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Title: VLT AND ACS OBSERVATIONS OF RDCS J1252.9-2927: DYNAMICAL STRUCTURE AND GALAXY POPULATIONS IN A MASSIVE CLUSTER AT Z=1.237*

Abstract

We present results from an extensive spectroscopic survey, carried out with FORS on the ESO Very Large Telescope, and from an extensive multi-wavelength imaging data set from the Advanced Camera for Surveys and ground based facilities of the cluster of galaxies RDCS J1252.9-2927. We have spectroscopically confirmed 38 cluster members in the redshift range 1.22 < z < 1.25. The distribution in velocity of these spectroscopic members yields a cluster median redshift of z = 1.237 and a rest-frame velocity dispersion of 747{sub -84}{sup +74} km s{sup -1}. Star-forming members are observed to mainly populate the outskirts of the cluster while passive galaxies dominate the central cluster region. Using the 38 confirmed redshifts, we were able to resolve, for the first time at z > 1, kinematic structure. The velocity distribution, which is not Gaussian at the 95% confidence level, is consistent with two groups that are also responsible for the projected elongation of the cluster in the East-West direction. The groups are composed of 26 and 12 galaxies and have velocity dispersions of 486{sub -85}{sup +47} km s{sup -1} and 426{sub -105}{sup +57} km s{sup -1}, respectively. The elongation is also seen in the intracluster gas (from X-ray observations)more » and the dark matter distribution (from a weak lensing analysis). This leads us to conclude that RDCS J1252.9-2927 has not yet reached a final virial state. We extend the analysis of the color-magnitude diagram of spectroscopic members to more than 1 Mpc from the cluster center. The scatter and slope of non-[OII]-emitting cluster members in the near-IR red sequence is similar to that seen in clusters at lower redshift. Furthermore, none of the galaxies with luminosities greater than {approx} K*{sub s} + 1.5 show any [OII] emission feature, indicating that these more luminous, redder galaxies have stopped forming stars earlier than the fainter, bluer galaxies. Our observations provide detailed dynamical and spectrophotometric information of galaxies in this exceptional high-redshift cluster, delivering an in-depth view of structure formation at this epoch only 5 Gyr after the Big Bang. In addition, we present the spectra of a few X-ray point sources in the cluster field of view.« less

Authors:
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Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
940877
Report Number(s):
UCRL-JRNL-229399
Journal ID: ISSN 0004-637X; ASJOAB; TRN: US200824%%373
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Journal Article
Resource Relation:
Journal Name: The Astrophysical Journal, vol. 663, no. 1, July 1, 2007, pp. 164-182; Journal Volume: 663; Journal Issue: 1
Country of Publication:
United States
Language:
English
Subject:
99 GENERAL AND MISCELLANEOUS; CAMERAS; DISTRIBUTION; ELONGATION; GALAXIES; NONLUMINOUS MATTER; POINT SOURCES; SPECTRA; STARS; VELOCITY

