Clumpy metal concentrations in elliptical galaxies NGC 4374 and NGC 4636  

作　　者：Hai-Guang Xu Jun-Hua Gu Li-Yi Gu Zhong-Li Zhang Yu Wang Tao An 

机构地区：[1]Department of Physics, Shanghai Jiao Tong University, Shanghai 200240, China [2]Max-Planck Institut fur Astrophysik, D-85740 Garching, Germany [3]Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030, China

出　　处：《Research in Astronomy and Astrophysics》2010年第3期220-226,共7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(Grant Nos.10503008,10673008,10878001 and 10973010);the Ministry of Science and Technology of China(Grant No.2009CB824900/2009CB24904);the Ministry of Education of China(the NCET Program)

摘　　要：We present a high spatial resolution study of metal distributions in the nearby, gas-rich elliptical galaxies NGC 4374 and NGC 4636 with the Chandra ACIS archive data. We define the hardness ratio HRFeL as the ratio of the emission in 0.65- 1.4 keV to that in 0.3-0.6 keV and 1.4-3.5 keV （after the magnesium and silicon lines are excluded）, and HRcont as the ratio of the emission in 1.4-3.5keV to that in 0.3- 0.6 keV, so that the HRFeL and HRcont maps can be used to trace the iron abundance and gas temperature distributions, respectively. By applying the a Trous wavelet algorithm to the obtained emission hardness ratio maps, we reveal that the HRFeL distributions are highly irregular, exhibiting strong spatial variations on 0.1-1 Re scales, which do not follow the HRcont distributions. Since the effect of temperature variation is small, we conclude that most of the high-HRFeL regions are very likely to possess higher abundances than the ambient gas. We also find that these high-HRFeL substructures are not associated with either the LMXB or globular cluster populations, thus their origins should be related to AGN activity or mergers.We present a high spatial resolution study of metal distributions in the nearby, gas-rich elliptical galaxies NGC 4374 and NGC 4636 with the Chandra ACIS archive data. We define the hardness ratio HRFeL as the ratio of the emission in 0.65- 1.4 keV to that in 0.3-0.6 keV and 1.4-3.5 keV （after the magnesium and silicon lines are excluded）, and HRcont as the ratio of the emission in 1.4-3.5keV to that in 0.3- 0.6 keV, so that the HRFeL and HRcont maps can be used to trace the iron abundance and gas temperature distributions, respectively. By applying the a Trous wavelet algorithm to the obtained emission hardness ratio maps, we reveal that the HRFeL distributions are highly irregular, exhibiting strong spatial variations on 0.1-1 Re scales, which do not follow the HRcont distributions. Since the effect of temperature variation is small, we conclude that most of the high-HRFeL regions are very likely to possess higher abundances than the ambient gas. We also find that these high-HRFeL substructures are not associated with either the LMXB or globular cluster populations, thus their origins should be related to AGN activity or mergers.

关 键 词：galaxies： elliptical and lenticular cD -- galaxies： individual （NGC 4374 NGC 4636） -- galaxies： ISM -- ISM： abundances -- X-rays： galaxies 

分 类 号：P157[天文地球—天文学] TQ153[化学工程—电化学工业]