Characterizing Interacting Galaxies out to z 0.8 Using CAS and Visual Classification
Miller, Sarah; Jogee, S.; Penner, K.; Conselice, C.;Bell, E. F.; Zheng, X. Z.; Papovich, C.;Skelton, R. E.; Somerville, R. S.; Robaina, A. R.;Rix, H. W.; Barazza, F. D.; Barden, M.; Borch, A.;Caldwell, J. A. R.; Haeussler, B.; Heymans, C.;Jahnke, K.; McIntosh, D. H.; Meisenheimer, K.;Peng, C. Y.; Sanchez, S. F.; Wisotzki, L.; Wolf, C.. Characterizing Interacting Galaxies out to z 0.8 Using CAS and Visual Classification. American Astronomical Society, AAS Meeting #211, #52.05; Bulletin of the American Astronomical Society. 2007, Vol. Vol. 39, p.820, p. -2007.
The recent advent of large space-based surveys with thousands of galaxies, such as GEMS, AEGIS, COSMOS has led to different methods for identifying interacting and merging galaxies, such as detailed visual classifications and quantitative non-parametric codes, such as CAS. However detailed assessments of the results from these methods have been greatly lacking. In this study, we analyze HST ACS images of 4000 galaxies from the GEMS survey at redshifts z 0.24 to 0.80, and identify normal undisturbed galaxies and strongly disturbed interacting/merging systems using two methods: the CAS system of concentration (C), asymmetry (A), and clumpiness (S) parameters, and visual classification. We investigate the effectiveness of the CAS criteria in the A-S and C-A planes in identifying visually-classified normal versus strongly distorted/interacting systems. We examine how the CAS clumpiness and asymmetry parameters are related to the star formation rate (SFR) of galaxies in both normal and disturbed galaxies. We compare the average SFR and SFR density as a function of redshift between normal and strongly disturbed galaxies using CAS, and compare the results to visual classifications. In particular, we explore what fraction of the total SFR density over z 0.24 to 0.80 originates from strongly disturbed interacting galaxies. We acknowledge support from NASA LTSA grant NAG5-13063, NSF grant AST-0607748, and HST grants G0-9500, GO-10395 and GO-10861.
The recent advent of large space-based surveys with thousands of galaxies, such as GEMS, AEGIS, COSMOS has led to different methods for identifying interacting and merging galaxies, such as detailed visual classifications and quantitative non-parametric codes, such as CAS. However detailed assessments of the results from these methods have been greatly lacking. In this study, we analyze HST ACS images of 4000 galaxies from the GEMS survey at redshifts z 0.24 to 0.80, and identify normal undisturbed galaxies and strongly disturbed interacting/merging systems using two methods: the CAS system of concentration (C), asymmetry (A), and clumpiness (S) parameters, and visual classification. We investigate the effectiveness of the CAS criteria in the A-S and C-A planes in identifying visually-classified normal versus strongly distorted/interacting systems. We examine how the CAS clumpiness and asymmetry parameters are related to the star formation rate (SFR) of galaxies in both normal and disturbed galaxies. We compare the average SFR and SFR density as a function of redshift between normal and strongly disturbed galaxies using CAS, and compare the results to visual classifications. In particular, we explore what fraction of the total SFR density over z 0.24 to 0.80 originates from strongly disturbed interacting galaxies. We acknowledge support from NASA LTSA grant NAG5-13063, NSF grant AST-0607748, and HST grants G0-9500, GO-10395 and GO-10861.