Velocity dispersions and stellar populations of the most compact and massive early-type galaxies at redshift ~1

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We present Gran-Telescopio-Canarias/OSIRIS optical spectra of four of the most compact and massive early-type galaxies (ETGs) in the Groth Strip Survey at redshift z ~ 1, with effective radii R e = 0.5-2.4 kpc and photometric stellar masses M = (1.2-4) × 1011 M ☉. We find that these galaxies have velocity dispersions σ = 156-236 km s–1. The spectra are well fitted by single stellar population models with approximately 1 Gyr of age and solar metallicity. We find that (1) the dynamical masses of these galaxies are systematically smaller by a factor of ~6 than the published stellar masses using BRIJK photometry, and (2) when estimating stellar masses as 0.7× M dyn, a combination of passive luminosity fading with mass/size growth due to minor mergers can plausibly evolve our objects to match the properties of the local population of ETGs.
© 2011 The American Astronomical Society. Artículo firmado por 12 autores. This work is partially funded by the Spanish MICINN under the Consolider-Ingenio 2010 Program grant CSD2006- 00070: First Science with the GTC. J.M.M. acknowledges funding from a Graduate Alumni Fellowship at the University of Florida. The Spanish MICINN provides support to M.B., M.P., and A.H. through grant AYA2009-11137 and to J.G. through grant AYA2009-10368. Our observations were made with the GTC Telescope at the Spanish Observatorio del Roque de los Muchachos, which is managed by the Instituto de Astrofísica de Canarias. We are grateful to the personnel who took the observations and to Ana Matković for her help with the use of the RED ucmE software. We also thank the anonymous referee for useful comments that improved the presentation of this Letter.
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