; dashed line marks 95% completeness; dotted line marks 90% completeness.
• Figure 5: Our estimated 90% mass completenesses as a function of distance. A quadratic fit to the data is shown. The lowest-mass source detected in IC 5146 is shown as a lower limit for mass completeness at this distance.