A large Amount of Hot Gas Permeates the Halos of Local Galaxies

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Speaker :  
Dr. Fabrizio Nicastro (INAF & Rome Observatory, Italy)
Location :  
2nd Floor Seminar Room & Online
Date :  

Time : 

Abstract :

The number of baryons hosted in the disks of galaxies is lower than expected based on the mass of their dark-matter halos and the fraction of baryon-to-total matter in the universe, giving rise to the so called galaxy missing-baryon problem. The presence of cool circum-galactic matter gravitationally bound to the galaxy up to distances of at least ten times the size of the galaxy’s disk, mitigates the problem but is far from being sufficient for its solution. In this contribution we show that X-ray spectroscopic data of known cool Circum-Galactic Lyman-Limit Systems, reveal the presence of a large amount of hot gas in the halos of local galaxies, possibly co-existing with, and pressure-confining, the cool-CGM. Main tracers of this hot medium are highly ionized light elements that only retain one or two electrons and that are only visible in the X-rays. The temperatures of this hot CGM component  is consistent with the galaxies’ virial temperatures and its mass is sufficient to close the galaxy’s baryon census.