How was the Hubble sequence 6 Gyrs ago - Astrophysics > Cosmology and Nongalactic AstrophysicsReport as inadecuate

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Abstract: The way galaxies assemble their mass to form the well-defined Hubble sequenceis amongst the most debated topic in modern cosmology. One difficulty is tolink distant galaxies to those at present epoch. We aim at establishing howwere the galaxies of the Hubble sequence, 6 Gyrs ago. We intend to derive apast Hubble sequence that can be causally linked to the present-day one. Weselected samples of nearby galaxies from the SDSS and of distant galaxies fromthe GOODS survey. We verified that each sample is representative of galaxies.We further showed that the observational conditions necessary to retrieve theirmorphological classification are similar in an unbiased way. Morphologicalanalysis has been done in an identical way for all galaxies in the two samples.We found an absence of number evolution for elliptical and lenticular galaxies,which strikingly contrasts with the strong evolution of spiral and peculiargalaxies. Spiral galaxies were 2.3 times less abundant in the past, that isexactly compensated by the strong decrease by a factor 5 of peculiar galaxies.It strongly suggests that more than half of the present-day spirals hadpeculiar morphologies, 6 Gyrs ago, and this has to be accounted by any scenarioof galactic disk evolution and formation. The past Hubble sequence can be usedto test these scenarios as well as to test evolution of fundamental planes forspirals and bulges.

Author: R. Delgado-Serrano 1,2, F. Hammer 1, Y. B. Yang 1,3, M. Puech 1, H. Flores 1, M. Rodrigues 1 1 GEPI, Paris Observatory, CNRS, Uni



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