The Study Of Neutral Hydrogen In Dwarf Galaxies

The cold dark matter model is known as the "standard model" in the cosmology,and it is perfectly validated in the large scale range.In the small scale,however,the model has three main problems:(1)missing satellites problem,the number of substructures in the simulated Milky Way(MW)mass dark matter haloes significantly larger than that of the known luminous MW satellites.(2)too big too fail problem,the count of sub-haloes with Vmax>25km/s predicted in MW-mass dark matter halos greatly exceeds that of the observations.(3)the thin planar distribution of the classical satellites,the brightness satellites of the MW are distributed in a plane that is roughly perpendicular to MW disk,while roughly half of M31's satellite galaxies belong to a vast,thin co-rotating plane.In order to solve the first two problems,one of the methods is to enhance the detection of dwarf galaxies.FAST telescope is the largest single dish in the world,which enhances the human's ability to detect dwarf galaxies.In this thesis,we study the detectability of satellites in the local group by using the FAST telescope.Our mock survey is based an advanced high-resolution numerical simulation,APOSTLE-HR4.We find that the satellites in the local group with HI mass larger than 105 M?can be detected by the FAST if the integration time is larger than 40 minutes.At present,the dependence of the dwarf galaxies on the environment and the formation of the dwarf galaxies are still unclear,the second topic of this thesis is to study HI distribution of the dwarf galaxies by using both the SDSS-DR7 and ALFALFA survey catalogues.We find that most dwarf galaxies with the HI observations are the field galaxies.In the group,most dwarf galaxies are satellites,and only a small number of them are the central galaxies in the group.In each group,the number of dwarf galaxies with observation of the neutral hydrogen is generally no more than two.We further study the neutral hydrogen properties of dwarf galaxies in different colors.It is found that the average neutral hydrogen content of the blue dwarf galaxies is larger than that the red ones.The neutral hydrogen distribution of the reddwarf galaxies is closer to the center of the group than the blue ones.The studies of this thesis can be helpful to solve the problems of the LCDM model in small scale and the formation of dwarf galaxies.