The universe is believed to contain a huge amount of dark matter. Dark matter contributes to about 80％ of the material mass of the universe; however, attempts to detect the dark matter directly with current telescopes are still unsuccessful even though the existence of dark matter can be deduced from its gravitational influence on the movement of ordinary matter. Evidences for dark matter in spiral galaxies were found from the studies of rotation curves and other kinematic information. Observations suggested that a huge a mount of invisible (missing) mass is required in order to explain the observed rotation curves in most galaxies. Previous studies showed that dark matter is a common feature in galaxies.

 

In contrast to the missing mass problem in normal galaxies, luminous infrared galaxies (LIRGs) were found to contain too much molecular mass. LIRGs were usually merging galaxies and found to contain a huge amount of molecular mass in the central regions of the galaxies; however, the estimated molecular masses are usually too huge to be reconciled with the observed dynamical masses. The inconsistency is usually believed due to the error of the CO-luminosity-to-H2-mass conversion factor for the LIRGs; the standard value of the conversion factor, which was derived from the Galaxy, might not be applicable in the LIRGs. However, since LIRGs or merging galaxies should also be in the processes of merging of dark halos according to the hierarchical scenario of galaxy formation, it is very interesting to investigate what is the distribution of dark matter in the LIRGs.

In this project, we would like to investigate the dark matter distribution in LIRGs using ALMA archival data. In this program, students would learn techniques of data reduction and analysis for ALMA as well as astronomy and astrophysics about dark matter and merging galaxies.