Extended Lyman-α emission in 3C 326.1 - A 100 kiloparsec cloud of ionized gas at a redshift of 1.82

Abstract

We report the discovery of a large cloud of ionized gas associated with the high-redshift radio source 3C 326.1 New radio-frequency images made at 4.9 GHz and 15 GHz with the Very Large Array show the radio source to be a small double (~ 7") without a detectable core at the level of ~ 0.5 mJy. Long-slit spectrograms and Lγa imaging reveal a ~ 100 kpc diameter cloud of ionized gas with a redshift of 1.825 encompassing the radio source. Deep broad-band images show two faint (V = 23.5-24.5) blue objects located on the periphery of the cloud, as well as some very faint (V = 25-26) extremely blue diffuse objects roughly coincident with the brightest regions of the cloud. Long-slit CCD spectra suggest that the Lγa emission from the cloud has a large intrinsic width (FWHM ≈ 1000 km s^(-1)). Spectra taken in the red show weak extended emission from C II] and C III], but C IV emission has not been detected. The large equivalent width of Lγa and the relative strengths of the carbon lines are consistent with H n region-type photoionization. We tentatively propose that 3C 326.1 is a young and/or forming galaxy.