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2016MNRAS.461.2068K - Mon. Not. R. Astron. Soc., 461, 2068-2076 (2016/September-2)

Stellar counter-rotation in lenticular galaxy NGC 448.


Abstract (from CDS):

The counter-rotation phenomenon in disc galaxies directly indicates a complex galaxy assembly history which is crucial for our understanding of galaxy physics. Here, we present the complex data analysis for a lenticular galaxy NGC 448, which has been recently suspected to host a counter-rotating stellar component. We collected deep long-slit spectroscopic observations using the Russian 6-m telescope and performed the photometric decomposition of Sloan Digital Sky Survey archival images. We exploited (i) a non-parametric approach in order to recover stellar line-of-sight velocity distributions and (ii) a parametric spectral decomposition technique in order to disentangle stellar population properties of both main and counter-rotating stellar discs. Our spectral decomposition stays in perfect agreement with the photometric analysis. The counter-rotating component contributes ≃30 per cent to the total galaxy light. We estimated its stellar mass to be 9.0^{+2.7}_{-1.8}×10^{9} M_☉. The radial scalelength of counter-rotating disc is ≃3 times smaller than that of the main disc. Both discs harbour old stars but the counter-rotating components reveal a detectable negative age gradient that might suggest an extended inside-out formation during 3...4 Gyr. The counter-rotating disc hosts more metal-rich stars and possesses a shallower metallicity gradient with respect to the main disc. Our findings rule out cosmological filaments as a source of external accretion which is considered as a potential mechanism of the counter-rotating component formation in NGC 448, and favour the satellite merger event with the consequent slow gas accretion.

Abstract Copyright: © 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society

Journal keyword(s): galaxies: elliptical and lenticular, cD - galaxies: evolution - galaxies: individual: NGC 448 - galaxies: ISM - galaxies: kinematics and dynamics - galaxies: kinematics and dynamics

Simbad objects: 12

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