On the evolution of observable properties of 1:1 merger remnants
Inchan Ji (Yonsei University)
The evolution of star formation rates and observable properties of equal-mass disk mergers were investigated using numerical simulations. We perform N-body/hydrodynamic simulations and all of which include cooling of gas, star formation, and supernova feedback. We study twelve different merger simulations considering various initial orbital configurations and morphological properties of progenitor galaxy. We have calculated the observable properties of merger remnants i.e., colors and magnitudes convolved with dust attenuation. Then we compare our results with observational data from the Sloan Digital Sky Survey (SDSS). We show that u − r colors of merger remnants coevolve with star formation rates. u − r colors of merger remnants evolve differently between the merger simulations without considering dust attenuation. However, dust attenuation hinders the clear differences especially during starburst. We estimate the post-merger tim e, the moment when post-merger features of merger remnants disappear. We compare the post-merger times between the simulations after synthesizing mock images using the SDSS r band. The post-merger time is useful to understand morphological transformation of galaxy merger. We found that the post-merger features involve a small fraction of stars and the post-merger time depends on how galaxies interact. The post-merger time is, on average, ∼ 2 times the final coalescence time for a shallow surface bright limit, i.e. μ ∼ 25 mag per square arcsec. For a deeper surface brightness limit, i.e. μ ∼ 28 mag per square arcsec, however, the post-merger time is by a factor of ∼ 2.3 longer than in the shallow one, which is the reason why detecting merger features by using shallow surveys were difficult in the past.