Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
Abstract: We have obtained column density maps for an unbiased sample of 120 molecular
clouds in the third quadrant of the Milky Way mid-plane (b$\le |5|^{\circ}$)
within the galactic longitude range from 195$^{\circ}$ to 225$^{\circ}$, using
the high sensitivity $^{12}$CO and $^{13}$CO ($J=1-0$) data from the Milky Way
Imaging Scroll Painting (MWISP) project. The probability density functions of
the molecular hydrogen column density of the clouds, N-PDFs, are fitted with
both log-normal (LN) function and log-normal plus power-law (LN+PL) function.
The molecular clouds are classified into three categories according to their
shapes of N-PDFs, i.e., LN, LN+PL, and UN (unclear), respectively. About 72\%
of the molecular clouds fall into the LN category, while 18\% and 10\% into the
LN+PL and UN categories, respectively. A power-law scaling relation,
$\sigma_s\propto N_{H_2}^{0.44}$, exists between the width of the N-PDF,
$\sigma_s$, and the average column density, $N_{H_2}$, of the molecular clouds.
However, $\sigma_s$ shows no correlation with the mass of the clouds. A
correlation is found between the dispersion of normalized column density,
$\sigma_{N/\rm
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
Abstract: We identify 225 filaments from an H$_2$ column density map constructed using simultaneous $^{12}$CO, $^{13}$CO, and C$^{18}$O (J=1-0) observations carried out as a part of the MWISP project. We select 46 long filaments with lengths above 1.2 pc to analyze the filament column density profiles. We divide the selected filaments into 397 segments and calculate the column density profiles for each segment. The symmetries of the profiles are investigated. The proportion of intrinsically asymmetrical segments is 65.3$\%$, and that of intrinsically symmetrical ones is 21.4$\%$. The typical full width at half maximum (FWHM) of the intrinsically symmetrical filament segments is $\sim$ 0.67 pc with the Plummer-like fitting, and $\sim$ 0.50 pc with the Gaussian fitting, respectively. The median FWHM widths derived from the second-moment method for intrinsically symmetrical and asymmetrical profiles are $\sim$ 0.44 and 0.46 pc, respectively. Close association exists between the filamentary structures and the YSOs in the region.
Peer Review Status:Awaiting Review