Comparison of Herschel and ArTéMiS observations of massive filaments

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Context. Filaments are a fundamental part of the interstellar medium (ISM). Their morphology and fragmentation can offer crucial information on the nature of the ISM and star formation. OMC-3 in the Orion A Cloud is a nearby, high-mass, star-forming region, which offers an ideal opportunity to study massive filaments in detail. Aims. We analyze how the inclusion of higher resolution data affects estimates of the filament properties, including their widths and fragmentation properties. We also test the robustness of filament fitting routines. Methods. We combined the ArTéMiS and Herschel data to create high-resolution images. The column densities and temperatures were estimated via a modified blackbody fitting. We compared the nearby OMC-3 cloud (d = 400 pc) to the more distant G202 and G17 clouds (d = 760 and 1850 pc, respectively). We further compared the appearance of the OMC-3 cloud at the Herschel and ArTéMiS resolution. Results. Column densities of dense clumps in OMC-3 are higher in the combined ArTéMiS and Herschel data (FWHM ∼ 8.5′′) when compared to Herschel-only data (FWHM ∼ 20′′). The estimated filament widths are smaller in the combined maps and also show signs of further fragmentation when observed with the ArTéMiS resolution. In this analysis of Herschel data, the estimated filament widths are correlated with the distance of the field. Conclusions. The median filament full width at half maximum (FWHM) in OMC-3 at the higher resolution is 0.05 pc, whereas it is 0.1 pc with the Herschel resolution, and then 0.3 pc in G202 and 1.0 pc in G17, also at the Herschel resolution. It is unclear what causes the steep relation between the distance and filament FWHM values, however, likely reasons include the effect of the limited telescope resolution combined with existing hierarchical structure, along with the convolution of large-scale background structures within the ISM. Estimates of the asymptotic power-law index of the filament profile function, p, are high. When fit with the Plummer function, the individual parameters of the profile function are degenerate, while the FWHM is better constrained. OMC-3 displays negative kurtosis, while all structures but OMC-3 at the Herschel resolution reveal some asymmetry.

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