Stellar kinematics and populations out to 1.5 effective radii in the elliptical galaxy NGC 4636  

作　　者：Shi-Bi PU Zhan-Wen Han 

机构地区：[1]National Astronomical Observatory/Yunnan Observatory, Chinese Academy of Sciences, Kunming 650011, China [2]Graduate University of Chinese Academy of Sciences, Beijing 100049, China [3]Key Laboratory of the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, Kunming 650011, China

出　　处：《Research in Astronomy and Astrophysics》2011年第8期909-923,共15页天文和天体物理学研究（英文版）

基　　金：Supported by the National Natural Science Foundation of China rant No. 10821061;the National Basic Research Program of China (Grant Nos. 11033008 nd 2007CB815406);the pport of the Chinese Academy of Sciences (Grant No. KJCX2-YW-T24)

摘　　要：We present high quality long slit spectra along the major and minor axes out to 1.5 effective radii of the massive galaxy NGC 4636 taken by the Hobby-Eberly Telescope. Using the Fourier Correlation Quotient method, we measured the stellar line-of-sight velocity distribution along the axes. Furthermore, six Lick/IDS indices （Hβ, Mgb, Fe5015, Fe5270, Fe5335, Fe5406） are derived from the clean spectrum. By comparing the measured absorption line strengths with the predictions of Simple Stellar Population （SSP） models, we derived ages, total metallicity and a abundance profiles of the galaxy. This galaxy presents old and [α/Fe] overabundant stellar populations. Indeed, using the SSP model, we obtained the broadband color profiles. The theoretical colors match well with the measured colors and present red sharp peaks at the galaxy center. The sharp peaks of the colors are mainly shaped by the high metallicity in the galaxy＇s center. Interestingly, the galaxy has steep negative metaUicity gradients, but the trend flattens outwards. This result likely suggests that the center and outer regions of the galaxy formed through different formation processes.We present high quality long slit spectra along the major and minor axes out to 1.5 effective radii of the massive galaxy NGC 4636 taken by the Hobby-Eberly Telescope. Using the Fourier Correlation Quotient method, we measured the stellar line-of-sight velocity distribution along the axes. Furthermore, six Lick/IDS indices （Hβ, Mgb, Fe5015, Fe5270, Fe5335, Fe5406） are derived from the clean spectrum. By comparing the measured absorption line strengths with the predictions of Simple Stellar Population （SSP） models, we derived ages, total metallicity and a abundance profiles of the galaxy. This galaxy presents old and [α/Fe] overabundant stellar populations. Indeed, using the SSP model, we obtained the broadband color profiles. The theoretical colors match well with the measured colors and present red sharp peaks at the galaxy center. The sharp peaks of the colors are mainly shaped by the high metallicity in the galaxy＇s center. Interestingly, the galaxy has steep negative metaUicity gradients, but the trend flattens outwards. This result likely suggests that the center and outer regions of the galaxy formed through different formation processes.

关 键 词：galaxy： elliptical and lenticular -- galaxy： abundances -- galaxy： kine- matic and dynamics -- galaxy： individual （NGC 4636） 

分 类 号：P157[天文地球—天文学] P412.15