Astronomy and Astrophysics, volume 346, 359-368 (1999/6-2)
Two multiple-imaged z = 4.05 galaxies in the cluster-lens Abell 2390.
PELLO R., KNEIB J.P., LE BORGNE J.F., BEZECOURT J., EBBELS T.M., TIJERA I., BRUZUAL G., MIRALLES J.M., SMAIL I., SOUCAIL G. and BRIDGES T.J.
Abstract (from CDS):
We present the first results on the identification and study of very distant field galaxies in the core of cluster-lenses, using a selection criterium based on both lens modelling and photometric redshifts. We concentrate on two multiple-imaged sources at z=4.05 in the cluster Abell 2390. The two objects presented in this paper, namely H3 (cusp arc) and H5 (fold arc), were identified through lens modelling as multiple images of high-redshift sources at z≳3.5 (Kneib et al., 1999, in prep.). We confirm the excellent agreement between this identification and both their photometric redshifts and morphologies. Our CFHT/WHT program for a systematic redshift survey of arcs in clusters has allowed to obtain a set of spectra on three different images at z∼4 : the brightest image of H3, whose redshift was already confirmed by Frye & Broadhurst (1998ApJ...499L.115F
), and the two brightest images of H5. The later is then confirmed spectroscopically as a multiple image, giving a strong support to the lens model. The main feature in each of these spectra is a strong emission line, identified as Ly α, leading to z=4.05 for both H3 and H5. The spectrophotometric properties of these galaxies are studied, in particular the degeneracy in the parameter-space defined by the SFR type, age, metallicity and reddening. H3 and H5 are intrinsically bright and clumpy galaxies (M*B
-2 magnitudes), located ∼100h–150
kpc apart on the source plane, with mean metallicities compatible with a fraction of solar or even solar values. These results seem to favour a hierarchical merging scenario, where we are seeing a relatively evolved phase in these two z∼4 objects, with stars forming locally and efficiently.
galaxies: clusters: general - galaxies: clusters: individual: - cosmology: observations - cosmology: dark matter - cosmology: gravitational lensing
Fig.1: [PKL99] ACO 2390 HN (Nos H3, H5), [PKL99] ACO 2390 HNa (Nos H3a-H3c, H5a-H5b).
Status at CDS:
Kneib+ 1999 not published in 2005, H3 and H5 are designated as [PKL99] objects.
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