The formation and evolution of galaxies is highly dependent on the dynamicsof stars and gas, which is governed by the underlying law of gravity. Toinvestigate how the formation and evolution of galaxies takes place inMilgromian gravity (MOND), we present full hydrodynamical simulations with thePhantom of Ramses (POR) code. These are the first-ever galaxy formationsimulations done in MOND with detailed hydrodynamics, including star formation,stellar feedback, radiative transfer and supernovae. These models start fromsimplified initial conditions, in the form of isolated, rotating gas spheres inthe early Universe. These collapse and form late-type galaxies obeying severalscaling relations, which was not a priori expected. The formed galaxies have acompact bulge and a disk with exponentially decreasing surface mass densityprofiles and scale lengths consistent with observed galaxies, and verticalstellar mass distributions with distinct exponential profiles (thin and thickdisk). This work thus shows for the first time that disk galaxies withexponential profiles in both gas and stars are a generic outcome of collapsinggas clouds in MOND. These models have a slight lack of stellar angular momentumbecause of their somewhat compact stellar bulge, which is connected to thesimple initial conditions and the negligible later gas accretion. We alsoanalyse how the addition of more complex baryonic physics changes the mainresulting properties of the models and find this to be negligibly so in theMilgromian framework.

In the hierarchical structure formation model of the universe, galaxyclusters are assembled through a series of mergers. Accordingly, it is expectedthat galaxy clusters in the early universe are actively forming and dynamicallyyoung. Located at a high redshift of z=1.71, SpARCS1049+56 offers a unique lookinto the galaxy cluster formation process. This cluster has been shown to berich in cluster galaxies and to have intense star formation. Its high redshiftpushes a weak-lensing analysis beyond the regime of the optical spectrum intothat of the infrared. Equipped with deep Hubble Space Telescope Wide FieldCamera 3 UVIS and IR observations, we present a weak-lensing characterizationof SpARCS1049+56. As few IR weak-lensing studies have been performed, wediscuss the details of PSF modeling and galaxy shape measurement for an IRweak-lensing procedure and the systematics that come with the territory. Itwill be critical to understand these systematics in future weak-lensing studiesin the IR with the next generation space telescopes such as JWST, Euclid, andWFIRST. Through a careful analysis, the mass distribution of this young galaxycluster is mapped and the convergence peak is detected at a 3.3 sigma level.The weak-lensing mass of the cluster is estimated to be$3.5\pm1.2\times10^{14}\ \text{M}_\odot$ and is consistent with the massderived from a mass-richness scaling relation. This mass is extreme for acluster at such a high redshift and suggests that SpARCS1049+56 is rare in thestandard $\Lambda$CDM universe.