Astronomy and Astrophysics, volume 585A, 47-47 (2016/1-1)
Outer-disk reddening and gas-phase metallicities: The CALIFA connection.
MARINO R.A., GIL DE PAZ A., SANCHEZ S.F., SANCHEZ-BLAZQUEZ P., CARDIEL N., CASTILLO-MORALES A., PASCUAL S., VILCHEZ J., KEHRIG C., MOLLA M., MENDEZ-ABREU J., CATALAN-TORRECILLA C., FLORIDO E., PEREZ I., RUIZ-LARA T., ELLIS S., LOPEZ-SANCHEZ A.R., GONZALEZ DELGADO R.M., DE LORENZO-CACERES A., GARCIA-BENITO R., GALBANY L., ZIBETTI S., CORTIJO C., KALINOVA V., MAST D., IGLESIAS-PARAMO J., PAPADEROS P., WALCHER C.J., BLAND-HAWTHORN J. (The CALIFA Team)
Abstract (from CDS):
We study, for the first time in a statistically significant and well-defined sample, the relation between the outer-disk ionized-gas metallicity gradients and the presence of breaks in the surface brightness profiles of disk galaxies. Sloan Digital Sky Survey (SDSS) g'- and r'-band surface brightness, (g'-r') color, and ionized-gas oxygen abundance profiles for 324 galaxies within the Calar Alto Legacy Integral Field Area (CALIFA) survey are used for this purpose. We perform a detailed light-profile classification, finding that 84% of our disks show down- or up-bending profiles (Type II and Type III, respectively), while the remaining 16% are well fitted by one single exponential (Type I). The analysis of the color gradients at both sides of this break shows a U-shaped profile for most Type II galaxies with an average minimum (g'-r') color of ∼0.5mag and an ionized-gas metallicity flattening associated with it only in the case of low-mass galaxies. Comparatively, more massive systems show a rather uniform negative metallicity gradient. The correlation between metallicity flattening and stellar mass for these systems results in p-values as low as 0.01. Independent of the mechanism having shaped the outer light profiles of these galaxies, stellar migration or a previous episode of star formation in a shrinking star-forming disk, it is clear that the imprint in their ionized-gas metallicity was different for low- and high-mass Type II galaxies. In the case of Type III disks, a positive correlation between the change in color and abundance gradient is found (the null hypothesis is ruled out with a p-value of 0.02), with the outer disks of Type III galaxies with masses ≤1010M☉ showing a weak color reddening or even a bluing. This is interpreted as primarily due to a mass downsizing effect on the population of Type III galaxies that recently experienced an enhanced inside-out growth.
galaxies: abundances - galaxies: evolution - galaxies: photometry - galaxies: ISM - ISM: abundances - HII regions
VizieR on-line data:
<Available at CDS (J/A+A/585/A47): tableb1.dat tableb2.dat>
Tables B.1 and B.2 : SDSSJ 100141 is SDSS J100141.02+371447.4.
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