World's largest radio telescopes reveal mysterious star formation at galaxy edges

Using data from the world's largest radio telescopes, astronomers have revealed mysterious star formation at the far edge of the galaxy M83 - one of the brightest spiral galaxies in the night sky.

Also known as the Southern Pinwheel Galaxy, M83 is located 15 million light-years away from Earth. Research on the far edge of this galaxy has revealed unusual star formation in an extreme environment.

This research discovered 23 molecular clouds that exhibit a distinct type of star formation. Unlike typical molecular clouds, the large bodies of these clouds were not visible - only their star-forming dense cores were observed. This discovery provides an essential clue to understanding the physical processes involved in star formation.

"The star formation at galaxy edges has been a nagging mystery since their discovery by the NASA GALEX satellite 18 years ago. David Thilker of Johns Hopkins University, who originally discovered the star formation activity occurring in the outskirts of M83 and other galaxies, commented, "It has been gratifying to see the search for dense clouds associated with the outer disk finally come to fruition, revealing a characteristically different observational fingerprint for the molecular clouds," said astronomer Jin Koda of Stony Brook University, who led this research, "Previous searches for molecular clouds in this environment turned out unsuccessful.

The discovery of these molecular clouds has revealed a connection to a vast reservoir of diffuse atomic gas, another significant finding of this research. Usually, atomic gas condenses into dense molecular clouds, where even more condensed core regions develop and eventually form stars. This process occurs even at the edges of galaxies, but the transformation of atomic gas to molecular clouds was not apparent, the mystery behind which is yet to be resolved.

For this discovery, the researchers used data from the Atacama Large Millimeter/submillimeter Array (ALMA), the Karl G. Jansky Very Large Array (VLA) and the Green Bank Telescope (GBT) from NRAO, along with the National Astronomical Observatory of Japan's (NAOJ) Subaru Telescope and the NASA Galaxy Evolution Explorer (GALEX).