Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 1998
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998mnras.301..585v&link_type=abstract
Monthly Notices of the Royal Astronomical Society, Volume 301, Issue 2, pp. 585-592.
Astronomy and Astrophysics
Astronomy
44
Circumstellar Matter, Stars: Formation, Ism: Individual: Ngc 2024, Ism: Molecules
Scientific paper
We present 450- and 800-μm images, made with the James Clerk Maxwell Telescope, of the NGC 2024 molecular ridge. The seven previously known compact cores, FIR1-7, have been detected, and FIR5 has been resolved into a compact object and an associated extended source to the east. The estimated masses of the dense cores vary between 1.6 and 5.1Msolar per 14-arcsec beam, assuming a dust temperature of 30K and a dust opacity of kappa_800mum=0.002 m^2 kg^-1. A spectral index map made from the 450- and 800-μm images shows spatial variations, with the spectral index, alpha (F_nu~nu^alpha), being systematically lower towards the dense cores. We interpret this as evidence for a lower value of the frequency dependence of the dust opacity, beta, towards the denser cores relative to the surrounding molecular material. This may indicate that grain growth is occurring in the cores, prior to planetesimal formation. By comparing the high-resolution 450-μm image with interferometer maps of the integrated CS(2-1) emission, the previously reported discrepancy between dust continuum emission and molecular line emission is found to be very localized. Depletion and temperature variations are discussed as possible explanations.
Chandler Claire J.
Padman Rachael
Richer John S.
Visser Anja E.
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