[Previous] | [Session 73] | [Next]
E. Egami (Caltech), L. Armus (SIRTF/SSC), G. Neugebauer, T.W. Murphy Jr., B.T. Soifer, K. Matthews (Caltech), A.S. Evans (SUNY)
We present near-IR imaging and spectroscopic observations of two FR~II high-redshift radio galaxies (HzRGs), 4C~40.36 (z=2.27) and 4C~39.37 (z=3.22), obtained with the Hubble, Keck, and Hale Telescopes. The HST/NICMOS images taken with the line-free filters show a compact and symmetric continuum source in both galaxies. Their surface brightness profiles can be fit equally well by either an R1/4- or exponential-law profile, indicating that these two types of profiles cannot easily be distinguished for z>2 HzRGs even with the HST/NICMOS images. If we adopt the R1/4-law fits, the half-light radii are only a few kpc, significantly smaller than those of z ~1 radio galaxies (~10 kpc). Spectroscopically, our Keck near-IR spectra show that 4C~40.36 has an extremely flat continuum spectrum (f\nu = const) while the spectrum of 4C~39.37 is as red as that of a gE galaxy. These results indicate that at z>2, we are seeing a substantial size/spectral evolution of the near-IR (i.e., restframe visual) continuum sources in HzRGs, despite which the K-z relation is somehow maintined.