Molecular Clouds in the Second Quadrant of the Milky Way Mid-plane from l$=$104$.\!\!^{\circ}$75 to l=119$.\!\!^{\circ}$75 and b=$-$5$.\!\!^{\circ}$25 to b=5$.\!\!^{\circ}$25

TL;DR

This study analyzes molecular cloud properties in a specific Milky Way region using CO emission data, revealing differences in cloud mass, size, and density between the Perseus and Local arms, and examining their density distribution functions.

Contribution

It provides a detailed catalog of molecular clouds in the second Galactic quadrant and analyzes their physical properties and density distributions, highlighting arm-dependent variations.

Findings

Perseus arm clouds are significantly more massive and larger than Local arm clouds.

Most clouds have log-normal density PDFs with small deviations at high densities.

A subset of clouds exhibits power-law density PDFs associated with star-forming regions.

Abstract

We have studied the properties of molecular clouds in the second quadrant of the Milky Way Mid-plane from l$=$104$.\!\!^{\circ}$75 to l$=$119$.\!\!^{\circ}$75 and b$=-$5$.\!\!^{\circ}$25 to b$=$5$.\!\!^{\circ}$25 using the $^{12}$CO, $^{13}$CO, and C$^{18}$O $J=1-0$ emission line data from the Milky Way Imaging Scroll Painting project (MWISP). We have identified 857 and 300 clouds in the $^{12}$CO and $^{13}$CO spectral cubes, respectively, using the DENDROGRAM + SCIMES algorithms. The distances of the molecular clouds are estimated and the physical properties like masses, sizes, and surface densities of the clouds are tabulated. The molecular clouds in the Perseus arm are about 30$-$50 times more massive and 4$-$6 times larger than the clouds in the Local arm. This result, however, is likely biased by distance selection effects. The surface densities of the clouds are enhanced in the Perseus arm with an average value of $\sim$100 M$_{\odot}$ pc$^{-2}$. We selected the 40 most extended ($>$0.35 arcdeg$^2$) molecular clouds from the $^{12}$CO catalog to build the H$_2$ column density probability distribution function (N-PDF). About 78\% of the N-PDFs of the selected molecular clouds are well fitted with log-normal functions with only small deviations at high-densities which correspond to star-forming regions with scales of $\sim$1-5 pc in the Local arm and $\sim$5-10 pc in the Perseus arm. About 18\% of the selected molecular clouds have power-law N-PDFs at high-densities. In these molecular clouds, the majority of the regions fitted with the power-law correspond to molecular clumps of sizes of $\sim$1 pc or filaments of widths of $\sim$1 pc.