Isolated-galaxies：residual-of-primordial-building-blocks？.pdfVIP

c Astronomy Astrophysics manuscript no. ms ESO 2006 May 16, 2006 Isolated galaxies: residual of primordial building blocks? 1 1 2 3 2 G. Galletta , G. Rodighiero , D. Bettoni , M. Moles , and J. Varela 1 Dipartimento di Astronomia, Universit`a di Padova, Vicolo dell’Osservatorio 2, I-35122, Padova e-mail: giuseppe.galletta@unipd.it, e-mail: rodighiero@pd.astro.it 2 INAF - Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122, Padova e-mail: bettoni@pd.astro.it, e-mail: jesus.varela@oapd.inaf.it 3 Instituto de Astrof´ısica de Andaluc´ıa (C.S.I.C.) Apartado 3004, 18080 Granada, Spain e-mail: moles@iaa.es Received ; accepted ABSTRACT Context. The mass assembly is believed to be the dominant process of early galaxy formation. This mechanism of galaxy building can proceed either by repeated major mergers with other systems, or by means of accretion of matter from the surrounding regions. Aims. In this paper we compare the properties of local disk galaxies that appear isolated, i.e. not tidally affected by other galaxies during the last few Gyr within the volume given by cz ≤ 5000 km s−1, with those galaxies at z values from 0.25 to 5. Methods. Effective radii for 203 isolated galaxies and 1645 galaxies from the RC3 have been collected and the two samples have been analyzed statistically. A similar comparison has been made with half light radii studied at high z from the literature. Results. We found that isolated galaxies are in general smaller than other present