Letter to the Editor

The K20 survey^*

IV. The redshift distribution of galaxies: A test of galaxy formation models

¹ INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
² INAF, Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
³ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
⁴ INAF, Osservatorio Astronomico di Roma, via Dell'Osservatorio 2, Monteporzio, Italy
⁵ Dipartimento di Astronomia, Università “La Sapienza”, Roma, Italy
⁶ Racah Institute for Physics, The Hebrew University, Jerusalem, 91904 Israel
⁷ INAF, Osservatorio Astronomico di Trieste, Via G.B. Tiepolo 11, 34131 Trieste, Italy

Corresponding author: A. Cimatti, cimatti@arcetri.astro.it

Received: 12 June 2002
Accepted: 8 July 2002

Abstract

We present the redshift distribution of a complete sample of 480 galaxies with distributed over two independent fields covering a total area of 52 arcmin². The redshift completeness is 87% and 98% respectively with spectroscopic and high-quality and tested photometric redshifts. The redshift distribution of field galaxies has a median redshift , with ~32% and ~9% of galaxies at and respectively. A “blind” comparison is made with the predictions of a set of the most recent ΛCDM hierarchical merging and pure luminosity evolution (PLE) models. The hierarchical merging models overpredict and underpredict the number of galaxies at low-z and high-z respectively, whereas the PLE models match the median redshift and the low-z distribution, still being able to follow the high-z tail of . We briefly discuss the implications of this comparison and the possible origins of the observed discrepancies. We make the redshift distribution publicly available.