Deep HST/PC Images of a Young Radio Galaxy at z=2.390

Abstract

We present deep 63-orbit HST/PC images at ~0.06" FWHM resolution in the filters B_450, V_606 & I_814 - as well as in redshifted Lya - of the radio source LBDS 53W002, a compact narrow-line galaxy at z=2.390. These images allow us to distinguish several morphological components: (1) an unresolved nuclear point source (<=500 pc at z=2.390 for Ho=75, qo=0), likely the central AGN which contains <=20-25% of the total light in BVI; (2) a compact continuum core (re~0.05"); (3) a more extended envelope with an r^1/4-like light-profile and re~0.25" (~2 kpc); (4) two blue ''clouds'' roughly colinear across the nucleus aligned with the radio source axis and contained well within the size of the radio source. (B-I) color maps may suggest a narrow dust lane crossing between the nucleus and the smaller blue cloud. The radio source is not smaller than the distance between the blue continuum clouds, and coincides with a bright Lya ''arc'' in the western cloud, suggesting that jet-induced star-formation could cause both blue clouds, except the outer parts of the western cloud. The shape of this larger blue cloud suggests reflected AGN continuum-light shining through a cone (plus re-radiated Lya in emission). The OVRO interferometric CO-detection (Scoville et al. 1997) on both sides of 53W002 - and in the same direction as the continuum clouds and the radio jet - also suggest a star-bursting region induced by its radio jet, at least in the inner parts. Even at radio powers ~1.5 dex fainter than the 3CR sources, we thus find many of the same aligned features and complex morphology, although at much smaller angular scales and lower optical-UV luminosities. We discuss the consequences for 53W002's formation in the context of the 16 sub-galactic objects at z~2.40 around 53W002 (Pascarelle et al. 1996).