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Date and Time of the Query: 2019-08-25 T19:32:22 PDT
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For refcode 1995A&A...298..405S:
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Copyright by European Southern Observatory (ESO). Reproduced by permission
1995A&A...298..405S Relics of dissipational merging and past violent starbursts in elliptical galaxies - the gE galaxy NGC 4365 P. Surma and R. Bender Institute of Astronomy, Cambridge CB3 OHA, UK Universitatssternwarte Munchen, D-8 1679 Munchen, Germany Landessternwarte Konigstuhl, D-69 117 Heidelberg, Germany Received 26 August 1994 / Accepted 17 November 1994 Abstract. The Virgo elliptical galaxy NGC 4365 harbours a kinematically decoupled, counter-rotating core region. Its line-of-sight integrated velocity distributions are studied along 3 spectroscopic axes using Gauss-Hermite moments and double-gaussian line models. Stellar populations are investigated through high-resolution (B - R) colour photometry and spectroscopic absorption line indices Mg2 , H{beta} and <Fe> , which are compared to population models of Worthey (1992). We find consistent evidences for a distinct core population C of stars with disk or bar-like structure, high rotation velocity and low kinematic temperature (v/{sigma} = 1.3), flattened density distribution (e_c_ = 0.39_/-0.07 versus e_spheroid_ = 0.21... 0.245) and a mass content of at least (8.1 +/- 2.5) x 10^9^ M_sun_. The metallicity of this core population shows an excessively flattened distribution (relative to the isophotes) and reaches values of at least 2.3 Z_sun_ at a population age of about < (7 +/- 1.5) Gyr. We favour a formation scenario with gas included in early hierarchical or late major mergers, where the gas is subject to strong dissipation effects and chemical enrichment and produces a violent starburst of order 10^2^ M_sun_/yr. Our line indices show the well-known enhanced (Mg/Fe] of massive Es, but furthermore excessive enhancement of magnesium relative to iron in the innermost core region. This is interpreted as confirming evidence for a violent gaseous merger which probably over-produced SN II versus SN Ia due to a top-heavy IMF or because of its burst-like star formation history. Key words: galaxies: elliptical and lenticular, cD - galaxies: kinematics and dynamics - galaxies: abundances - galaxy formation - galaxies: interactions - galaxies: individual: 4365
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