Oral Presentation

MEASURING GALAXY ENVIRONMENT WITH SPECTROSCOPIC AND PHOTOMETRIC REDSHIFTS

Chuan-Chin Lai(ASIAA), Lihwai Lin(ASIAA)

Many environment measurements have been proposed and tested to quantify galaxy environments. While those environment measurements in general work well with spectroscopic redshift samples, their applications to photometric redshift surveys is uncertain. To explore whether galaxy environments are measurable in photo-z samples, we present the optimized scheme, a powerful recovery process, which can be used to measure environments from photo-z samples, and have well driven from simulation samples. Using Durham mock catalog, we first focus on how galaxy environments are affected by photo-z error. We measure 2D projected environments and compare them with 3D real-space environments by using various parameters to improve their dependence. Our results show that the 2D projected environments can correlate with 3D real-space environments as the suitable parameters used in environment measurement. Next, we construct the optimized scheme that can be used to probe the best parameters of measurement to measure the 2D projected environments that can yield the best correlation with 3D real-space environments. Finally, we evaluate the galaxy environment based on optimized scheme, investigate the correlations between galaxy color and environment, and compare the results with former study. These results show that photo-z samples can be used to measure galaxy environments, and color-density relation also can be revealed in photo-z samples with photo-z error up to 0.06(1+z). We also discuss the application of optimized scheme to the Pan-STARRS Medium Deep survey, one of the largest on-going deep imaging surveys.