The morphology-density relation in the Sloan Digital Sky Survey

被引:421
作者
Goto, T
Yamauchi, C
Fujita, Y
Okamura, S
Sekiguchi, M
Smail, I
Bernardi, M
Gomez, PL
机构
[1] Univ Tokyo, Inst Cosm Ray Res, Chiba 2770882, Japan
[2] Univ Tokyo, Grad Sch Sci, Dept Astron, Bunkyo Ku, Tokyo 1130033, Japan
[3] Natl Astron Observ, Tokyo 1818588, Japan
[4] Univ Durham, Dept Phys, Durham DH1 3LE, England
[5] Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA
关键词
galaxies; clusters; general;
D O I
10.1046/j.1365-2966.2003.07114.x
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
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. Major improvements compared with previous work are: (i) automated galaxy morphology classification capable of separating galaxies into four types; (ii) three-dimensional local galaxy density estimation; and (iii) the extension of the morphology-density relation into the field region. We found that the morphology-density and morphology-cluster-centric- radius relation in the SDSS data for both of our automated morphological classifiers, Cin and Tauto, as fractions of early-type galaxies increase and late-type galaxies decrease toward increasing local galaxy density. In addition, we found that there are two characteristic changes in both the morphology-density and the morphology-radius relations, suggesting that 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 that the physical mechanisms responsible for galaxy morphological change require a 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. Considering that the median size of intermediate-type galaxies is smaller than that of late-disc galaxies, we propose that the mechanism is likely to stop star formation in late-disc galaxies, eventually turning them into intermediate- type galaxies after their outer discs and spiral arms become invisible as stars die. For example, ram-pressure stripping is one of the candidate mechanisms. In the densest regions (above 6 Mpc(-2) or inside 0.3 virial radii), 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 similar to 0.5). Two relations lie on top of each other, suggesting that the morphology-density relation was already established at z similar to 0.5 as in the present Universe. A slight sign of an excess elliptical/S0 fraction in the SDSS data in dense regions might suggest the additional formation of elliptical/S0 galaxies in the cluster core regions between z = 0 5 and 0.05.
引用
收藏
页码:601 / 614
页数:14
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