Optical and Near-Infrared Color Profiles in Nearby Early-Type Galaxies and The Implied Age and Metallicity Gradients

Hong Wu; Zhengyi Shao; H. J. Mo; Xiaoyang Xia; Zugan Deng

doi:10.1086/427821

paper

Optical and Near-Infrared Color Profiles in Nearby Early-Type Galaxies and The Implied Age and Metallicity Gradients

arXiv:astro-ph/0404226 · doi:10.1086/427821

Abstract

We present results of age and metallicity gradient analysis inferred from both optical and near-infrared surface photometry. The analysis is based on a sample of 36 nearby early-type galaxies, obtained from the Early Data Release of the Sloan Digital Sky Survey and the Two Micron All Sky Survey. Surface brightness profiles were derived in each band, and used to study the color gradients of the galaxies. Using simple stellar population models with both optical and near infrared colors, we may interpret the color gradients in term of age and metallicity gradients of galaxies. Using $g_{Z} \equiv d lo g Z_{met} / d lo g R$ and $g_{A} = d lo g Age / d lo g R$ to represent the metallicity and age gradients, we found a median value of $g_{Z} = - 0.25 \pm 0.03$ for the metallicity gradient, with a dispersion $σ_{g_{Z}} = 0.19 \pm 0.02$ . The corresponding values for the age gradient were $g_{A} = 0.02 \pm 0.04$ and $σ_{g_{A}} = 0.25 \pm 0.03$ . These results are in good agreement with recent observational results, as well as with recent simulations that suggest both monolithic collapse and major merger have played important roles in the formation of early-type galaxies. Our results demonstrate the potential of using multi-waveband colors obtained from current and future optical and infrared surveys in constraining the age and metallicity gradients of early-type galaxies.

arXiv comment40 pages, 14 figures. Revised version. Accepted by ApJ

Optical and Near-Infrared Color Profiles in Nearby Early-Type Galaxies and The Implied Age and Metallicity Gradients

Abstract

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