Abstract
We present images and long-slit spectra obtained with FORS1 at UT1 of the VLT centered on the gravitational arc of the galaxy cluster 1E0657-56 (z =0 :296). The cluster is one of the hottest, most massive clusters known so far and acts as a powerful gravitational telescope, amplifying the flux of background sources by up to a factor of 20. We present photometric results together with the spectra of the gravitational arc (z =3 :24) and four additional amplied high redshift objects (z =2 :34 to 3.08) that were also included in the slit by chance coincidence. A magnication map has been obtained from a lens model derived from the multiple image systems. We compare our observed spectra with models and briefly discuss the stellar contents of these galaxies. Furthermore we measured the equivalent widths of the C iv 1550 and Si iv 1400 absorption lines for the objects behind 1E0657-56 studied here, as well as for some additional starburst galaxies (nearby and at high z). For C iv we nd an increasing absorption equivalent width with decreasing redshift. We discuss whether this correlation could be related to the increase of metallicity with the age of the universe.
Highlights
In the recent years the technique pioneered by Steidel & Hamilton (1992, 1993) of deep imaging to identify U- and B-drop-out objects has been extremely successful in finding high-redshift galaxies
We present images and long-slit spectra obtained with FORS1 at UT1 of the VLT centered on the gravitational arc of the galaxy cluster 1E0657-56 (z = 0.296)
We present photometric results together with the spectra of the gravitational arc (z = 3.24) and four additional amplified high redshift objects (z = 2.34 to 3.08) that were included in the slit by chance coincidence
Summary
In the recent years the technique pioneered by Steidel & Hamilton (1992, 1993) of deep imaging to identify U- and B-drop-out objects has been extremely successful in finding high-redshift galaxies. Based on observations obtained with FORS at Paranal at UT1 of the VLT Spectacular examples of such studies are the pair of z = 4.92 objects in the field of CL 1358+62 (Franx et al 1997), the gravitational fold arc galaxy cB 58 (Seitz et al 1998; Carlberg et al 1996) which shows the features of a classical Lyman break object (Pettini et al 2000), the arcs in A2390 (Frye & Broadhurst 1998; Pello et al 1999), the star-forming galaxy in A2218 (Ebbels et al 1996.) Here we report on five high-redshift, gravitationally lensed objects we have found in the background of the cluster 1E0657-56. Except for the arc and the core we used the 3 -aperture colors to determine the photometric redshifts of the observed objects. We see that the photometric redshifts (see Table 1) are in good agreement with those derived from the spectra
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