Star-forming content of the giant molecular filaments in the Milky Way
  Observations have discovered numerous giant molecular filaments (GMFs) in the
Milky Way. However, their role in the Galactic star formation and Galaxy-scale
evolution of dense gas is still unknown. We investigate systematically the
star-forming content of all currently known GMFs. This allows us to estimate
the star formation rates (SFRs) of the GMFs and to establish relationships
between the SFRs and the GMF properties. We identify and classify the young
stellar object (YSO) population of each GMF using multi-wavelength photometry
from near- to far-infrared. We estimate the total SFRs assuming a universal and
fully sampled initial mass function and luminosity function. We uniformly
estimate the physical properties of 57 GMFs. The GMFs show correlations between
the 13CO line width, mass, and size, similar to Larson's relations. We identify
36 394 infrared excess sources in 57 GMFs and obtain SFRs for 46 GMFs. The
median SFR surface density (Sigma_SFR) and star formation efficiency (SFE) of
GMFs are 0.62 Msun Myr-1 pc-2 and 1%, similar to the nearby star-forming
clouds. The star formation rate per free-fall time of GMFs is between
0.002-0.05 with the median value of 0.02. We also find a strong correlation
between SFR and dense gas mass that is defined as gas mass above a visual
extinction of 7 mag, which suggests that the SFRs of the GMFs scale similarly
with dense gas as those of nearby molecular clouds. We also find a strong
correlation between the mean SFR per unit length and dense gas mass per unit
length. The origin of this scaling remains unknown, calling for further studies
that can link the structure of GMFs to their SF activity and explore the
differences between GMFs and other molecular clouds
