Hamilton’s Object - a clumpy galaxy straddling the gravitational caustic of a galaxy cluster

• Verfasst von: Griffiths, Richard [VerfasserIn]
• Verfasst von: Rudisel, Mitchell [VerfasserIn]
• Verfasst von: Wagner, Jennifer [VerfasserIn]
• Verfasst von: Hamilton, Timothy [VerfasserIn]
• Verfasst von: Huang, Po-Chieh [VerfasserIn]
• Verfasst von: Villforth, Carolin [VerfasserIn]
• Titel: Hamilton’s Object - a clumpy galaxy straddling the gravitational caustic of a galaxy cluster
• Titelzusatz: constraints on dark matter clumping
• Verf.angabe: Richard E. Griffiths, Mitchell Rudisel, Jenny Wagner, Timothy Hamilton, Po-Chieh Huang and Carolin Villforth
• E-Jahr: 2021
• Jahr: 17 May 2021
• Umfang: 14 S.
• Fussnoten: Gesehen am 24.11.2021
• Titel Quelle: Enthalten in: Royal Astronomical SocietyMonthly notices of the Royal Astronomical Society
• Ort Quelle: Oxford : Oxford Univ. Press, 1827
• Jahr Quelle: 2021
• Band/Heft Quelle: 506(2021), 2, Seite 1595-1608
• ISSN Quelle: 1365-2966
• DOI: doi:10.1093/mnras/stab1375
• Datenträger: Online-Ressource
• Sprache: eng
• K10plus-PPN: 1778918131

Abstract

We report the discovery of a ‘folded’ gravitationally lensed image, ‘Hamilton’s Object’, found in a HST image of the field near the active galactic nucleus SDSS J223010.47-081017.8 (which has redshift 0.62). The lensed images are sourced by a galaxy at a spectroscopic redshift of 0.8200 ± 0.0005 and form a fold configuration on a caustic caused by a foreground galaxy cluster at a photometric redshift of 0.526 ± 0.018 seen in the corresponding Pan-STARRS PS1 image and marginally detected as a faint ROSAT All-Sky Survey X-ray source. The lensed images exhibit properties similar to those of other ‘folds’ where the source galaxy falls very close to or straddles the caustic of a galaxy cluster. The folded images are stretched in a direction roughly orthogonal to the critical curve, but the configuration is that of a tangential cusp. Guided by morphological features, published simulations and similar ‘fold’ observations in the literature, we identify a third or ‘counter’-image, confirmed by spectroscopy. Because the fold-configuration shows highly distinctive surface brightness features, follow-up observations of microlensing or detailed investigations of the individual surface brightness features at higher resolution can further shed light on kpc-scale dark matter properties. We determine the local lens properties at the positions of the multiple images according to the observation-based lens reconstruction of Wagner. The analysis is in accordance with a mass density which hardly varies on an arcsecond scale (6 kpc) over the areas covered by the multiple images.