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elliptical galaxies with Emission Lines from the Sloan Digital Sky Survey

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Chinese Journal of Astronomy and Astrophysics 2006年第1期6卷 15-24页

作者： Ying-He Zhao Qiu-Sheng Gu Zhi-Xin Peng Lei Shi Xin-Lian Luo Qiu-He Peng Department of Astronomy Nanjing University Nanjing 210093

As part of a study of star formation history along the Hubble sequence, we present here the results for 11 elliptical galaxies with strong nebular emission lines. After removing the dilution from the underlying old stellar populations by use of stellar population synthesis model, we derive the accurate fluxes of all the emission lines in these objects, which are then classified, using emission line ratios, into one Seyfert 2, six LINERs and four HII galaxies. We also identify one HII galaxy （A1216＋04） as a hitherto unknown Wolf-Rayet galaxy from the presence of the WolfRayet broad bump at 4650A. We propose that the star-forming activities in elliptical galaxies are triggered by either galaxy-galaxy interaction or the merging of a small satellite/a massive star cluster, as has been suggested by recent numerical simulations.

关键词： galaxies: elliptical and lenticular cD galaxies: starburst - galaxies:individual: A1212+06 A1216+04 CGCG13-83 IC 225

Revisiting the dichotomy of early-type galaxies

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Research in Astronomy and Astrophysics 2014年第2期14卷 144-158页

作者： Yan-Qin He Cai-Na Hao Xiao-Yang Xia University of Chinese Academy of Sciences National Astronomical Observatories Chinese Academy of Sciences Tianjin Astrophysics Center Tianjin Normal University

We study the relationship between isophotal shapes, central light profiles and kinematic properties of early-type galaxies （ETGs） based on a compiled sample of 184 ETGs. These sample galaxies are included in Data Release 8 of the Sloan Digital Sky Survey and have central light profiles and kinematic properties available from the literature, which were compiled from observations by the Hubble Space Telescope and the ATLAS3D integral-field spectrograph, respectively. We find that there is only a weak correlation between the isophotal shape （a4/a） and the central light profile （within 1 kpc） of ETGs. About two-fifths of ＂core＂ galaxies have disky isophotes, and one-third of ＂power-law＂ galaxies are boxy. Our statistical results also show that there are weak correlations between galaxy luminosity and dynamical mass with a4/a, but such correlations are tighter with a central light profile. Moreover, no clear link has been found between the isophotal shape and the Sersic index. Comparisons show that there are similar correlations between a4/a and ellipticity, and between a4/a and specific angular momentum ARo/2 for ＂power-law＂ ETGs, but there are no such correlations for ＂core＂ ETGs. Therefore, we speculate that the bimodal classifications of ETGs are not as simple as previously thought, though we also find that the disky ETGs with highest a4/a are more elongated and fast rotators.

关键词： galaxies: elliptical and lenticular cD -- galaxies: kinematics and dynamics -- galaxies: photometry -- galaxies: structure

Clumpy metal concentrations in elliptical galaxies NGC 4374 and NGC 4636

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Research in Astronomy and Astrophysics 2010年第3期10卷 220-226页

作者： Hai-Guang Xu Jun-Hua Gu Li-Yi Gu Zhong-Li Zhang Yu Wang Tao An Department of Physics Shanghai Jiao Tong University Shanghai 200240 China Max-Planck Institut fur Astrophysik D-85740 Garching Germany Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai 200030 China

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