Eggs of stars sleeping in Cygnus region, the largest cradle in Milky Way.
Understanding the process of stellar cluster formation from molecular clouds is one of the most crucial issues in astrophysics. The Cygnus giant molecular cloud complex, which is known to be one of the most active star-forming regions in the Milky Way, is located at the distance of approximately 5000 light-years from the solar system. The early observational studies revealed that there is a large amount of molecular gas more than one million solar masses, and a lot of young stellar clusters are currently forming at the innermost part of the cloud. The Cygnus region is thus an ideal laboratory to investigate the formation process of stellar clusters. Parental high-density clumps are supposed to transform into stellar clusters, and the clumps are often observed by molecular line emission, for example, C18O, which is a rare isotope of carbon monoxide at a wavelength of 2.7 mm. However, the intensity of the C18O emission is very weak, so that it was challenging to observe toward across the Cygnus region extensively. FOREST, an instrument installed on the Nobeyama 45 m radio telescope in 2014, enables us to perform unprecedented surveys with an excellent sensitivity to explore high-density clumps in the Cygnus region. The research group has successfully found 174 high-density clumps: "the eggs" of stars or stellar clusters . Most of the clumps were gravitationally bound well, and they were considered to evolve into protostars or proto-clusters. The mass spectrum, the number distribution of the clumps, is also confirmed to be similar to that of the newly born stars in the Milky Way. These results support the hypothesis that star formation activities in giant molecular cloud complexes, such as the Cygnus region, produce most of the stars in galaxies. These observation results were published as Takekoshi et al. “Nobeyama 45 m Cygnus-X CO Survey. II. Physical Properties of C18O Clumps,” in the Astrophysical Journal on October 1st, 2019.
Figure:The radio image of the Cygnus-X molecular cloud complex observed by the Nobeyama 45 m telescope.
The red, green, and blue color shows 12CO, 13CO, and C18O molecular line emission, respectively.
Related Links Nobeyama 45-m Radio Telescope Web Page Cygnus-X Survey School of Science,The University of Tokyo Press Release Eggs of stars sleeping in Cygnus region, the largest cradle in Milky Way.