Outer-disk reddening and gas-phase metallicities

The CALIFA connection

R. A. Marino, A. Gil De Paz, S. F. Sánchez, P. Sánchez-Blázquez, N. Cardiel, A. Castillo-Morales, S. Pascual, J. Vílchez, C. Kehrig, M. Mollá, J. Mendez-Abreu, C. Catalán-Torrecilla, E. Florido, I. Perez, T. Ruiz-Lara, S. Ellis, A. R. López-Sánchez, R. M. González Delgado, A. De Lorenzo-Cáceres, R. García-Benito & 10 others L. Galbany, S. Zibetti, C. Cortijo, V. Kalinova, D. Mast, J. Iglesias-Páramo, P. Papaderos, C. J. Walcher, J. Bland-Hawthorn, Califa Team

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Abstract

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 ≤1010 M′ 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.

Original languageEnglish
Article numberA47
Pages (from-to)1-29
Number of pages29
JournalAstronomy and Astrophysics
Volume585
DOIs
Publication statusPublished - 1 Jan 2016

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Keywords

  • Galaxies: abundances
  • Galaxies: evolution
  • Galaxies: ISM
  • Galaxies: photometry
  • Hii regions
  • ISM: abundances

Cite this

Marino, R. A., Gil De Paz, A., Sánchez, S. F., Sánchez-Blázquez, P., Cardiel, N., Castillo-Morales, A., ... Team, C. (2016). Outer-disk reddening and gas-phase metallicities: The CALIFA connection. Astronomy and Astrophysics, 585, 1-29. [A47]. https://doi.org/10.1051/0004-6361/201526986