Refracting into Ultra Diffuse Galaxy NGC 1052-DF2 by Passing near the
  Center of NGC 1052
  The recent observation of the ultra-diffuse galaxy NGC 1052-DF2 shows a
galaxy may lack dark matter. Usually dark matter is much more abundant than
stellar in galaxy environment. This dark matter to baryon mass ratio is
generally larger than the cosmological ratio of about five, since a significant
part of baryon is diffused in the form of intergalactic medium. How to achieve
such a low dark matter to baryon mass ratio is a challenge to the standard
galaxy formation mechanism. Here we show that such a low ratio can be a natural
consequence if the NGC 1052-DF2 had experienced a single passage within a few
kpcs to the center of galaxy NGC 1052. The tidal effect of NGC 1052 in the
encounter will heat the NGC 1052-DF2 up, stretch the previous dwarf galaxy
significantly into its current size. The relative lacking of dark matter in the
observed region is a natural consequence of the dark matter extended
distribution and relatively less concentration in the corresponding central
region before encounter, together with a systematic underestimation of the
trace mass estimator method during relaxation after encounter. The observed
flat distribution of the ultra-diffuse galaxy can be reproduced. Our results
shows no need of introducing any new physical mechanism.
