Astronomers have detected a previously unknown giant molecular cloud (GMC) at the midpoint of the Galactic Bar Dust Lanes using spectral line observations taken with the Green Bank Telescope (GBT).
Stretching nearly 200 light-years across and weighing approximately 160,000 times the mass of the Sun, the new GMC has received the designation of M4.7–0.8.
Molecular clouds, made mostly of hydrogen, are vast collections of interstellar gas and dust left over from galaxy formation.
Those exceeding 100,000 solar masses are classified as giant molecular clouds.
Spanning 15 to 600 light-years, GMCs represent the coldest and most densely packed regions of the interstellar medium, serving as gas reservoirs where most star formation takes place.
New Galactic Discovery
A team of astronomers at the National Radio Astronomy Observatory (NRAO) discovered the cloud at the midpoint of a dust lane within the Milky Way’s central bar, approximately 23,000 light-years away.
“We report the detection of a previously unknown giant molecular cloud located at the midpoint of the near-side Galactic bar dust lanes (M4.7-0.8),” the researchers, led by Natalie O. Butterfield, wrote in a paper published on March 18.
“In this publication we present 25 GHz radio observations of dense gas that is associated with material accreting into the Galactic center,” they added.
These dust lanes are vital channels that transport material from the galaxy’s disk to the center of the Milky Way, where it gathers into dense, ring-like structures, fueling intense star formation.
According to the astronomers, the newly discovered GMC spans approximately 195 light-years in Galactic longitude and extends about 65 light-years in Galactic latitude.
The cold dust temperature of the M4.7-0.8 was estimated to be at a level of 20 K.
Distinct features within the cloud
They also found two distinct features in the cloud, which they termed “Nexus” and “Filament.”
The Nexus aligns with the brightest carbon monoxide (CO) emission and appears to be associated with the intersection of the dust continuum and CO emission.
On the contrary, Filament is a narrow dust continuum structure that extends from the Nexus and showcases a filamentary morphology.
The researchers have also detected two sites —Knot B and Knot E — of possible star formation in M4.7-0.8.
The researchers observed that Knot E could likely be a free-floating evaporating gas globule with a dense cometary-like structure, which requires further investigation.
The study also found that the new cloud also includes a shell-like structure, which possibly contains a brighter rim in the ammonia emission and has a cavity towards its center.
Studying molecular clouds is crucial to understanding the fundamental processes that drive star formation and galaxy evolution.
By analyzing their composition, structure, and dynamics, astronomers can gain insights into how stars form, how galaxies evolve over time, and how different environmental factors influence star-forming activity.
Moreover, GMCs play an important role in the galactic ecosystem, influencing the interstellar medium through processes like supernova feedback and turbulence.
Gaining insight into the physical properties of the molecular clouds help refine star formation models and improve predictions about the life cycle of galaxies.
The findings have been published in the arXiv preprint server.