Premature dismissal of high-redshift elliptical galaxies

High - redshift elliptical galaxies : are they ( all ) really compact ?

We investigate the properties of 12 ultramassive passively evolving early-type galaxies (ETGs) at zphot > 1.4 in the COSMOS 2 deg2 field. These 12 ETGs were selected as pBzKs, have accurate 1.4 zphot 1.7, high Sérsic index profiles typical of ellipticals, no detection at 24μm, resulting in a complete ETG sample at M∗ > 2.5 × 1011 M (Chabrier initial mass function). Contrary to the previous clai...

NICMOS observations of high redshift radio galaxies : witnessing the formation of bright elliptical galaxies ?

We present the results of a near infrared imaging program of a sample of 19 radio galaxies with redshift between 1.7 and 3.2, using the NICMOS Camera 2 on the Hubble Space Telescope. The galaxies were observed in H-band which, for 18 of the 19 targets, samples the rest-frame optical emission longwards of the 4000Å break. For many sources this band contains emission lines, but we estimated that ...

Morphological Evolution in High Redshift Radio Galaxies and the Formation of Giant Elliptical Galaxies

We present deep near–infrared images of high redshift radio galaxies (HzRGs) obtained with the Near Infrared Camera (NIRC) on the Keck I telescope. In most cases, the near–IR data sample rest wavelengths free of contamination from strong emission lines and at λrest > 4000Å, where older stellar populations, if present, might dominate the observed flux. At z > 3, the rest–frame optical morphologi...

Galaxies at High Redshift

Galaxies at High Redshift

Within just the last few years, we have advanced from knowing only a few galaxies at z > 2 to having redshifts for nearly 1000 z ∼ 2–5 objects. The majority of this sample has been detected through the photometric “dropout” technique used so successfully by Steidel and his collaborators. In addition, a handful of objects have already been detected at z > 5, and we may already have a few objects...