IMAGES^*,**

II. A surprisingly low fraction of undisturbed rotating spiral disks at z ~ 0.6 The morpho-kinematical relation 6 Gyr ago

¹ GEPI, Observatoire de Paris, CNRS, University Paris Diderot, 5 Place Jules Janssen, 92195 Meudon, France e-mail: benoit.neichel@obspm.fr
² ESO, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
³ Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune 411007, India
⁴ IFARHU-SENACYT, Technological University of Panama, 0819-07289 Panama, Rep. of Panama
⁵ Laboratoire d'Astrophysique de Marseille, Observatoire Astronomique de Marseille-Provence, 2 Place Le Verrier, 13248 Marseille, France
⁶ MPIA, Königstuhl 17, 69117 Heidelberg, Germany
⁷ Centre de Recherche Astronomique de Lyon, 9 Avenue Charles Andr, 69561 Saint-Genis-Laval Cedex, France
⁸ National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100012, PR China
⁹ Stockholm Observatory, AlbaNova University Center, Stockholms Center for Physics, Astronomy and Biotechnology, Roslagstullsbacken 21, 10691 Stockholm, Sweden
¹⁰ INAF – Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
¹¹ Department of Physics, University of Calicut, Kerala 673635, India
¹² INAF, Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Florence, Italy

¹³ IASF-INAF, via Bassini 15, 20133 Milano, Italy

Received: 10 December 2007
Accepted: 12 March 2008

Abstract

We present a first combined analysis of the morphological and dynamical properties for the intermediate-mass Galaxy Evolution Sequence (IMAGES) sample. It is a representative sample of 52  galaxies with M_stell from 1.5 to that possesses 3D resolved kinematics and HST deep imaging in at least two broad band filters. We aim at evaluating the evolution of rotating spirals robustly since , as well as at testing the different schemes for classifying galaxies morphologically. We used all the information provided by multi-band images, color maps, and 2D light fitting to assign a morphological class to each object. We divided our sample into spiral disks, peculiar objects, compact objects, and mergers. Using our morphological classification scheme, 4/5 of the identified spirals are rotating disks, and more than 4/5 of identified peculiar galaxies show complex kinematics, while automatic classification methods such as concentration-asymmetry and GINI-M20 severely overestimate the fraction of relaxed disk galaxies. Using this methodology, we find that the fraction of undisturbed rotating spirals has increased by a factor ~2 during the past 6 Gyr, a much higher fraction than was found previously based on morphologies alone. These rotating spiral disks are forming stars very rapidly, even doubling their stellar masses over the past 6 Gyr, while most of their stars were formed a few Gyr earlier, which reveals a large gas supply. Because they are the likely progenitors of local spirals, we can conjecture how their properties are evolving. Their disks show some evidence of inside-out growth, and the gas supply/accretion is not random since the disk needs to be stable in order to match the local disk properties.