EDP Sciences
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Volume 380, Number 2, December III 2001
Page(s) 425 - 434
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20011409

A&A 380, 425-434 (2001)
DOI: 10.1051/0004-6361:20011409

New insights on the accuracy of photometric redshift measurements

M. Massarotti1, 2, A. Iovino2, A. Buzzoni2, 3 and D. VallsGabaud4

1  Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy
2  Osservatorio Astronomico di Brera, Via Brera 28, 20121 Milano, Italy
    e-mail: iovino@brera.mi.astro.it
3  Telescopio Nazionale Galileo, PO Box 565, 38700 Santa Cruz de La Palma (TF), Spain
    e-mail: buzzoni@tng.iac.es
4  CNRS UMR 5572, Observatoire Midi-Pyrénées, 14 Av. E. Belin, 31400 Toulouse, France
    e-mail: dvg@ast.obs-mip.fr

(Received 2 July 2001 / Accepted 4 October 2001 )

We use the deepest and most complete redshift catalog currently available (the Hubble Deep Field (HDF) North supplemented by new HDF South redshift data) to minimize residuals between photometric and spectroscopic redshift estimates. The good agreement at zspec < 1.5 shows that model libraries provide a good description of the galaxy population. At $z_{spec} \geq 2.0$, the systematic shift between photometric and spectroscopic redshifts decreases when the modeling of the absorption by the interstellar and intergalactic media is refined. As a result, in the entire redshift range $z \in [0, 6]$, residuals between photometric and spectroscopic redshifts are roughly halved. For objects fainter than the spectroscopic limit, the main source of uncertainty in photometric redshifts is related to photometric errors, and can be assessed with Monte Carlo simulations.

Key words: galaxies: distances and redshifts, evolution, ISM, intergalactic medium -- methods: data analysis -- techniques: photometric

Offprint request: M. Massarotti, massarot@brera.mi.astro.it

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© ESO 2001