Patterns Of The Molecular Gas Movement Will Explain The Appearance Of Stellar Cradles
Astronomers have studied the movement of molecular gas in the milky way and other nearby galaxies and found that at different scales, fluctuations in its velocity show a similar structure. While the formation of stars and planets is a local process, it is controlled by mechanisms originating at the galactic level, according to an article published in the journal Nature Astronomy.
In galaxies, gas is unevenly distributed. There are areas where the density of matter is hundreds or even thousands of times higher than average, and this is where stars are born. The appearance of clumps of matter can be influenced by various physical processes that cause the gas to move — from the galactic rotation to supernova explosions. However, it is quite complicated to determine the exact mechanisms that lead to the appearance of stellar "cradles" from a technical point of view, since first, you need to study the movement of gas at different scales, and then establish a connection with known structures and astronomical objects.
A group of astronomers led by Jonathan D. Henshaw of the Max Planck Society Institute for astronomy decided to do this work based on data from the milky way and nearby galaxy NGC 4321 obtained by the ALMA telescope (Atacama Large Millimeter/submillimeter Array). Scientists tracked how the gas moves at different scales (from 0.1 parsecs to a thousand parsecs), by changing the apparent frequency of radiation sources — this phenomenon is called the Doppler effect. The researchers programmatically analyzed millions of such measurements and visualized the interstellar medium, building a map that shows the position of the gas in two-dimensional space and its radial velocity (position-position-velocity).
As expected, the scientists registered speed fluctuations in the cold molecular gas — they can be compared to waves in the ocean. However, it turned out that these fluctuations occur everywhere and have a similar structure both on the scale of the galaxy and on the scale of individual clouds.
To better understand the nature of gas flows, Henshaw's group selected several separate regions for a more detailed study. Using statistical analysis and other methods, astronomers have identified three gas filaments in which, despite studying at different scales, equidistant "clumps" were observed, resembling beads strung on a string, whether it is the spiral arm of the galaxy or the regions of formation of individual stars.
The authors determined that the velocity fluctuations associated with equidistant structures show a characteristic periodicity, and the wavelength of these fluctuations is comparable to the voids separating equidistant dense areas. The periodic separation of giant molecular clouds and the "cradles" of individual stars is probably the result of gravitational instabilities in the parent filaments and indicates the presence of gas flows along the spiral arms of galaxies that supply new material for star formation.
At the same time, such patterns could not be detected at the intermediate scale. There, according to the researchers, the gas movement was quite chaotic.
Thanks to the movement of gas, you can learn how to form not only individual stars but also entire galaxies.