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My research interest:
Galaxies collisions in both standard dynamics and modified Newtonian dynamics (MOND);
Dynamics of GCs and dwarf galaxies;
Dynamics of galaxies from cosmologically simulated galaxies.Current projects:
1. Formation of collisional ring galaxies;
2. The interaction of star clusters and their host galaxy;
3. Analysis of cosmological simulated galaxies.
Recent projects:
1. Gas expulsion in Modified Newtonian Dynamics (MOND, Wu & Kroupa 2018, 2019):
We study the evolution of star clusters located in the outer regions of a galaxy undergoing a sudden mass loss through gas expulsion in the framework of Newtonian dynamics and of Milgromian dynamics (MOND) by means of N-body simulations. We find that, for a given SFE, the star clusters that survive in MOND can bind a larger fraction of mass compared to those of the Newtonian dynamics. Moreover, the more diffuse the embedded cluster is, the less substantial the size expansion of the final star cluster is. Gas expulsion can explain the observed line-of-sight (LoS) velocity dispersion profile of NGC 2419 in Newtonian dynamics. However, gas expulsion alone is unlikely the physical mechanism for the observed velocity dispersion profile of NGC 2419 in MOND.
2. Kinematics of lopsided cluster galaxies (Wu et al. 2017):
Left panel: Axisymmetric galaxies are not stable in Milgrom's dynamics (MOND). The instability originates from the box orbits and the non-classified orbits with low angular momentum. Right palel: The offsets of nuclei in dwarf elliptical galaxies insided the Virgo cluster. The centroids' offsets are predicted in cluster galaxies in MOND.
3. The mass-discrepancy-to-acceleration (MDA) relation for the observed galaxies an for the cosmological simulated galaxies:
The MDA data emerging in cold/warm dark matter (C/WDM) cosmological simulations disagree significantly with the tight MDA correlation of the observed galaxies, while such correlation is a natural prediction in Milgrom's modified gravity.
Upper panel: The observed (black dots) and cosmologically simulated (colour areas and green curve) mass discrepancy of galaxies as a function of Newtonian gravity. The red and orange curves show the predictions of mass discrepancy in Milgromian dynamics with different mu functions. Middle panel: The difference of mass discrepancy between observed data and models. Lower panel: Relation between dynamical gravity and Newtonian gravity. (Wu and Kroupa 2015)
4. Mass and angular momentum in ETGs simulated from cosmological mergers:
Upper panels:Temporally smoothed mean LOS velocity maps for the stellar components of the same model galaxies. Middle panels: Maps of temporally smoothed velocity dispersion, sigma. Bottom panels: Maps of ratio v/sigma. The surface densities of the stellar components are overplotted on these maps; contour levels are 10^7.0 , 10^7.5, 10^8.0 , 10^8.5 , 10^9.0 Msun kpc^-2 h. The three model galaxies chosen here are: a slow rotator (M0125), a slow rotator with a peak of Lambda(R) around 2 Re (M1017), and a fast rotator with increasing Lambda(R) up to 2 Re (M0300). (Wu et. al. 2014)