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For refcode 1999ApJ...516...62D:
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1999ApJ...516...62D Chemical Evidence for Morphological Evolution of Spiral Galaxies YVAN DUTIL AND JEAN-RENE ROY Dipartement de Physique and Observatoire du Mont Megantic, Universite Laval, Quebec G1K 7P4, Canada; dutil, jrroy@phy.ulaval.ca Received 1998 August 12; accepted 1998 December 8 ABSTRACT Using the methods of spectrophotometric imagery and multislit spectroscopy, we have derived the radial abundance profiles from O/H measurements in 549 H II regions of eight early-type spiral galaxies. We then compared the characteristic abundance levels and radial distributions of this group of spirals with those of late-type galaxies. The early-type galaxies of our sample display gradients that are flatter and overall levels of O/H abundances that are higher than those of normal late-type galaxies. Early-type galaxies show an identical trend in the behavior of extrapolated central abundance versus morphological type to that shown by late-type galaxies with strong bars, even in the absence of a bar. On a diagram showing extrapolated central abundances versus morphological types, two clearly separated sequences appear: late-type barred galaxies and early-type (barred or unbarred) galaxies clearly fall on a sequence ~0.5 dex in abundance below that of normal late-type galaxies. This behavior is consistent with a scenario of morphological evolution of disk galaxies by the formation and dissolution of a bar over a period of a few 10^9^ yr, where later type galaxies (Sd, Sc, Sbc) evolve into earlier-type disk galaxies (Sb, Sa) through transitory SBc and SBb phases. Subject headings: galaxies: abundances-galaxies: evolution-galaxies: ISM- galaxies: spiral-galaxies: structure
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