CO~($J=1-0$) Observations toward Filamentary Molecular Clouds in the Galactic Region with $l = [169\arcdeg.75, 174\arcdeg.75], b = [-0\arcdeg.75, 0\arcdeg.5]$

TL;DR

This study uses CO isotopologue observations to analyze filamentary molecular clouds in a specific Galactic region, revealing their physical properties, gravitational stability, and ongoing star formation activities.

Contribution

First detailed characterization of filamentary structures and their star-forming potential in this Galactic region using CO isotopologue data.

Findings

Identified five molecular clouds with filamentary structures.

Most filaments are gravitationally bound and supported by turbulence.

Detected ongoing star formation activity within some filaments.

Abstract

We present observations of the CO isotopologues ($^{12}$CO, $^{13}$CO, and C$^{18}$O) toward the Galactic region with $169\arcdeg.75 \leqslant l \leqslant 174\arcdeg.75$ and $-0\arcdeg.75 \leqslant b \leqslant 0\arcdeg.5$, using the Purple Mountain Observatory 13.7~m millimeter-wavelength telescope. Based on the $^{13}$CO~($J = 1-0$) data, we find five molecular clouds within the velocity range between $-$25 and 8~km~s$^{-1}$ that are all characterized by conspicuous filamentary structures. We have identified eight filaments with a length of 6.38--28.45~pc, a mean H$_2$ column density of 0.70$\times$10$^{21}$--6.53$\times$10$^{21}$~cm$^{-2}$, and a line mass of 20.24--161.91~$M_\sun$ pc$^{-1}$, assuming a distance of $\sim$1.7~kpc. Gaussian fittings to the inner parts of the radial density profiles lead to a mean FWHM width of 1.13$\pm$0.01~pc. The velocity structures of most filaments present continuous distributions with slight velocity gradients. We find that turbulence is the dominant internal pressure to support the fragmentation of filaments instead of thermal pressure. Most filaments have virial parameters smaller than 2; thus, they are gravitationally bound. Four filaments have an LTE line mass close to the virial line mass. We further extract dense clumps using the $^{13}$CO data and find that 64$\%$ of the clumps are associated with the filaments. According to the complementary IR data, most filaments have associated Class~II young stellar objects. Class~I objects are mainly found to be located in the filaments with a virial parameter close to 1. Within two virialized filaments, $^{12}$CO outflows have been detected, indicating ongoing star-forming activity therein.