Missing Baryons and the Warm-Hot Intergalactic Medium
Fabrizio Nicastro,*1,2
Smita Mathur,3
Martin Elvis1
Stars and gas in galaxies, hot intracluster medium, and intergalactic
photo-ionized gas make up at most half of the baryons that are
expected to be present in the universe. The majority of baryons
are still missing and are expected to be hidden in a web of
warm-hot intergalactic medium. This matter was shock-heated
during the collapse of density perturbations that led to the
formation of the relaxed structures that we see today. Finding
the missing baryons and thereby producing a complete inventory
of possibly the only detectable component of the energy-mass
budget of the universe is crucial to validate or invalidate
our standard cosmological model.
2 Osservatorio Astronomico di Roma–Istituto Nazionale di Astrofísíca, Rome I-00040, Italy.
3 Ohio State University, Columbus, OH 43210, USA.
* To whom correspondence should be addressed. E-mail: fnicastro{at}cfa.harvard.edu
