Extremely Red Objects in Two Quasar Fields atz∼ 1.4

We present an investigation of the properties and environments of brightextremely red objects (EROs) found in the fields of the quasars TXS 0145+386and 4C 15.55, both at z ~ 1.4. There is marginal evidence from Chandra ACISimaging for hot cluster gas with a luminosity of a few 10^44 ergs/s in thefield of 4C 15.55. The TXS 0145+386 field has an upper limit at a similarvalue, but it also clearly shows an overdensity of faint galaxies. None of theEROs are detected as X-ray sources. For two of the EROs that havespectral-energy distributions and rest-frame near-UV spectra that show thatthey are strongly dominated by old stellar populations, we determineradial-surface-brightness profiles from adaptive-optics images. Both of thesegalaxies are best fit by profiles close to exponentials, plus a compact nucleuscomprising ~30% of the total light in one case and 8% in the other. Neither iswell fit by an r^1/4-law profile. This apparent evidence for the formation ofmassive ~2 X 10^11 disks of old stars in the early universe indicates that atleast some galaxies formed essentially monolithically, with high star-formationrates sustained over a few 10^8 years, and without the aid of major mergers.Comment: 25 pages, 13 figures, accepted to Ap