The manifold spectra and morphologies of EROs

Free access article

Issue		A&A Volume 412, Number 1, December II 2003


Page(s)		L1 - L5
Section		Letters
DOI		http://dx.doi.org/10.1051/0004-6361:20031601

A&A 412, L1-L5 (2003)
DOI: 10.1051/0004-6361:20031601

Letter

The manifold spectra and morphologies of EROs

A. Cimatti¹, E. Daddi², P. Cassata³, E. Pignatelli⁴, G. Fasano⁴, J. Vernet¹, E. Fomalont⁵, K. Kellermann⁵, G. Zamorani⁶, M. Mignoli⁶, L. Pozzetti⁶, A. Renzini², S. di Serego Alighieri¹, A. Franceschini³, E. Giallongo⁷ and A. Fontana⁷

¹ INAF - Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
² European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
³ Dipartimento di Astronomia, Università di Padova, Vicolo dell'Osservatorio, 2, 35122 Padova, Italy
⁴ INAF - Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio, 5, 35122 Padova, Italy
⁵ National Radio Astronomy Observatory, Charlottesville, VA 22903, USA
⁶ INAF - Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
⁷ INAF - Osservatorio Astronomico di Roma, via dell'Osservatorio 2, Monteporzio, Italy

(Received 3 July 2003 / Accepted 13 October 2003)

Abstract
Deep VLT optical spectroscopy, HST+ACS (GOODS) imaging and VLA observations are used to unveil the nature of a complete sample of 47 EROs with $R-K_{\rm s}>5$ and $K_{\rm s}<20$ . The spectroscopic redshift completeness is 62%. Morphological classification was derived for each ERO through visual inspection and surface brightness profile fitting. Three main ERO morphological types are found: E/S0 galaxies ( $\sim$ 30-37%), spiral-like (~ 24-46%) and irregular systems (~ 17-39%). The only ERO detected in the radio is likely to host an obscured AGN. The average radio luminosity of the star-forming EROs undetected in the radio implies star formation rates of the order of ~33 $M_{\odot}$ yr ^-1. The colors, redshifts and masses of the E/S0 galaxy subsample imply a minimum formation redshift $z_{\rm f}\sim 2$ . With this $z_{\rm f}$ there is enough time to have old and massive stellar spheroids already assembled at $z\sim 1$ . We verify that the $R-K_{\rm s}$ vs. $J-K_{\rm s}$ color diagram is efficient in segregating old and dusty-star-forming EROs.

Key words: galaxies: evolution -- galaxies: elliptical and lenticular, cD -- galaxies: starbust -- galaxies: formation

Offprint request: A. Cimatti, cimatti@arcetri.astro.it

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.