The initial conditions of isolated star formation -- IX. Akari mapping of an externally heated pre-stellar core

Abstract

We present observations of L1155 and L1148 in the Cepheus molecular cloud, taken using the FIS instrument on the Akari satellite. We compare these data to submillimetre data taken using the SCUBA camera on the JCMT, and far-infrared data taken with the ISOPHOT camera on board the ISO satellite. All of the data show a relation between the position of the peak of emission and the wavelength for the core of L1155. We interpret this as a temperature gradient. We fit modified blackbody curves to the spectral energy distributions at two positions in the core and see that the central core in L1155 (L1155C) is approximately 2 degrees warmer at one edge than it is in the centre. We consider a number of possible heating sources and conclude that the A6V star BD+67 1263 is the most likely candidate. This star is at a distance of 0.7 pc from the front of L1155C in the plane of the sky. We carry out radiative transfer modelling of the L1155C core including the effects from the nearby star. We find that we can generate a good fit to the observed data at all wavelengths, and demonstrate that the different morphologies of the core at different wavelengths can be explained by the observed 2 degree temperature gradient. The L1148 core exhibits a similar morphology to that of L1155C, and the data are also consistent with a temperature gradient across the core. In this case, the most likely heating source is the star BD197053. Our findings illustrate very clearly that the apparent observed morphology of a pre-stellar core can be highly dependent on the wavelength of the observation, and that temperature gradients must be taken into account before converting images into column density distributions. This is important to note when interpreting Akari and Spitzer data and will also be significant for Herschel data.

15 pages, 15 figures, accepted by MNRAS

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Cited by in corpus (11)

• The earliest phases of star formation - A Herschel key project. The thermal structure of low-mass molecular cloud cores
• The Earliest Phases of Star formation observed with Herschel (EPoS): The dust temperature and density distributions of B68
• The Spitzer survey of interstellar clouds in the Gould Belt. II. The Cepheus Flare observed with IRAC and MIPS
• The dense cores and filamentary structure of the molecular cloud in Corona Australis. Herschel SPIRE and PACS observations from the Herschel Gould Belt Survey
• The JCMT and Herschel Gould Belt Surveys: A comparison of SCUBA-2 and Herschel data of dense cores in the Taurus dark cloud L1495
• The JCMT Gould Belt Survey: First results from SCUBA-2 observations of the Cepheus Flare Region
• Confirmation of the VeLLO L1148-IRS: Star Formation at very low (Column) Density
• The initial conditions of isolated star formation - X. A suggested evolutionary diagram for prestellar cores
• Modelling Herschel observations of infrared-dark clouds in the Hi-GAL survey
• Core orientations and magnetic fields in isolated molecular clouds
• Dense Molecular Cores Being Externally Heated