The Characteristics Of Filamentary Structures In The Orion A Giant Molecular Cloud

This study is focused on the properties of the molecular filaments in the Orion A giant molecular cloud(GMC).We have made a simultaneous survey of 12CO,13CO and 19CO(J=1-0)emission toward the Orion A GMC with a sky coverage of?4.4 deg2 using the PMO-13.7 m millimeter-wavelength telescope.We calculate H2 column densities of Orion A GMC using 12CO and 13CO emission under the local thermal equi-librium assumption.225 filaments are identified in the H2 column density map,using the DisPerSE algorithm.We selected 46 prominent filaments with lengths above 1.2 pc to analyze the corresponding column density profiles in detail.We divided the selected filaments into 397 molecular segments with similar lengths and calculated the column density profiles for each segment.The symmetries of the profiles are manually investi-gated.About 60.4%of the column density profiles are intrinsically asymmetrical,and 15.4%of the column density profiles are intrinsically symmetrical,while the intrinsic symmetries of 24.2%of the segments are unknown.Based on the intrinsic and observed symmetries,we divided these segments into eight categories.The selected symmetrical profiles are fitted with both Gaussian functions and Plummer-like functions.The typical widths of the filaments are obtained through the statistics of the fitted full width at half maximum(FWHM)parameters of the two fitting methods,?0.36 pc from Gaussian fitting and?0.39 pc from the Plummer-like function fitting,respectively.The median value of FWHM widths derived from the second moment method is?0.53 pc.The seg-ment widths increase systematically from north to south.There is a close association between the filamentary structures and the young stellar objects in the Orion A GMC.