2003/12/01 by Tomotsugu Goto, Chisato Yamauchi, Yutaka Fujita +5 · 1 citation
Physics and Astronomy · #astro-ph
paper · pdf · doi:10.1046/j.1365-2966.2003.07114.x
published as Mon.Not.Roy.Astron.Soc. 346 (2003) 601 · 15 pages, 20 figures, 2003, MNRAS, 346, 601
arxiv created 2003/12/01 · arxiv updated 2009/12/01
We have studied the morphology-density relation and morphology--cluster-centric-radius relation using a volume limited sample (0.05<z<0.1, Mr^*<-20.5) of the Sloan Digital Sky Survey (SDSS) data. We found there are two characteristic changes in both the morphology-density and the morphology-radius relations, suggesting two different mechanisms are responsible for the relations. In the sparsest regions (below 1 Mpc-2 or outside of 1 virial radius), both relations become less noticeable, suggesting the responsible physical mechanisms for galaxy morphological change require denser environment. In the intermediate density regions (density between 1 and 6 Mpc-2 or virial radius between 0.3 and 1), intermediate-type fractions increase toward denser regions, whereas late-disc fractions decrease. In the densest regions (above 6 Mpc-2 or inside of 0.3 virial radius), intermediate-type fractions decrease radically and early-type fractions increase in turn. This is a contrasting result to that in intermediate regions and it suggests that yet another mechanism is more responsible for the morphological change in these regions. We also compared the morphology-density relation from the SDSS (0.01<z<0.054) with that of the MORPHS data (z∼0.5). Two relations lie on top of each other, suggesting that the morphology-density relation was already established at z∼0.5 as is in the present universe.