Understanding the transition from atomic gas to molecular gas is critical to explain the formation and evolution of molecular clouds.
![RGB compilation in the Cygnus X region covering the footprint that we surveyed; in red is the CGPS 1.4 GHz continuum (Taylor et al. 2003), green is MSX 8 µm PAH emission Schneider et al. (2006), and blue is 13CO (1-0) tracing (some of the) molecular gas (Schneider et al. 2010). Left: The numbers enclosed by a circle in black indicate the ‘DR’ continuum sources identified in 5 GHz observations by Downes & Rinehart (1966), which are mostly thermal H ii regions, except for DR3 and DR4 that make up the supernova remnant γ-Cygni. Dotted circles show the Cyg OB2 association and open clusters NGC 6910 and NGC 6913. The region at ℓ > 80◦ commonly referred to as Cyg X North and at ℓ < 80◦ (also typically at lower latitudes) as Cyg X South are also indicated. Right: Contours of velocity-integrated C273α (moment 0), drawn at [3, 5.5, 8, ...28]σ. C273α is detected from 75% of the mapped region. -- astro-ph.GA](https://i0.wp.com/astrobiology.com/wp-content/uploads/2025/01/Cold-Dark-Gas-in-Cygnus-X.png?resize=1200%2C720&ssl=1)
Understanding the transition from atomic gas to molecular gas is critical to explain the formation and evolution of molecular clouds.