Using high resolution SPH simulations in a fully cosmological \Lambda CDM context we study the formation of a bright disk dominated galaxy that originates from a “ wet ” major merger at z = 0.8 .
The progenitors of the disk galaxy are themselves disk galaxies that formed from early major mergers between galaxies with blue colors .
A substantial thin stellar disk grows rapidly following the last major merger and the present day properties of the final remnant are typical of early type spiral galaxies , with an i band B/D \sim 0.65 , a disk scale length of 7.2 kpc , g - r = 0.5 mag , an HI line width ( W _ { 20 } /2 ) of 238 km/sec and total magnitude i = -22.4 .
The key ingredients for the formation of a dominant stellar disk component after a major merger are : i ) substantial and rapid accretion of gas through cold flows followed at late times by cooling of gas from the hot phase , ii ) supernova feedback that is able to partially suppress star formation during mergers and iii ) relative fading of the spheroidal component .
The gas fraction of the progenitors ’ disks does not exceed 25 % at z < 3 , emphasizing that the continuous supply of gas from the local environment plays a major role in the regrowth of disks and in keeping the galaxies blue .
The results of this simulation alleviate the problem posed for the existence of disk galaxies by the high likelihood of interactions and mergers for galaxy sized halos at relatively low z .