2003/12/06 by Joshua N. Winn, D. Rusin, David Rusin +2 · 109 citations
Physics and Astronomy · #Artificial intelligence #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Computer science #Galaxies: Formation, Evolution, Phenomena #Galaxy #Gravitational lens #Image (mathematics) #Lens (geology) #Optics #Physics #Quasar #Radio Astronomy Observations and Technology #Redshift #Solar mass #astro-ph
paper · pdf · doi:10.1038/nature02279
published in Nature 427(6975), 613-615 (Nature Portfolio) · Nature, in press [7 pp, 2 figs]. Standard media embargo applies before publication
arxiv created 2003/12/06 · openalex publication_date 2004/02/01 · arxiv updated 2015/06/24 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
A galaxy can act as a gravitational lens, producing multiple images of a background object. Theory predicts there should be an odd number of images but, paradoxically, almost all observed lenses have 2 or 4 images. The missing image should be faint and appear near the galaxy's center. These ``central images'' have long been sought as probes of galactic cores too distant to resolve with ordinary observations. There are five candidates, but in one case the third image is not necessarily a central image, and in the others, the central component might be a foreground source rather than a lensed image. Here we report the most secure identification of a central image, based on radio observations of PMN J1632-0033, one of the latter candidates. Lens models incorporating the central image show that the mass of the lens galaxy's central black hole is less than 2 x 108 Msun, and the galaxy's surface density at the location of the central image is more than 20,000 Msun per square parsec, in agreement with expectations based on observations of galaxies hundreds of times closer to the Earth.