Sanskriti Das and Salome Mtchedlidze

From the calendar

The hot circumgalactic medium (CGM), a reservoir of missing baryons, metals, and energy, plays a key role in our understanding of galaxy evolution. However, extraordinary observational challenges make the hot CGM one of the least understood components of galaxies. Studying the hot CGM was not the objective of current X-ray or mm facilities during the design phase. However, as an excellent byproduct, observing the hot CGM has emerged as a promising field over the last two decades, coming at the forefront of priority science goals for the current and upcoming decades.

I will discuss three snippets of our recent efforts to detect and characterize the hot CGM: 1) X-raying the Milky Way: Investigating thermal and chemical anomalies; 2) Is CGM detectable? Conducting deep searches in individual external galaxies using X-ray; and 3) Test for self-similarity: stacking thousands of galaxies in mm (Sunyaev-Zeldovich Effect). I will highlight how our findings provide insights into the impact of galactic feedback on the hot CGM, establish our confidence in leveraging current telescopes to inform theoretical simulations, and set a benchmark for designing experiments with next-generation X-ray and mm facilities.

The magnetisaton of our universe on galaxy and galaxy cluster scales, and in the recent years revealed on filamentary scales as well, raises interest in understanding its origin. The blazar spectra observations provide an intriguing possibility of the existence of magnetic fields in cosmic voids. This motivates us not only to explore their origin but also to predict their structure on these vast scales, especially for the upcoming radio observations with the Square Kilometer Array. If large-scale magnetism originates from fields generated in the late Universe — during reionization and structure formation — such fields could influence the magnetisation and possibly the evolution of the intracluster and intergalactic medium. On the other hand, if magnetic fields are primordial, generated in the pre-recombination Universe, they can naturally permeate the entire Universe and leave imprints on various cosmological phenomena (e.g., on the Cosmic Microwave Background and matter power spectra, propagation of high-energy gamma rays, relic gravitational waves, etc). In this talk, I will first briefly summarise current observational results confirming the existence of magnetic fields on large scales of the Universe, along with the physics associated to cosmic magnetism (including their signatures). I will then present results findings from our study where we explored the evolution of primordial magnetic fields with different coherence scales on cosmic scales. Finally, I will discuss implications of our findings for Rotation Measure (one of the powerful probes of magnetic fields on galaxy cluster scaless and in the intergalactic medium) analysis.