Citation Formats

Demarco, R, Rosati, P, Lidman, C, Girardi, M, Nonino, M, Rettura, A, Strazzullo, V, der Wel, A v, Ford, H C, Mainieri, V, Holden, B P, Stanford, S A, Blakeslee, J P, Gobat, R, Postman, M, Tozzi, P, Overzier, R A, Zirm, A W, Benitez, N, Homeier, N L, Illingworth, G D, Infante, L, Jee, M J, Mei, S, Menanteau, F, Motta, V, Zheng, W, Clampin, M, and Hartig, G. VLT AND ACS OBSERVATIONS OF RDCS J1252.9-2927: DYNAMICAL STRUCTURE AND GALAXY POPULATIONS IN A MASSIVE CLUSTER AT Z=1.237*. United States: N. p., 2007. Web. doi:10.1086/518117.
Demarco, R, Rosati, P, Lidman, C, Girardi, M, Nonino, M, Rettura, A, Strazzullo, V, der Wel, A v, Ford, H C, Mainieri, V, Holden, B P, Stanford, S A, Blakeslee, J P, Gobat, R, Postman, M, Tozzi, P, Overzier, R A, Zirm, A W, Benitez, N, Homeier, N L, Illingworth, G D, Infante, L, Jee, M J, Mei, S, Menanteau, F, Motta, V, Zheng, W, Clampin, M, & Hartig, G. VLT AND ACS OBSERVATIONS OF RDCS J1252.9-2927: DYNAMICAL STRUCTURE AND GALAXY POPULATIONS IN A MASSIVE CLUSTER AT Z=1.237*. United States. doi:10.1086/518117.
Demarco, R, Rosati, P, Lidman, C, Girardi, M, Nonino, M, Rettura, A, Strazzullo, V, der Wel, A v, Ford, H C, Mainieri, V, Holden, B P, Stanford, S A, Blakeslee, J P, Gobat, R, Postman, M, Tozzi, P, Overzier, R A, Zirm, A W, Benitez, N, Homeier, N L, Illingworth, G D, Infante, L, Jee, M J, Mei, S, Menanteau, F, Motta, V, Zheng, W, Clampin, M, and Hartig, G. Fri . "VLT AND ACS OBSERVATIONS OF RDCS J1252.9-2927: DYNAMICAL STRUCTURE AND GALAXY POPULATIONS IN A MASSIVE CLUSTER AT Z=1.237*". United States. doi:10.1086/518117. https://www.osti.gov/servlets/purl/940877.
@article{osti_940877,
title = {VLT AND ACS OBSERVATIONS OF RDCS J1252.9-2927: DYNAMICAL STRUCTURE AND GALAXY POPULATIONS IN A MASSIVE CLUSTER AT Z=1.237*},
author = {Demarco, R and Rosati, P and Lidman, C and Girardi, M and Nonino, M and Rettura, A and Strazzullo, V and der Wel, A v and Ford, H C and Mainieri, V and Holden, B P and Stanford, S A and Blakeslee, J P and Gobat, R and Postman, M and Tozzi, P and Overzier, R A and Zirm, A W and Benitez, N and Homeier, N L and Illingworth, G D and Infante, L and Jee, M J and Mei, S and Menanteau, F and Motta, V and Zheng, W and Clampin, M and Hartig, G},
abstractNote = {We present results from an extensive spectroscopic survey, carried out with FORS on the ESO Very Large Telescope, and from an extensive multi-wavelength imaging data set from the Advanced Camera for Surveys and ground based facilities of the cluster of galaxies RDCS J1252.9-2927. We have spectroscopically confirmed 38 cluster members in the redshift range 1.22 < z < 1.25. The distribution in velocity of these spectroscopic members yields a cluster median redshift of z = 1.237 and a rest-frame velocity dispersion of 747{sub -84}{sup +74} km s{sup -1}. Star-forming members are observed to mainly populate the outskirts of the cluster while passive galaxies dominate the central cluster region. Using the 38 confirmed redshifts, we were able to resolve, for the first time at z > 1, kinematic structure. The velocity distribution, which is not Gaussian at the 95% confidence level, is consistent with two groups that are also responsible for the projected elongation of the cluster in the East-West direction. The groups are composed of 26 and 12 galaxies and have velocity dispersions of 486{sub -85}{sup +47} km s{sup -1} and 426{sub -105}{sup +57} km s{sup -1}, respectively. The elongation is also seen in the intracluster gas (from X-ray observations) and the dark matter distribution (from a weak lensing analysis). This leads us to conclude that RDCS J1252.9-2927 has not yet reached a final virial state. We extend the analysis of the color-magnitude diagram of spectroscopic members to more than 1 Mpc from the cluster center. The scatter and slope of non-[OII]-emitting cluster members in the near-IR red sequence is similar to that seen in clusters at lower redshift. Furthermore, none of the galaxies with luminosities greater than {approx} K*{sub s} + 1.5 show any [OII] emission feature, indicating that these more luminous, redder galaxies have stopped forming stars earlier than the fainter, bluer galaxies. Our observations provide detailed dynamical and spectrophotometric information of galaxies in this exceptional high-redshift cluster, delivering an in-depth view of structure formation at this epoch only 5 Gyr after the Big Bang. In addition, we present the spectra of a few X-ray point sources in the cluster field of view.},
doi = {10.1086/518117},
journal = {The Astrophysical Journal, vol. 663, no. 1, July 1, 2007, pp. 164-182},
number = 1,
volume = 663,
place = {United States},
year = {Fri Mar 23 00:00:00 EDT 2007},
month = {Fri Mar 23 00:00:00 EDT 2007}
}