Open AccessGalaxy formation in pre‐heated intergalactic media
Author(s) -
Mo H. J.,
Mao Shude
Publication year - 2002
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2002.05416.x
Subject(s) - physics , astrophysics , protogalaxy , galaxy merger , dark galaxy , interacting galaxy , astronomy , galaxy formation and evolution , lenticular galaxy , galaxy , type cd galaxy
We outline a scenario of galaxy formation in which the gas in galaxy‐forming regions was pre‐heated to high entropy by vigorous energy feedback associated with the formation of stars in old ellipticals and bulges and with active galactic nuclei activity. Such pre‐heating probably occurred at redshifts of z ∼2–3 , and can produce the entropy excess observed today in low‐mass clusters of galaxies without destroying the bulk of the Ly α forest. Subsequent galaxy formation is affected by the pre‐heating, because the gas no longer follows the dark matter on galaxy scales. The hot gas around galaxy haloes has very shallow profiles and emits only weakly in the X‐ray range. Cooling in a pre‐heated halo is not inside–out, because the cooling efficiency does not change significantly with radius. Only part of the gas in a protogalaxy region can cool and be accreted into the final galaxy halo by the present time. The accreted gas is probably in diffuse clouds and so does not lose angular momentum to the dark matter. Cluster ellipticals are produced by mergers of stellar systems formed prior to the pre‐heating, while large galaxy discs form in low‐density environments where gas accretion can continue to the present time.