import yt
from yt.units import kpc
ds = yt.load('IsolatedGalaxy/galaxy0030/galaxy0030')
my_galaxy = ds.disk(ds.domain_center, [0.0, 0.0, 1.0], 10*kpc, 3*kpc)
p = yt.ParticlePlot(my_galaxy, 'particle_position_x', 'particle_position_y')

p.set_ylog(False)
p.set_xlog(False)
p.set_line_property('markersize', 2)

p.set_unit('particle_position_x', 'kpc')
p.set_xlim(485, 515)

p.set_unit('particle_position_y', 'kpc')
p.set_ylim(485, 515)

p.show()