摘要：Context. Filamentary structures are common morphological features of the
cold, molecular interstellar medium (ISM). Recent studies have discovered massive,
hundred-parsec-scale filaments that may be connected to the large-scale, Galactic spiral
arm structure. Addressing the nature of these giant molecular filaments (GMFs) requires a
census of their occurrence and properties.
Aims. We perform a systematic search of GMFs in the fourth Galactic
quadrant and determine their basic physical properties.
Methods. We identify GMFs based on their dust extinction signatures in
the near- and mid-infrared and the velocity structure probed by 13CO line emission. We use the
13CO line
emission and ATLASGAL dust emission data to estimate the total and dense gas masses of the
GMFs. We combine our sample with an earlier sample from literature and study the Galactic
environment of the GMFs.
Results. We identify nine GMFs in the fourth Galactic quadrant: six in
the Centaurus spiral arm and three in inter-arm regions. Combining this sample with an
earlier study using the same identification criteria in the first Galactic quadrant
results in 16 GMFs, nine of which are located within spiral arms. The GMFs have sizes of
80–160 pc and 13CO-derived masses between 5−90 ×
104M⊙. Their dense gas mass
fractions are between 1.5–37%,
which is higher in the GMFs connected to spiral arms. We also compare the different
GMF-identification methods and find that emission and extinction-based techniques overlap
only partially, thereby highlighting the need to use both to achieve a complete
census.
