Warm-hot envelope of gas at z=3 in formation.
Spiral galaxies are embedded in gaseous halos which connect intergalactic medium (IGM) to the star-forming disks of galaxies. These gaseous halos consist of multi-phase medium that can be observed in absorption and emission lines or as an excessive X-ray emission with respect to the background. We used Nbody/SPH cosmological simulations of Milky Way-sized galaxies to show that the properties of simulated halos, such as electron density profiles, X-ray luminosities, or coronal density necessary to ram-pressure strip Milky Way dwarfs of their gas, are compatible with those of the Milky Way and thus are predictions, for which these simulations were not calibrated (see Paper I).
Moreover, we identified a common feature in these galaxies, hot coronae of gas confined to within 140 kpc. Variations in setups such as location in the cosmic web (dense, sparse environment) or strengths and types of feedback implementation, although through different evolutionary pathways, lead to the same end-state of a galaxy. In Paper II (in prep.), we explain how such coronae form.
Merger of seeds of the future galaxies in action.
In the standard theory of disk galaxy formation the sizes of galaxies an be easily explained if baryons retain their specific angular momentum, initially resulting from tidal torques, as they collapse into the halo centers. We use high-resolution zoom-in cosmological simulations of late-type galaxies in order to understand the evolutionary tracks of gas and stars on the j/M* diagram, as well as how closely the angular momentum of baryons is coupled with that of dark matter.
Cold gas on larger scales in the Universe.
Observed baryon fraction of galaxies falls short of the cosmic baryon fraction, which could be explained by ejection of baryons in feedback processes and/or the presence of large reservoir of baryons in a difficult-to-detect form. For example, warmhot gas (10^5-6) within the galaxies or warm-hot intergalactic medium in the cosmic web (WHIM) would be high-energy and diluted, hence difficult to detect with the current instrumentation. In this project, we are interested in how baryons are distributed in the Universe. Therefore we study low-mass systems such as Milky Way analogues in low-density environments and loose groups, as well as high-mass systems (5x10^12Msol). We investigate the relevance of feedback processes at those scales.