Deep [ITAL]Hubble Space Telescope[/ITAL]/Planetary Camera Imaging of a Young Compact Radio Galaxy at [CLC][ITAL]z[/ITAL][/CLC] = 2.390

Abstract

We present deep 63-orbit Hubble Space Telescope/Planetary Camera images at ~006 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 (re 005); (3) a more extended envelope with an r1/4-like light profile and re 025 (~2 kpc); (4) two blue 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 z2.40 around 53W002 (Pascarelle et al.).