A strongly lensed massive ultracompact quiescent galaxy at z ∼ 2.4 in the COSMOS/UltraVISTA field

Adam Muzzin, Ivo Labbé, Marijn Franx, Pieter Van Dokkum, J. Holt, Daniel Szomoru, Jesse Van De Sande, Gabriel Brammer, Danilo Marchesini, Mauro Stefanon, F. Buitrago, K. I. Caputi, James Dunlop, J. P.U. Fynbo, Olivier Le Févre, Henry J. McCracken, Bo Milvang-Jensen

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16 Citations (Scopus)


We report the discovery of a massive ultracompact quiescent galaxy that has been strongly lensed into multiple images by a foreground galaxy at z = 0.960. This system was serendipitously discovered as a set of extremely K s-bright high-redshift galaxies with red J - Kscolors using new data from the UltraVISTA YJHKsnear-infrared survey. The system was also previously identified as an optically faint lens/source system using the COSMOS Advanced Camera for Surveys (ACS) imaging by Faure et al. Photometric redshifts for the three brightest images of the source galaxy determined from 27-band photometry place the source at z = 2.4 ± 0.1. We provide an updated lens model for the system that is a good fit to the positions and morphologies of the galaxies in the ACS image. The lens model implies that the magnification of the three brightest images is a factor of 4-5. We use the lens model, combined with the Ks-band image, to constrain the size and Sérsic profile of the galaxy. The best-fit model is an ultracompact galaxy (Re= 0.64+0.08-0.18 kpc, lensing-corrected), with a Sérsic profile that is intermediate between a disk and a bulge profile (n = 2.2+2.3-0.9), albeit with considerable uncertainties on the Sérsic profile. We present aperture photometry for the source galaxy images that have been corrected for flux contamination from the central lens. The best-fit stellar population model is a massive galaxy (log(M ⊙star/M⊙) = 10.8+0.1 - 0.1, lensing-corrected) with an age of 1.0+1.0- 0.4 Gyr, moderate dust extinction (Av= 0.8+0.5- 0.6), and a low specific star formation rate (log(SSFR)
Original languageEnglish
JournalAstrophysical Journal
Issue number2
Publication statusPublished - 10 Dec 2012


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