---
res:
  bibo_abstract:
  - Gravitational lensing can amplify the apparent brightness of distant sources.
    Images that are highly magnified are often part of multiply imaged systems, but
    we consider the possibility of having large magnifications without additional
    detectable images. In rare but nonnegligible situations, lensing can produce a
    single highly magnified image; this phenomenon is mainly associated with massive
    cluster-scale halos (≳1013.5 M☉). Alternatively, lensing can produce multiply
    imaged systems in which the extra images are either unresolved or too faint to
    be detectable. This phenomenon is dominated by galaxies and lower mass halos (≲1012
    M☉) and is very sensitive to the inner density profile of the halos. Although
    we study the general problem, we customize our calculations to four quasars at
    redshift z ≈ 6 in the Sloan Digital Sky Survey (SDSS), for which Richards et al.
    (2004) have ruled out the presence of extra images down to an image splitting
    of Δθ = 0farcs3 and a flux ratio of f = 0.01. We predict that 9%-29% of all z
    ≈ 6 quasars that are magnified by a factor of μ > 10 would lack detectable extra
    images, with 5%-10% being true singly imaged systems. The maximum of 29% is reached
    only in the unlikely event that all low-mass (≲1010 M☉) halos have highly concentrated
    (isothermal) profiles. In more realistic models in which dwarf halos have flatter
    (Navarro-Frenk-White) inner profiles, the maximum probability is ~10%. We conclude
    that the probability that all four SDSS quasars are magnified by a factor of 10
    is ≲10-4. The only escape from this conclusion is if there are many (>10) multiply
    imaged z ≈ 6 quasars in the SDSS database that have not yet been identified, which
    seems unlikely. In other words, lensing cannot explain the brightnesses of the
    z ≈ 6 quasars, and models that invoke lensing to avoid having billion-solar-mass
    black holes in the young universe are not viable.@eng
  bibo_authorlist:
  - foaf_Person:
      foaf_givenName: Charles R.
      foaf_name: Keeton, Charles R.
      foaf_surname: Keeton
  - foaf_Person:
      foaf_givenName: Michael
      foaf_name: Kuhlen, Michael
      foaf_surname: Kuhlen
  - foaf_Person:
      foaf_givenName: Zoltán
      foaf_name: Haiman, Zoltán
      foaf_surname: Haiman
      foaf_workInfoHomepage: http://www.librecat.org/personId=7c006e8c-cc0d-11ee-8322-cb904ef76f36
    orcid: 0000-0003-3633-5403
  bibo_doi: 10.1086/427722
  bibo_issue: '2'
  bibo_volume: 621
  dct_date: 2005^xs_gYear
  dct_isPartOf:
  - http://id.crossref.org/issn/0004-637X
  - http://id.crossref.org/issn/1538-4357
  dct_language: eng
  dct_publisher: American Astronomical Society@
  dct_title: Gravitational lensing magnification without multiple imaging@
...