Astron. Astrophys. 351, 433-441 (1999)

Lensed galaxies in Abell 370

II. The ultraviolet properties of arclets and the star formation rate at high redshift ^*

J. Bézecourt ¹, G. Soucail ², R.S. Ellis ³ and J-P. Kneib <sup>2

1</sup> Kapteyn Institute, Postbus 800, 9700 AV Groningen, The Netherlands
² Observatoire Midi-Pyrénées, Laboratoire d'Astrophysique, UMR 5572, 14 Avenue E. Belin, 31400 Toulouse, France
³ Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK

Received 2 September 1999 / Accepted 29 September 1999

Abstract

We discuss the statistical properties of faint background galaxies detected in a deep Hubble Space Telescope ultraviolet (F336W) Wide Field Planetary Camera 2 image of the lensing cluster Abell 370 (z=0.37). By combining modelled field galaxy counts at this wavelength with a detailed mass model for the cluster, we develop techniques for predicting the expected redshift distribution of lensed sources and find the bulk of the sources should be moderately magnified sources whose redshifts lie between 0.5 and 2. We compare these predictions with redshift estimates derived from the lens inversion method which utilises the shapes of individual arclets in the context of a known field ellipticity distribution. This allows us to infer the comoving star formation rate for the range where there is currently little spectroscopic data. We discuss our results in the context of contemporary pictures for the history of star formation.

Key words: galaxies: clusters: individual: Abell 370 galaxies: evolution galaxies: starburst cosmology: observations cosmology: gravitational lensing

* Based on observations with the NASA/ESA Hubble Space Telescope obtained from the data archive at the Space Telescope Science Institute, USA

Send offprint requests to: J. Bézecourt (bezecour@astro.rug.nl)

© European Southern Observatory (ESO) 1999

Online publication: November 3, 1999

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