Credit: J. M. D. Kruijssen et al., Nature 569, 519-522 (2019). DOI: 10.1038/s41586-019-1194-3.
Also see the press release at: uni-heidelberg.de/presse/news2019/pm20190522_galaxies-as-cosmic-cauldrons.html.
Galaxies As "Cosmic Cauldrons"
Young stars heat molecular clouds and drive interstellar gas bubbles throughout galaxies
Star formation within interstellar clouds of gas and dust, so-called molecular clouds, proceeds very rapidly yet highly “inefficiently”. Most of the gas is dispersed by stellar radiation, revealing galaxies to be highly dynamic systems, like “cosmic cauldrons”, consisting of building blocks that constantly change their appearance. A team of scientists led by astrophysicist Dr Diederik Kruijssen from Heidelberg University has reached these conclusions based on new observations of the spiral galaxy NGC 300.
The movie demonstrates that molecular clouds and young stars are anti-correlated in the nearby galaxy NGC300, indicating rapid evolution between these two states. The top panels show the emission from young stars (ionised hydrogen, Hα, left) and molecular gas (carbon monoxide, CO, right), where crosses indicate emission peaks identified in each of the maps (groups of young stars in Hα and molecular clouds in CO). The bottom-left panel shows how long it takes to convert the local gas reservoir into stars, which effectively shows the ratio between the top maps. As the video plays, the spatial resolution of the images changes. At poor resolution, which could be achieved before the ALMA telescope, the bottom-left map is nearly entirely white, which shows that molecular gas and young stars are well correlated on large scales. As the resolution gradually improves and eventually reveals the exquisite detail that can now be obtained with ALMA, the colours gradually become bright red and blue, which shows that molecular clouds and young stars are anti-correlated on the small scales of individual clouds. The bottom-right panel quantifies this behaviour, by showing how the ratio between emission from molecular gas and young stars changes towards small scales. The circle and vertical line indicate the resolution ("aperture size") at which the galaxy is observed.