Astronomers have made groundbreaking discoveries about the circumgalactic medium (CGM), a diffuse gaseous halo surrounding galaxies, that are shedding new light on galaxy evolution. The CGM plays a critical role in replenishing gas and metals for star formation and recording ejected material from stellar processes.
Using data from the Hubble Space Telescope and the Cosmic Origins Spectrograph, researchers have analyzed the CGM around various galaxies, including star-forming galaxies with metal-enriched tracers like magnesium II. The study reveals that these galaxies exhibit stronger signatures of metal enrichment along their minor axes, likely driven by galactic winds.
The warm-phase CGM, characterized by temperatures around 300,000 Kelvin, shows a striking dichotomy in oxygen VI content, with star-forming galaxies displaying high levels of this ion and passive ones showing almost none. This contrast highlights the relationship between star formation and the ionization state of the CGM.
A new survey, CIViL, has more than doubled existing observations for low-redshift galaxies, providing crucial near-ultraviolet data that bridges gaps in prior research. The survey reveals significant differences in carbon detection rates between star-forming and passive galaxies, with detection fractions standing at 72% and 23%, respectively.
These findings emphasize the CGM’s role as both a contributor to and a record of galaxy evolution. The enriched CGM in star-forming galaxies reflects ongoing feedback processes, while the sparse CGM in passive galaxies underscores the diminishing feedback in their absence.
The interplay between the CGM and star formation influences broader cosmic cycles, with materials eventually recycling back into galaxies, sustaining future star formation. As research continues, questions about the CGM’s ionization mechanisms and interactions with other galactic components persist, but the CIViL survey represents a step forward in filling observational gaps and advancing our understanding of this crucial component of galaxy evolution.
Source: https://www.thebrighterside.news/post/astronomers-discover-interstellar-processes-that-drive-galactic-evolution