THE ATACAMA COSMOLOGY TELESCOPE: ACT-CL J0102-4915 'EL GORDO', A MASSIVE MERGING CLUSTER AT REDSHIFT 0.87
- Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Rd, Piscataway, NJ 08854 (United States)
- Departamento de Astronomia y Astrofisica, Facultad de Fisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile)
- School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom)
- Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, ON M5S 3H8 (Canada)
- Berkeley Center for Cosmological Physics, LBL and Department of Physics, University of California, Berkeley, CA 94720 (United States)
- Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States)
- Department of Astrophysics, Oxford University, Oxford, OX1 3RH (United Kingdom)
- Joseph Henry Laboratories of Physics, Jadwin Hall, Princeton University, Princeton, NJ 08544 (United States)
- Physics and Astronomy Department, University of Pittsburgh, 100 Allen Hall, 3941 O'Hara Street, Pittsburgh, PA 15260 (United States)
- Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD 21218-2686 (United States)
- Astrophysics and Cosmology Research Unit, School of Mathematical Sciences, University of KwaZulu-Natal, Durban 4041 (South Africa)
- NIST Quantum Devices Group, 325 Broadway Mailcode 817.03, Boulder, CO 80305 (United States)
We present a detailed analysis from new multi-wavelength observations of the exceptional galaxy cluster ACT-CL J0102-4915, likely the most massive, hottest, most X-ray luminous and brightest Sunyaev-Zel'dovich (SZ) effect cluster known at redshifts greater than 0.6. The Atacama Cosmology Telescope (ACT) collaboration discovered ACT-CL J0102-4915 as the most significant SZ decrement in a sky survey area of 755 deg{sup 2}. Our Very Large Telescope (VLT)/FORS2 spectra of 89 member galaxies yield a cluster redshift, z = 0.870, and velocity dispersion, {sigma}{sub gal} = 1321 {+-} 106 km s{sup -1}. Our Chandra observations reveal a hot and X-ray luminous system with an integrated temperature of T{sub X} = 14.5 {+-} 0.1 keV and 0.5-2.0 keV band luminosity of L{sub X} = (2.19 {+-} 0.11) Multiplication-Sign 10{sup 45} h{sup -2}{sub 70} erg s{sup -1}. We obtain several statistically consistent cluster mass estimates; using empirical mass scaling relations with velocity dispersion, X-ray Y{sub X}, and integrated SZ distortion, we estimate a cluster mass of M{sub 200a} = (2.16 {+-} 0.32) Multiplication-Sign 10{sup 15} h{sup -1}{sub 70} M{sub Sun }. We constrain the stellar content of the cluster to be less than 1% of the total mass, using Spitzer IRAC and optical imaging. The Chandra and VLT/FORS2 optical data also reveal that ACT-CL J0102-4915 is undergoing a major merger between components with a mass ratio of approximately 2 to 1. The X-ray data show significant temperature variations from a low of 6.6 {+-} 0.7 keV at the merging low-entropy, high-metallicity, cool core to a high of 22 {+-} 6 keV. We also see a wake in the X-ray surface brightness and deprojected gas density caused by the passage of one cluster through the other. Archival radio data at 843 MHz reveal diffuse radio emission that, if associated with the cluster, indicates the presence of an intense double radio relic, hosted by the highest redshift cluster yet. ACT-CL J0102-4915 is possibly a high-redshift analog of the famous Bullet cluster. Such a massive cluster at this redshift is rare, although consistent with the standard {Lambda}CDM cosmology in the lower part of its allowed mass range. Massive, high-redshift mergers like ACT-CL J0102-4915 are unlikely to be reproduced in the current generation of numerical N-body cosmological simulations.
- OSTI ID:
- 22016202
- Journal Information:
- Astrophysical Journal, Vol. 748, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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