Abstract
We present an investigation of the properties and environments of bright extremely red objects (EROs) found in the fields of the quasars TXS 0145+386 and 4C 15.55, both at z � 1:4. There is marginal evidence from Chandra Advanced CCD Imaging Spectrometer (ACIS) imaging for hot cluster gas with a luminosity of a few 10 44 ergs s � 1 in the field of 4C 15.55. The TXS 0145+386 field has an upper limit at a similar value, but it also clearly shows an overdensityof faintgalaxies. Noneof theEROsaredetectedasX-raysources.FortwooftheEROsthathavespectral energy distributions and rest-frame near-UV spectra that show that they are strongly dominated by old stellar populations, we determine radial surface brightness profiles from adaptive optics images. Both of these galaxies are best fit by profiles close to exponentials, plus a compact nucleus comprising � 30% of the total light in one case and 8% in the other. Neither is well fit by an r 1/4 -law profile. This apparent evidence for the formation of massive � 2 ;10 11 disks of old stars in the early universe indicates that at least some galaxies formed essentially monolithically, with high star formation rates sustained over a few 10 8 yr and without the aid of major mergers. Subject headingg galaxies: evolution — galaxies: formation — galaxies: high-redshift
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