J. D. Kurk — Page 3

arXiv2000

Search for clusters at high redshift - I. Candidate Lya emitters near 1138-262 at z=2.2

Radio, optical and X-ray observations of the powerful radio galaxy PKS 1138-262 at z=2.156 have suggested that this galaxy is a massive galaxy in the center of a forming cluster. We have imaged 1138-262 and the surrounding 38 square arcminute field with the Very Large Telescope in a broad band and a narrow band encompassing the redshifted Lya emission. We detect 50 objects with rest equivalent width larger than 20 A and a luminous, highly extended Lya halo around 1138-262. If the radio galaxy is at the center of a forming cluster, these objects are candidate Lya emitting cluster galaxies.

astro-ph↗

arXiv2000

A vestige low metallicity gas shell surrounding the radio galaxy 0943-242 at z=2.92

Observations are presented showing the doublet CIV 1550 absorption lines superimposed on the CIV emission in the radio galaxy 0943-242. Within the errors, the redshift of the absorption system that has a column density of N_CIV = 10^{14.5 +- 0.1} cm-2 coincides with that of the deep Ly-alpha absorption trough observed by Rottgering et al. (1995). The gas seen in absorption has a resolved spatial extent of at least 13 kpc (the size of the extended emission line region). We first model the absorption and emission gas as co-spatial components with the same metallicity and degree of excitation. Using the information provided by the emission and absorption line ratios of CIV and Ly-alpha, we find that the observed quantities are incompatible with photoionization or collisional ionization of cloudlets with uniform properties. We therefore reject the possibility that the absorption and emission phases are co-spatial and favour the explanation that the absorption gas has low metallicity and is located further away from the host galaxy (than the emission line gas). The estimated low metallicity for the absorption gas in 0943-242 (Z \~ 1% solar) and its proposed location -outer halo outside the radio cocoon- suggest that its existence preceeds the observed AGN phase and is a vestige of the initial starburst at the onset of formation of the parent galaxy.

astro-ph↗

arXiv1999

Deep Lyman alpha imaging of radio galaxy 1138-262 at redshift 2.2

Observations of the powerful radio galaxy 1138-262 at z=2.2 suggest that this galaxy is a massive galaxy in the center of a forming cluster. We have imaged the field of 1138-262 with the Very Large Telescope in a narrow band encompassing the redshifted Lyman alpha emission. We detect 34 probable line emitters in the 6'x6' field. These are candidate Lyman alpha emitting galaxies in the supposed cluster. The observations also reveal that the radio galaxy is enclosed by a very extended Lyman alpha halo (160 kpc).

astro-ph↗