Further Multiwavelength Observations of the Ssa 22 Ly Α Emitting ‘ Blob ’

We present new follow-up observations of the sub-mm luminous Ly α-emitting object in the SSA22 z = 3.09 galaxy overdensity, referred to as 'Blob 1' by Steidel et al. (2000). In particular we discuss high resolution Hubble Space Telescope optical imaging, Owens Valley Radio Observatory spectral imaging, Keck spectroscopy, VLA 20 cm radio continuum imaging, and Chandra X-ray observations. We also present a more complete analysis of the existing James Clerk Maxwell Telescope sub-mm data. We detect several optical continuum components which may be associated with the core of the submillimeter emitting region. A radio source at the position of one of the HST components (22:17:25.94, +00:12:38.9) identifies it as the likely counterpart to the submillimeter source. We also tentatively detect the CO(4– 3) molecular line, centered on the radio position. We use the CO(4–3) intensity to estimate a limit on the gas mass for the system. The optical morphology of sources within the Ly α cloud appears to be filamentary, while the optical source identified with the radio source has a dense knot which may be an AGN or compact starburst. We obtain a Keck-LRIS spectrum of this object, despite its faintness (R = 26.8). The spectrum reveals weak Lyα emission, but no other obvious features, suggesting that the source is not an energetic AGN (or that it is extremely obscured). We use non-detections in deep Chandra X-ray images to constrain the nature of the 'Blob'. Although conclusive evidence regarding the nature of the object remains hard to obtain at this redshift, the evidence presented here is at least consistent with a dust-obscured AGN surrounded by a starburst situated at the heart of this giant Ly α cloud. Deep surveys of the submillimeter (sub-mm) sky using the Submillimeter Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope have uncovered a population of distant dust-rich galaxies (see Blain et al. 2002 and references therein). Based on the radio/sub-mm indices, optical colors, and the spectro-scopic identifications for > 60 submillimeter galaxies, the majority of these systems are thought to lie at redshifts of z ∼ 1–4 (e.g. Smail et al. 2002, Chapman et al. 2003a, 2004). Identifying the counterparts of sub-mm sources at other wavelengths has proven difficult, due to the large beam-size of sub-mm instruments, and the inherent faintness of the sources at all shorter wavelengths. The radio regime has emerged as an efficient means to pinpoint the sub-mm …