We perform a morphological study of 124 spectroscopically confirmed cluster galaxies in the redshift (z) = 0.84 galaxy cluster RX J0152.7-1357. Our classification scheme includes color information, visual morphology, and one-and two-component light profile fitting derived from Hubble Space Telescope riz imaging. We adopt a modified version of a detailed classification scheme previously used in studies of field galaxies and found to be correlated with kinematic features of those galaxies. We compare our cluster galaxy morphologies to those of field galaxies at similar redshift. We also compare galaxy morphologies in regions of the cluster with different dark-matter density as determined by weak-lensing maps. We find an early-type fraction for the cluster population as a whole of 47%, about 2.8 times higher than the field, and similar to the dynamically young cluster MS 1054 at similar redshift. We find the most drastic change in morphology distribution between the low and intermediate dark-matter density regions within the cluster, with the early-type fraction doubling and the peculiar fraction dropping by nearly half. The peculiar fraction drops more drastically than the spiral fraction going from the outskirts to the intermediate-density regions. This suggests that many galaxies falling into clusters at z ∼ 0.8 may evolve directly from peculiar, merging, and compact systems into early-type galaxies, without having the chance to first evolve into a regular spiral galaxy.
Bibliographical noteFunding Information:
J.N. acknowledges the support provided by FONDECYT postdoctoral research grant N. 3120233. R.D. gratefully acknowledges the support provided by the BASAL Center for Astrophysics and Associated Technologies (CATA), and by FONDECYT grants N. 1100540 and N. 1130528. C.L. is the recipient of an Australian Research Council Future Fellowship (program number FT0992259). This research is based on observations with the Hubble Space Telescope obtained at the Space Telescope Science Institute, operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with Program GO-9290. Spectroscopic data for cluster member confirmation were obtained from FORS1 and FORS2 observations at the ESO VLT as part of programs 166.A-0701, 69.A-0683, 72.A-0759, and 076.A-0889. We would like to thank M. Postman for providing the full set of visual T-type classifications and a clarification of the definition of early types via private communication.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science