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Title: H0LiCOW – II. Spectroscopic survey and galaxy-group identification of the strong gravitational lens system HE 0435-1223

Galaxies located in the environment or on the line of sight towards gravitational lenses can significantly affect lensing observables, and can lead to systematic errors on the measurement of H 0 from the time-delay technique. We present the results of a systematic spectroscopic identi cation of the galaxies in the field of view of the lensed quasar HE0435-1223 using the W. M. Keck, Gemini and ESO-Very Large telescopes. Our new catalog triples the number of known galaxy redshifts in the direct vicinity of the lens, expanding to 102 the number of measured redshifts for galaxies separated by less than 30 from the lens. We complement our catalog with literature data to gather redshifts up to 150 from the lens, and search for galaxy groups or clusters projected towards HE0435-1223. We con rm that the lens is a member of a small group that includes at least 12 galaxies, and nd 8 other group candidates near the line of sight of the lens. The flexion shift, namely the shift of lensed images produced by high order perturbation of the lens potential, is calculated for each galaxy/group and used to identify which objects produce the largest perturbation of the lens potential. Thismore » analysis demonstrates that i) at most three of the five brightest galaxies projected within 1200 of the lens need to be explicitly used in the lens models, and ii) the groups can be treated in the lens model as an external tidal field (shear) contribution.« less
 [1] ;  [2] ;  [3] ;  [3] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ;  [9] ;  [8] ;  [10] ;  [11] ;  [12] ;  [8] ;  [13] ;  [14]
  1. Univ. of Liege, (Belgium). STAR Inst.
  2. Univ. of California, Santa Barbara, CA (United States); Univ. of California, Los Angeles, CA (United States); Univ. of Tokyo (Japan)
  3. Univ. of California, Davis, CA (United States)
  4. Univ. of California, Los Angeles, CA (United States)
  5. Academia Sinica, Taipei (Taiwan); Max Planck Society, Garching (Germany). Max Planck Inst. for Astrophysics; Technische Univ. Munchen, Garching (Germany)
  6. Academia Sinica, Taipei (Taiwan); National Astronomical Observatory of Japan, Tokyo (China)
  7. Univ. of Cambridge (United Kingdom)
  8. Ecole Polytechnique Federale Lausanne (Switzlerland). Observatoire de Sauverny
  9. Univ. of Portsmouth (United Kingdom)
  10. Ludwig Maximilian Univ., Munich (Germany); Exzellenzcluster Universe, Garching (Germany)
  11. Univ. of Groningen (The Netherlands). Kapteyn Astronomical Inst.
  12. Stanford Univ., CA (United States). Kavli Inst. for Particle Astrophysics and Cosmology
  13. Max Planck Society, Garching (Germany). Max Planck Inst. for Astrophysics
  14. Argelander Inst. for Astronomy, Bonn (Germany)
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Monthly Notices of the Royal Astronomical Society
Additional Journal Information:
Journal Volume: 470; Journal Issue: 4; Journal ID: ISSN 0035-8711
Royal Astronomical Society
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
Country of Publication:
United States
79 ASTRONOMY AND ASTROPHYSICS; gravitational lensing: strong; galaxies: groups: general; quasars: individual: HE 0435−1223
OSTI Identifier: