The JCMT Gould Belt Survey: evidence for radiative heating and contamination in the W40 complex

Abstract

We present SCUBA-2 450 µm and 850 µm observations of the W40 complex in the Serpens-Aquila region as part of the James Clerk Maxwell Telescope (JCMT) Gould Belt Survey (GBS) of nearby star-forming regions. We investigate radiative heating by con- structing temperature maps from the ratio of SCUBA-2 fluxes using a fixed dust opacity
spectral index, β = 1.8, and a beam convolution kernel to achieve a common 14.811 res- olution. We identify 82 clumps ranging between 10 and 36 K with a mean temperature of 20±3 K. Clump temperature is strongly correlated with proximity to the external OB association and there is no evidence that the embedded protostars significantly heat the dust. We identify 31 clumps that have cores with densities greater than 105cm−3. Thir- teen of these cores contain embedded Class 0/I protostars. Many cores are associated with bright-rimmed clouds seen in Herschel 70 µm images. From JCMT HARP observations of
the 12CO 3–2 line, we find contamination of the 850 µm band of up to 20 per cent. We
investigate the free-free contribution to SCUBA-2 bands from large-scale and ultracompact H ii regions using archival VLA data and find the contribution is limited to individual stars, accounting for 9 per cent of flux per beam at 450 µm or 12 per cent at 850 µm in these cases. We conclude that radiative heating has potentially influenced the formation of stars in the Dust Arc sub-region, favouring Jeans stable clouds in the warm east and fragmentation in
the cool west.
Key words: radiative transfer, catalogues, stars: formation, ISM: H II regions, submil- limetre: general