Protostars and Planets VI, Heidelberg, July 15-20, 2013
PROFILING FILAMENTS: COMPARING NEAR-INFRARED EXTINCTION AND SUBMILLIMETRE DATA IN TMC-1
Malinen, Johanna (University of Helsinki)
Juvela, Mika (University of Helsinki)
Rawlings, Mark (NRAO)
Interstellar filaments are an important part of the star formation process. To understand the structure and formation of filaments, the filament cross-section profiles are often fitted with the Plummer profile function. Currently this profiling is often approached with submm studies, especially with Herschel. If these data are not available, it would be convenient if filament properties could be studied using groundbased near-infrared (NIR) observations. We compare the filament profiles obtained by NIR extinction and submm observations to find out if reliable profiles can be derived using NIR data. We use J-, H-, and K-band data of a filament north of TMC-1, which we call TMC-1N, to derive an extinction map from colour excesses of background stars. We compare the Plummer profiles obtained from these extinction maps with Herschel dust emission maps. We present two new methods to estimate profiles from NIR data: Plummer profile fits to median Av of stars within certain offset or directly to the Av of individual stars. We compare these methods by simulations. In simulations the extinction maps and the new methods give correct results to within 10-20% for modest densities. The direct fit to data on individual stars usually gives more accurate results than the extinction map, and can work in higher density. In the profile fits to real observations, the values of Plummer parameters are generally similar to within a factor of ∼2. The parameter values can vary significantly, but the estimates of filament mass usually remain accurate to within some tens of per cent. NIR extinction maps can be used as an alternative to submm data to profile filaments. However, Plummer profile parameters are not always well constrained, and caution should be taken when making the fits. In the evaluation of the Plummer parameters, one can make use of the independence of dust emission and NIR data and the difference in the shapes of the confidence regions. We also present studies of filaments using NIR scattered light and 3D MHD simulations.
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