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Astron. Astrophys. 359, 953-959 (2000)

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EROs in the EIS fields

I. The AXAF (Chandra) deep field *

M. Scodeggio  ** and D.R. Silva

European Southern Observatory, Karl-Schwarzschild-Strasse 2 85748 Garching bei München, Germany (marcos@ifctr.mi.cnr.it, mscodegg,dsilva@eso.org)

Received 28 May 1999 / Accepted 14 April 2000


The publicly available EIS-DEEP optical-NIR data for the AXAF (Chandra) Deep Field have been used to construct samples of Extremely Red Objects (EROs) using various single-band and multi-band color criteria. In this work we define as EROs objects with colors consistent with passively evolving elliptical galaxies at [FORMULA] 1. The EROs surface densities we derive are intermediate between previous published values, emphasizing again the need for larger survey areas to constrain the effects of possible large-scale structure. Although various single-color selected samples can be derived, the EROs sample selected using [FORMULA] jointly is likely to contain the highest fraction of passively evolving luminous field elliptical galaxies at [FORMULA]1, or conversely, the lowest fraction of lower redshift interlopers. The surface density of this multi-band selected EROs sample is consistent with the conclusion that little or no field elliptical volume density evolution has occurred in the redshift range 0 [FORMULA] 1.5. However, extensive spectroscopic followup is necessary to confirm this conclusion.

Key words: galaxies: elliptical and lenticular, cD – galaxies: evolution – galaxies: formation – cosmology: observations

* Based on observations collected at the European Southern Observatory, La Silla, Chile; ESO programs No. 61.A-9005 and 162.O-0917
** Current address: Istituto di Fisica Cosmica "G. Occhialini", via Bassini 15, 20133 Milano, Italy

Send offprint requests to: Marco Scodeggio

© European Southern Observatory (ESO) 2000

Online publication: July 13, 2000