Deep Hubble Space Telescope/Planetary Camera Imaging of a Young Compact Radio Galaxy at Z = 2.390

Abstract

We present deep 63-orbit Hubble Space Telescope/Planetary Camera images at ~0.06" FWHM resolution in the filters B₄₅₀, V₆₀₆, and I₈₁₄--as well as in redshifted Lyα--of the radio source 53W002, a compact narrow-line galaxy at z=2.390 from the Leiden-Berkeley Deep Survey. These images allow us to distinguish several morphological components: (1) an unresolved nuclear point source (<~500 pc at z=2.390 for H₀=75, q₀=0), likely the central active galactic nucleus (AGN) that contains <~20%-25% of the total light in BVI; (2) a compact continuum core (r_e ~= 0.05") (3) a more extended envelope with an r^1/4-like light profile and r_e ~= 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. The (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 Lyα ``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 reradiated Lyα in emission). The Owens Valley Radio Observatory interferometric CO detection (Scoville et al.) on both sides of 53W002--and in the same direction as the continuum clouds and the radio jet--also suggests a star-bursting region induced by its radio jet, at least in the inner parts. Hence, both mechanisms likely play a role in the ``alignment effect.'' 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 subgalactic objects at z~=2.40 around 53W002 (Pascarelle et al.).

Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.