The Role of Major Galaxy Interactions in Galaxy Evolution Since Redshift z ~ 1

• Main Authors: Lihwai Lin, 林俐暉
• Other Authors: 闕志鴻
• Format: Others
• Language: en_US
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/18631810631842021984

博士 === 國立臺灣大學 === 物理研究所 === 94 === We present the close, kinematic pair fraction and merger rate up to redshift $z sim 1.2$ for a large sample of galaxies observed by the DEEP2 Redshift Survey. The effect of the galaxy interactions/mergers has also been addressed by studying the infrared luminosity to the stellar mass ratios speir for $sim 100$ galaxies using images taken by the $Hubble$ $Space$ $Telescope$ Advanced Camera for Surveys in $V$ and $I$ and $Spitzer$ MIPS in 24m. Assuming a mild luminosity evolution, the number of companions per luminous galaxy is found to evolve as $(1+z)^{m}$, with $m= 0.51pm0.28$. Our results imply that only $9\%$ of present-day $L^{*}$ galaxies have undergone major mergers since $zsim1.2$ and that the average major merger rate is about $4 imes 10^{-4}$ $h^{3}$ Mpc$^{-3}$ Gyr$^{-1}$ for $z sim 0.5 - 1.2$. When dividing the galaxies into blue and red colors, the evolution index $m$ remains similar for blue-blue pairs while $m$ becomes negative for red galaxies. The evolution trend for different types of galaxies can be explained by the change of galaxy number density and clustering properties over cosmic time. At fixed stellar mass (sm) the median infrared luminosity (lir) among merging galaxies and close pairs of blue galaxies is twice (1.9$pm$0.4) that of control pairs drawn from isolated blue galaxies. Enhancement declines with galaxy separation, being strongest in close pairs and mergers and weaker in wide pairs compared to the control sample. At $overline{z} sim 0.9$, $7.1pm4.3\%$ of massive interacting galaxies (sm $>$ $2 imes10^{10} M_{odot}$) are found to be ULIRGs, compared to $2.6pm0.7\%$ in the control sample. The large spread of speir among interacting galaxies suggests that this enhancement may depend on the merger stage as well as other as yet unidentified factors (e.g., galaxy structure, mass ratio, orbital characteristics, presence of AGN or bar). The contribution of interacting systems to the total IR luminosity density is moderate ($leq 36\%$).