期刊
ASTRONOMY & ASTROPHYSICS
卷 507, 期 2, 页码 671-U130出版社
EDP SCIENCES S A
DOI: 10.1051/0004-6361/200912675
关键词
galaxies: evolution; galaxies: clusters: individual: RDCS J1252-29; cosmology: large-scale structure of Universe
资金
- Association of Universities for Research in Astronomy Inc.
- National Science Foundation (United States)
- Science and Technology Facilities Council (United Kingdom)
- National Research Council (Canada)
- CONICYT (Chile)
- Australian Research Council (Australia)
- Ministerio da Ciencia e Tecnologia (Brazil)
- SECYT (Argentina)
- National Astronomical Observatory of Japan
- United Kingdom Infrared Telescope
- Joint Astronomy Centre
- Astronomy Research Council
- NAOJ
- SDSS
- Alfred P. Sloan Foundation
- Participating Institutions
- National Science Foundatio
- U. S. Department of Energy
- National Aeronautics and Space Administration
- Japanese Monbukagakusho
- Max Planck Society
- Higher Education Funding Council for England
- Japanese Ministry of Education, Culture, Sports and Science [18684004, 21340045]
- NASA [NNX08AD93G]
- Grants-in-Aid for Scientific Research [18684004] Funding Source: KAKEN
- NASA [103023, NNX08AD93G] Funding Source: Federal RePORTER
- Science and Technology Facilities Council [ST/F002963/1, ST/H008519/1, ST/F002289/1] Funding Source: researchfish
- STFC [ST/F002963/1, ST/F002289/1, ST/H008519/1] Funding Source: UKRI
Recent wide-field imaging observations of the X-ray luminous cluster RDCS J1252.9-2927 at z = 1.24 uncovered several galaxy groups that appear to be embedded in filamentary structure extending from the cluster core. We make a spectroscopic study of the galaxies in these groups using GMOS on Gemini-South and FORS2 on VLT with the aim of determining if these galaxies are physically associated to the cluster. We find that three groups contain galaxies at the cluster redshift and that they are probably bound to the cluster. This is the first confirmation of filamentary structure as traced by galaxy groups at z > 1. We then use several spectral features in the FORS2 spectra to determine the star formation histories of group galaxies. We find a population of relatively red star-forming galaxies in the groups that are absent from the cluster core. While similarly red star forming galaxies can also be found in the field, the average strength of the H delta line is systematically weaker in group galaxies. Interestingly, these groups at z = 1.2 are in an environment in which the on-going build-up of red sequence is happening. The unusual line strengths can be explained by star formation that is heavily obscured by dust. We hypothesize that galaxy-galaxy interactions, which is more efficient in the group environment, is the mechanism that drives these dust obscured star formation. The hypothesis can be tested by obtaining spectral observations in the near-IR, high resolution imaging observations and observations in the mid-IR.
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