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A unique small-scale gravitational arc in A1201

Edge, A.C; Smith, G.P; Sand, D.J; Treu, T.; Ebeling, H.; Allen, S.W.; van Dokkum, P.G.


G.P Smith

D.J Sand

T. Treu

H. Ebeling

S.W. Allen

P.G. van Dokkum


We present a snapshot Hubble Space Telescope (HST) image of the galaxy cluster A1201 (z=0.169), revealing a tangential arc 2 from the brightest cluster galaxy (BCG). Keck Echelle Spectrograph and Imager (ESI) spectroscopy confirms that the arc is gravitational in nature and that the source galaxy lies at z=0.451. We construct a model of the gravitational potential of the cluster that faithfully reproduces the observed arc morphology. Despite the relaxed appearance of the cluster in the HST frame, the best-fit ellipticity of the total matter distribution is total0.5, in contrast to the light distribution of the BCG (BCG=0.23±0.03) on 2 scales. Further deep optical observations and pointed X-ray spectro-imaging observations with Chandra are required to determine whether this elongation is due to a single elongated dark matter halo or a more complex distribution of matter in the cluster core. We compare the arc with a sample drawn from the published literature and confirm that it is unique among tangential systems in the small physical scales that it probes (6 kpc). In anticipation of a more thorough investigation of this cluster across a broad range of physical scales, we use our fiducial lens model to estimate the projected mass and mass-to-light ratio of the cluster within a radius of 6 kpc, obtaining M=(5.9+0.9-0.7)×1011 M, M/LV=9.4+2.4-2.1 (M/L). Overall our results confirm the importance of HST snapshot surveys for identifying rare lensing constraints on cluster mass distributions. In combination with follow-up optical and X-ray observations, the arc in A1201 should help to increase our understanding of the physics of cluster cores.


Edge, A., Smith, G., Sand, D., Treu, T., Ebeling, H., Allen, S., & van Dokkum, P. (2003). A unique small-scale gravitational arc in A1201. Astrophysical Journal Letters, 599(2), L69-L72.

Journal Article Type Article
Publication Date Dec 20, 2003
Deposit Date May 20, 2008
Journal Astrophysical Journal Letters
Print ISSN 2041-8205
Electronic ISSN 2041-8213
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 599
Issue 2
Pages L69-L72
Keywords Galaxies, Clusters, Gravitational lensing, Hubble-space-telescope, Luminous galaxy clusters, Cold dark-matter, X-ray, Chandra observations, Lensing survey, Mass, Spectrograph, Profile.