Measurement of Mass Distribution of Dark Matter Using Weak Gravitational Lensing
According to the observational results from high-z supernovae and CMB, the universe almost consists of the dark matter and the dark energy.
Unfortunately, these components haven’t entirely understood yet. To understand these unknown objects, some techniques are proposed. One of these techniques is the gravitational lensing. The gravitational lensing is the effect that the shape of the background galaxy is distorted by the foreground object. We can estimate the mass
distribution of the foreground object from the distortion of the background galaxy. Even if the foreground object is the dark matter, we can estimate the mass distribution of the dark matter. In my talk,
I present the gravitational lensing of the basis of this technique.
Nature and Nurture Effects on the Formation and Evolution of Cluster Galaxies
In low-redshift clusters, most galaxies appear to be quiescent.
These galaxies tend to be elliptical or S0 galaxies, which constitute conspicuous red-sequence on the color-magnitude diagrams.
In contrast, in high-redshift proto-clusers, galaxies tend to have complicated morphologies and high star-formation rates (SFRs) of 100s $M_\odot/yr$.
Such truncation in star formation activities can be caused by “nature” effects, i.e.\ accelerated galaxy formation in dense environments, and/or by “nurture” effects, i.e.\ galaxy-galaxy interactions/mergers and gas-stripping (e.g.\ Kodama et al. 2001).
Recent works (Daddi et al 2007; Mannucci et al. 2010) have presented double (main and sub) sequences of star forming galaxies on the SFR versus gas-mass plane, and a fundamental metallicity relation (FMR) where gaseous metallicity of star forming galaxies in the SDSS are determined as a function of stellar mass and SFR, both of which describe the modes of star formation and the evolutionary stages of galaxies.
Motivated by these observational phenomena, we now aim to explore these relationships (main/sub sequenes and FMR) in clusters/proto-clusters based on near-infrared specroscopy (FMOS/MOIRCS on Subaru) and ALMA observations (Mahalo-Subaru and Gracias-ALMA projects).
By comparing these relationships in clusters with the field counterparts, we will quantify the roles of environments to shape galaxies, and thus understand the origin of environmentally dependent galaxy formation and evolution.
the determination of the masses of dark matter halos by clustering properties of sBzK galaxies
The existence of vast “dark matter halos” around luminous galaxies is strongly implied by some evidence. It is extremely difficult, however, to measure the masses of high-redshift galaxies’ dark matter halos.
One method to quantify them is to measure the amplitude of galaxy clustering, since CDM models predict a monotonic correlation that more massive halos are clustered more strongly. Measuring galaxy clustering requires a large sample from wide area.However, it is still hard to do this at z~2, where BzK color selection can allow us to accumulate larger samples, due to a lack of combination of wide optical and NIR data. I will show our challenge to overcome this difficulty.