Near-Infrared Observations of Powerful High-Redshift Radio Galaxies: 4C 40.36 and 4C 39.37

We present near-infrared imaging and spectroscopic observations of two FR IIhigh-redshift radio galaxies (HzRGs), 4C 40.36 (z=2.3) and 4C 39.37 (z=3.2),obtained with the Hubble, Keck, and Hale Telescopes. High resolution imageswere taken with filters both in and out of strong emission lines, and togetherwith the spectroscopic data, the properties of the line and continuum emissionswere carefully analyzed. Our analysis of 4C 40.36 and 4C 39.37 shows thatstrong emission lines (e.g., [O III] 5007 A and H alpha+[N II]) contribute tothe broad-band fluxes much more significantly than previously estimated (80%vs. 20-40%), and that when the continuum sources are imaged through line-freefilters, they show an extremely compact morphology with a high surfacebrightness. If we use the R^1/4-law parametrization, their effective radii(r(e)) are only 2-3 kpc while their restframe B-band surface brightnesses atr(e) are I(B) ~ 18 mag/arcsec^2. Compared with z ~ 1 3CR radio galaxies, theformer is x3-5 smaller, while the latter is 1-1.5 mag brighter than what ispredicted from the I(B)-r(e) correlation. Although exponential profiles produceequally good fits for 4C 40.36 and 4C 39.37, this clearly indicates that withrespect to the z~1 3CR radio galaxies, the light distribution of these twoHzRGs is much more centrally concentrated. Spectroscopically, 4C 40.36 shows aflat (fnu=const) continuum while 4C 39.37 shows a spectrum as red as that of alocal giant elliptical galaxy. Although this difference may be explained interms of a varying degree of star formation, the similarities of their surfacebrightness profiles and the submillimeter detection of 4C 39.37 might suggestthat the intrinsic spectra is equally blue (young stars or an AGN), and thatthe difference is the amount of reddening.Comment: 30 pages, 6 tables, 10 figures; Accepted for publication in Astronomical Journa