The unrelaxed dynamical structure of the galaxy cluster Abell 85

Journal Article · Thu Nov 10 04:00:00 EST 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/831/2/156· OSTI ID:22868490

Yu, Heng ^[1]; Diaferio, Antonaldo; Agulli, Irene ^[2]; Aguerri, J. Alfonso L. ^[3]; Tozzi, Paolo ^[4]

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1. Department of Astronomy, Beijing Normal University, Beijing, 100875 (China)
2. Dipartimento di Fisica, Università di Torino, Via P. Giuria 1, I-10125 Torino (Italy)
3. Instituto de Astrofisica de Canarias, C/Via Lactea s/n, E-38200 La Laguna, Tenerife (Spain)
4. INAF Osservatorio Astrofisico di Arcetri, Largo E. Fermi, I-50122 Firenze (Italy)

For the first time, we explore the dynamics of the central region of a galaxy cluster within r {sub 500} ∼ 600 h{sup −1} kpc from its center by combining optical and X-ray spectroscopy. We use (1) the caustic technique, which identifies the cluster substructures and their galaxy members with optical spectroscopic data, and (2) the X-ray redshift fitting procedure, which estimates the redshift distribution of the intracluster medium (ICM). We use the spatial and redshift distributions of the galaxies and of the X-ray-emitting gas to associate the optical substructures to the X-ray regions. When we apply this approach to Abell 85 (A85), a complex dynamic structure of A85 emerges from our analysis: a galaxy group, with redshift z = 0.0509 ± 0.0021 is passing through the cluster center along the line of sight dragging part of the ICM present in the cluster core; two additional groups, at redshift z = 0.0547 ± 0.0022 and z = 0.0570 ± 0.0020, are going through the cluster in opposite directions, almost perpendicularly to the line of sight, and have substantially perturbed the dynamics of the ICM. An additional group in the outskirts of A85, at redshift z = 0.0561 ± 0.0023, is associated with a secondary peak of X-ray emission, at redshift z=0.0583{sub −0.0047}{sup +0.0039}. Although our analysis and results on A85 need to be confirmed by high-resolution spectroscopy, they demonstrate how our new approach can be a powerful tool to constrain the formation history of galaxy clusters by unveiling their central and surrounding structures.

• OSTI ID: 22868490
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 831; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
DISTRIBUTION
EMISSION
GALAXY CLUSTERS
RED SHIFT
RESOLUTION
X-RAY GALAXIES
X-RAY SPECTROSCOPY