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Starburst Galaxies in Cluster-feeding Filaments Unveiled by <i>Spitzer</i>

D. FaddaKitt Peak National ObservatoryA. BivianoINAF-Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, I-34143 Trieste, ItalyF. MarleauSpitzer Science Center, California Institute of Technology, Mail Code 220-6, Pasadena, CA 91125Lisa J. Storrie‐LombardiSpitzer Science Center, California Institute of Technology, Mail Code 220-6, Pasadena, CA 91125Florence DurretInstitut d’Astrophysique de Paris, CNRS, Université Pierre et Marie Curie, 98bis Boulevard Arago, F-75014 Paris, France

2007en

ABI

Annotatsiya

We report the first direct detection with Spitzer of galaxy filaments. Using Spitzer and ancillary optical data, we have discovered two filamentary structures in the outskirts of the cluster Abell 1763. Both filaments point toward Abell 1770, which lies at the same redshift as Abell 1763 (z = 0.23), at a projected distance of ~13 Mpc. The X-ray cluster emission is elongated along the same direction. Most of the far-infrared emission is powered by star formation. According to the optical spectra, only one of the cluster members is classified as an active galactic nucleus. Star formation is clearly enhanced in galaxies along the filaments: the fraction of starburst galaxies in the filaments is more than twice than that in other cluster regions. We speculate that these filaments are feeding the cluster Abell 1763 by the infall of galaxies and galaxy groups. Evidence for one of these groups is provided by the analysis of galaxy kinematics in the central cluster region.

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DOI: 10.1086/526457

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