Browsing by Author "Heymans, C."

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Discovery of Two Einstein Crosses from Massive Post-blue Nugget Galaxies at z > 1 in KiDS*
    (2020) Napolitano, N. R.; Li, R.; Spiniello, C.; Tortora, C.; Sergeyev, A.; D'Ago, G.; Guo, X.; Xie, L.; Radovich, M.; Roy, N.; Koopmans, L. V. E.; Kuijken, K.; Bilicki, M.; Erben, T.; Getman, F.; Heymans, C.; Hildebrandt, H.; Moya, C.; Shan, H. Y.; Vernardos, G.; Wright, A. H.
    We report the discovery of two Einstein Crosses (ECs) in the footprint of the Kilo-Degree Survey (KiDS): KIDS J232940-340922 and KIDS J122456+005048. Using integral field spectroscopy from the Multi Unit Spectroscopic Explorer at the Very Large Telescope, we confirm their gravitational-lens nature. In both cases, the four spectra of the source clearly show a prominence of absorption features, hence revealing an evolved stellar population with little star formation. The lensing model of the two systems, assuming a singular isothermal ellipsoid (SIE) with external shear, shows that: (1) the two crosses, located at redshift z = 0.38 and 0.24, have Einstein radius R-E = 5.2 kpc and 5.4 kpc, respectively; (2) their projected dark matter fractions inside the half effective radius are 0.60 and 0.56 (Chabrier initial mass function); (3) the sources are ultra-compact galaxies, R-e similar to 0.9 kpc (at redshift, z(s) = 1.59) and R-e similar to 0.5 kpc (z(s) = 1.10), respectively. These results are unaffected by the underlying mass density assumption. Due to size, blue color, and absorption-dominated spectra, corroborated by low specific star formation rates derived from optical-near-infrared spectral energy distribution fitting, we argue that the two lensed sources in these ECs are blue nuggets migrating toward their quenching phase.
  • Thumbnail Image
    Item
    Ultra-deep catalog of X-ray groups in the Extended Chandra Deep Field South
    (2015) Finoguenov, A.; Tanaka, M.; Cooper, M.; Allevato, V.; Cappelluti, N.; Choi, A.; Heymans, C.; Bauer, Franz Erik; Ziparo, F.; Ranalli, P.; Silverman, J.; Brandt, W.; Xue, Y.; Mulchaey, J.; Howes, L.; Schmid, C.